Search tips
Search criteria

Results 1-25 (983511)

Clipboard (0)

Related Articles

1.  Ubc9 Mediates Nuclear Localization and Growth Suppression of BRCA1 and BRCA1a Proteins 
Journal of Cellular Physiology  2011;226(12):3355-3367.
BRCA1 gene mutations are responsible for hereditary breast and ovarian cancers. In sporadic breast tumors, BRCA1 dysfunction or aberrant subcellular localization is thought to be common. BRCA1 is a nuclear–cytoplasm shuttling protein and the reason for cytoplasmic localization of BRCA1 in young breast cancer patients is not yet known. We have previously reported BRCA1 proteins unlike K109R and cancer-predisposing mutant C61G to bind Ubc9 and modulate ER-α turnover. In the present study, we have examined the consequences of altered Ubc9 binding and knockdown on the subcellular localization and growth inhibitory function of BRCA1 proteins. Our results using live imaging of YFP, GFP, RFP-tagged BRCA1, BRCA1a and BRCA1b proteins show enhanced cytoplasmic localization of K109 R and C61G mutant BRCA1 proteins in normal and cancer cells. Furthermore, down-regulation of Ubc9 in MCF-7 cells using Ubc9 siRNA resulted in enhanced cytoplasmic localization of BRCA1 protein and exclusive cytoplasmic retention of BRCA1a and BRCA1b proteins. These mutant BRCA1 proteins were transforming and impaired in their capacity to inhibit growth of MCF-7 and CAL51 breast cancer cells. Interestingly, cytoplasmic BRCA1a mutants showed more clonogenicity in soft agar and higher levels of expression of Ubc9 than parental MCF7 cells. This is the first report demonstrating the physiological link between cytoplasmic mislocalization of mutant BRCA1 proteins, loss of ER-α repression, loss of ubiquitin ligase activity and loss of growth suppression of BRCA1 proteins. Thus, binding of BRCA1 proteins to nuclear chaperone Ubc9 provides a novel mechanism for nuclear import and control of tumor growth.
PMCID: PMC3329759  PMID: 21344391
2.  BRCA1 and BRCA2 mutations in central and southern Italian patients 
Breast Cancer Research : BCR  2000;2(4):307-310.
Protein truncation test (PTT) and single-strand conformation polymorphism (SSCP) assay were used to scan the BRCA1 and BRCA2 genes in 136 unrelated Italian breast/ovarian cancer patients. In the sample tested, BRCA1 and BRCA2 equally contributed to site-specific breast cancer patients who reported one to two breast cancer-affected first-/ second-degree relative(s) or who were diagnosed before age 40 years in the absence of a family history of breast/ovarian cancer. BRCA1 and BRCA2 mutations were mostly found in patients with disease diagnosis before and after age 50 years, respectively. Moreover, in cases with familial clustering of site-specific breast cancer, BRCA1 mostly accounted for tumours diagnosed before age 40 years and BRCA2 for tumours diagnosed after age 50 years. The BRCA1 and BRCA2 mutation spectrum was consistent with a lack of significant founder effects in the sample of patients studied.
Germline BRCA1 and BRCA2 mutations account for most hereditary breast/ovarian cancers and are associated with male breast cancer. Furthermore, constitutional mutations in these genes may occur in breast/ovarian cancer patients that do not meet stringent criteria of autosomal-dominant predisposition. The relevance of BRCA1 and BRCA2 mutations in such patients is still debated.
We sought to determine the impact of BRCA1 and BRCA2 mutations in a population of patients from central and southern Italy. We analyzed the BRCA1 and BRCA2 coding regions in 136 unrelated probands: 117 females with breast/ovarian cancer and 19 males with breast cancer. This population of patients was mostly representative of cases who are at risk for hereditary susceptibility, but who do not meet stringent criteria of autosomal-dominant predisposition.
Probands, subclassified as follows, were consecutively recruited depending on informed consent from patients attending breast cancer clinics in Rome and Naples. Selection criteria for females were as follows: breast cancer with breast cancer family history [one to two first-/second-degree relative(s), n = 55]; breast cancer diagnosed before age 40 years (no breast/ovarian cancer family history, n = 28); bilateral breast cancer (regardless of age and family history, n =10); breast cancer associated with gastrointestinal, pancreatic or uterine cancers [synchronous/metachronous or in first-degree relative(s), n = 9]; breast or ovarian cancer with family history of breast-ovarian/ovarian cancer (at least 1 first-/ second-degree relative, n = 10); and ovarian cancer with no breast/ovarian cancer family history (n = 5). Males with breast cancer were recruited regardless of age and family history. BRCA1 exon 11 and BRCA2 exons 10 and 11 were screened by PTT. Coding BRCA1 exons 2, 3, 5-10 and 12-24 and BRCA2 exons 2-9 and 12-27 were screened by SSCP. Primers are listed in Table 1. In 27 cases, analyzed by PTT along the entire BRCA1 coding sequence, BRCA1 SSCP analysis was limited to exons 2, 5, 20 and 24. Mutations were verified by sequence analysis on two independent blood samples.
Deleterious germline BRCA1/BRCA2 mutations were detected in 11 out of 136 cases (8%). Only three BRCA2 mutations were novel. One BRCA2 mutation recurred in two unrelated probands. Table 2 shows the mutations and data concerning carriers and their families. Table 3 shows correlations between BRCA1/BRCA2 mutations and sex, age at disease diagnosis and familial clustering of breast/ovarian cancer in the total patient population. Table 4 shows the proportions of BRCA1 and BRCA2 mutations in females with site-specific breast and breast-ovarian/ovarian cancer. Table 5 shows the frequency of BRCA1/BRCA2 mutations in males. BRCA1 and BRCA2 mutations, respectively, accounted for four out of 68 (6%) and one out of 68 (1%) cases diagnosed before age 50 years, and for one out of 68 (1%) and five out of 68 (7%) cases diagnosed after age 50 years. BRCA1 mutations were found in five out of 117 females (4%) and in none of 19 males (0%), and BRCA2 mutations were found in four out of 117 females (3%) and in two out of 19 males (10%). The proportions of BRCA1 and BRCA2 mutations coincided in site-specific female breast cancers (four out of 102; ie 4% each). BRCA1 and BRCA2 equally contributed to female breast cancers, with no familial clustering in those diagnosed before age 40 years (one out of 28; 4% each), and to female breast cancers, all ages, with familial clustering in one to two relatives (three out of 55; ie 5% each). In the latter subset of cases, BRCA1 mostly accounted for tumours diagnosed before age 40 years (two out of eight; 25%), and BRCA2 for tumours diagnosed after age 50 years (three out of 34; 9%). Regardless of family history, the respective contributions of BRCA1 and BRCA2 to site-specific female breast cancers diagnosed before age 40 years were 8% (three out of 36) and 3% (one out of 36). One BRCA1 mutation was detected among the 15 female probands from breast-ovarian/ovarian cancer families (7%). Among male breast cancers, BRCA2 mutations were identified in one out of five (20%) cases with family history and in one out of 14 (7%) apparently sporadic cases. No BRCA1 or BRCA2 mutations were found in female probands with nonfamilial bilateral breast cancer (10 cases) or in those with breast cancer associated with gastrointestinal, pancreatic or uterine cancers, synchronous/metachronous or in first-degree relative(s) (nine cases). These cases were all diagnosed after age 40 years.
Our results indicate a lack of relevant founder effects for BRCA1- and BRCA2-related disease in the sample of patients studied, which is consistent with other Italian studies and with ethnical and historical data. Overall, the contribution of BRCA1 and BRCA2 to breast/ovarian cancer in Italian patients appears to be less significant than in patients from communities with founder mutations. The present study is in agreement with direct estimates on other outbred populations, indicating that 7-10% of all female breast cancers that occur in patients aged under 40 years are due to BRCA1/BRCA2.
We found that BRCA1 and BRCA2 equally contributed to site-specific breast cancers who had one/two breast cancer-affected first-/second-degree relative(s) or who were diagnosed within age 40 years in the absence of family history. This is consistent with recent data that indicated that the respective frequencies of BRCA1 and BRCA2 mutations are comparable in early onset breast cancer. Considering the total population of patients analyzed here, however, BRCA1 and BRCA2 mutations were mostly found in cases with disease diagnosis before and after age 50 years, respectively. Moreover, in cases with familial clustering of site-specific breast cancer, BRCA1 mostly accounted for tumours diagnosed before age 40 years, and BRCA2 for tumours diagnosed after age 50 years. This is in agreement with a trend, which has been observed in other populations, for the proportion of cases with BRCA2 mutations to increase, and the proportion with mutations in BRCA1 to decrease, as the age at cancer onset increases.
As in other studies, the frequency of BRCA1/BRCA2 mutations taken together was lower than the estimated frequencies at comparable ages for all susceptibility alleles derived from the Contraceptive and Steroid Hormones (CASH) study. The discrepancy between direct data deriving from BRCA1/BRCA2 mutational analysis and CASH estimates could be due to several factors, including contribution of gene(s) other than BRCA1/BRCA2, differences between populations and relative insensitivity of mutational screening. Only BRCA1 mutations were found in breast/ovarian and site-specific ovarian cancer families. BRCA2, but not BRCA1 mutations were found in the male breast cancers. The overall proportion of males with BRCA2 mutations was high when compared with data from other studies on outbred populations, but was low compared with data from populations with founder effects.
The present results should be regarded as an approximation, because the following types of mutation are predicted to escape detection by the screening strategy used: mutations in noncoding regions; missense mutations within BRCA1 exon 11 and BRCA2 exons 10 and 11; large gene deletions; and mutations within the first and last 180 nucleotides of the amplicons analyzed by PTT.
PMCID: PMC13918  PMID: 11056688
BRCA1; BRCA2; breast; carcinoma; germline mutations; Italy
3.  Increased cell survival by inhibition of BRCA1 using an antisense approach in an estrogen responsive ovarian carcinoma cell line 
Breast Cancer Research  2000;2(2):139-148.
We tested the hypothesis that BRCA1 may play a role in the regulation of ovarian tumor cell death as well as the inhibition of ovarian cell proliferation. Introduction of BRCA1 antisense retroviral constructs into BG-1 estrogen-dependent ovarian adenocarcinoma cells resulted in reduced BRCA1 expression. BRCA1 antisense pooled populations and derived subclones were able to proliferate in monolayer culture without estrogen, whereas control cells began to die after 10 days of estrogen deprivation. In addition, both populations and subclones of BRCA1 antisense infected cells demonstrated a growth advantage in monolayer culture in the presence of estrogen and were able to proliferate in monolayer culture without estrogen, while control cells did not. Furthermore, clonal studies demonstrated that reduced levels of BRCA1 protein correlated with growth in soft agar and greater tumor formation in nude mice in the absence of estrogen. These data suggest that reduction of BRCA1 protein in BG-1 ovarian adenocarcinoma cells may have an effect on cell survival during estrogen deprivation both in vitro and in vivo.
Germline mutations in the breast and ovarian cancer susceptibility gene BRCA1, which is located on chromosome 17q21, are associated with a predisposition to the development of cancer in these organs [1,2]. No mutations in the BRCA1 gene have been detected in sporadic breast cancer cases, but mutations have been detected in sporadic cases of ovarian cancer [3,4]. Although there is debate regarding the level of cancer risk associated with mutations in BRCA1 and the significance of the lack of mutations in sporadic tumors, it is possible that alterations in the function of BRCA1 may occur by mechanisms other than mutation, leading to an underestimation of risk when it is calculated solely on the basis of mutational analysis. Such alterations cannot be identified until the function and regulation of BRCA1 are better understood.
The BRCA1 gene encodes a 220-kDa nuclear phosphoprotein that is regulated in response to DNA damaging agents [5,6,7] and in response to estrogen-induced growth [8,9,10,11]. Germline mutations that cause breast and ovarian cancer predisposition frequently result in truncated and presumably inactive BRCA1 protein [12].
BG-1 cells were derived from a patient with stage III, poorly differentiated ovarian adenocarcinoma [13]. This cell line, which expresses wild-type BRCA1, is estrogen responsive and withdrawal of estrogen results in eventual cell death. Previous studies suggest that BRCA1 is stimulated as a result of estrogen treatment [8,9,10,11], and also that BRCA1 may be involved in the cell death process [14]. Therefore, we examined the effect of reduction of BRCA1 levels in BG-1 cells on the cellular response to hormone depletion as well as estrogen stimulation. The results suggest that reduced levels of BRCA1 correlates with a survival advantage when BG-1 cells are placed under growth-restrictive and hormone-depleted conditions. In optimum growth conditions, significantly reduced levels of BRCA1 correlates with enhanced growth both in vitro and in vivo.
To test the hypothesis that BRCA1 may play a role in the regulation of ovarian tumor cell death as well as in the inhibition of ovarian cell proliferation.
Materials and methods:
The estrogen receptor-positive, BG-1 cell line [13], which contains an abundant amount of estrogen receptors (600 fmoles/100 μg DNA), was infected using a pLXSN retroviral vector (provided by AD Miller) containing an inverted partial human cDNA 900-base-pair sequence of BRCA1 (from nucleotide 121 in exon 1 to nucleotide 1025 in exon 11, accession #U14680). After 2 weeks of selection in 800 μg/ml of geneticin-G418 (Gibco/Life Technologies, Gaithersburg, MD, USA), BG-1 G418-resistant colonies were pooled, or individually isolated, and assayed for growth in the presence or absence of supplemented estrogen. Virally infected pooled populations of BG-1 cells were examined for BRCA1 message levels by ribonuclease protection assay (Fig. 1a). BRCA1 ribonuclease protection probe was made using an in vitro transcription kit (Ambion, Inc, Austin, TX, USA) as previously described [10] and derived clones were tested for protein levels by Western blot analysis using an anti-BRCA1 (Oncogene Research, Ab-1, Cambridge, MA, USA) antibody. Growth curve analysis of Infected populations and were pretreated for 5 days in phenol red-free, Dulbecco's modified eagle medium (DMEM)/F-12 medium (Gibco/Life Technologies) supplemented with 10% charcoal/dextran treated serum (Hyclone, Logan, UT, USA), then plated at 2.5 × 106 cells per 100mm dish in triplicate in the absence or presence of estrogen (10-8 mol/l; 17β-Estradiol; 1,3,5 (10) - Estratriene 3,17β-diol; Sigma, St Louis, MO, USA). For soft agar assay, clones were plated into 10 60-mm dishes at 1 × 105 cells/dish containing 0.3% bactopeptone agar with or without added estrogen (10-8 mol/l) in phenol red-free medium with 10% stripped serum in order to test for anchorage independent growth. BG-1 infected clones were tested for tumorigenicity by injection of cells (106 cells in 0.1cm2 50% matrigel; Collaborative Biomedical Products, Bedford, MA, USA) into subcutaneous sites in 6-week-old athymic Ncr-nude mice (NCI Animal Program, Bethesda, MD, USA) that were ovariectomized at approximately 4 weeks of age. Half of the ovariectomized mice received an implanted 0.18mg estrogen 60-day pellet (Innovative Research of America, Sarasota, FL, USA).
Antisense technology was effective in decreasing both RNA and protein levels of BRCA1 in the BG-1 human ovarian adenocarcinoma cells. BRCA1 antisense-infected populations contained significantly less BRCA1 message than control LXSN-infected pools and selected clones contained varying reduced levels of BRCA1 protein compared with control clones (Figs 1a and 1b).
Three independent BRCA1 antisense-infected cultures demonstrated a resistance to cell death induced by withdrawal from estrogen over a 6- to 20-day period (Fig. 2a). The BRCA1 antisense population also exhibited a threefold to sixfold increase in cell growth compared with control cells in the presence of estrogen treatment. BG-1 BRCA1 antisense clones demonstrated a similar response to pooled population studies, enhanced growth with estrogen, and failure to die upon estrogen depletion (Fig. 2b).
The BRCA1 antisense clones were further examined for other associated tumorigenic properties. All of the antisense clones were able to form colonies in soft agar (2-23 colonies per 104 cells plated; data not shown), whereas control clones were deficient in their ability to form colonies (0-0.8 colonies per 104 cells plated). Table 1 shows, in the presence of estrogen, the clone with the lowest levels of BRCA1 (AS-4) produced significantly more colonies (133 ± 17.9 colonies per 104 cells plated) than the control clone (NEO; 6 ± 3.1 colonies per 104 cells plated). Clones AS-4 and NEO were also injected with matrigel subcutaneously into ovariectomized athymic mice. Almost twice as many sites were positive for the AS-4 clone (14 out of 14) as for the NEO clone (eight out of 14) 42 days after injection. In addition, BRCA1 antisense tumors averaged twice the size of control tumors. The BRCA1 reduced cells also formed tumors with half the latency of control cells in the presence of implanted estrogen (11 days versus 21 days until tumor formation).
The present studies show that reduction in BRCA1 levels, using an antisense retroviral vector in the estrogen dependent BG-1 ovarian carcinoma cell line, contributes to confirmation of the hypothesis that BRCA1 plays a pivotal role in the balance between cell death and cell proliferation. BRCA1 RNA and protein levels were successfully reduced in populations and isolated clones of antisense infected BG-1 cells. Decreased BRCA1 levels rescued the BG-1 cells from growth arrest or cell death in adverse growth conditions in monolayer or soft agar conditions. Furthermore, a BRCA1 antisense clone that had significantly low levels of BRCA1 protein was able to form twice as many tumors in ovariectomized nude mice with a decreased latency compared with a control clone.
In multicellular mammalian organisms, a balance between cell proliferation and cell death is extremely important for the maintenance of normal healthy tissues. In support of this hypothesis, it has been shown that p53 and BRCA1 can form stable complexes, and can coactivate p21 and bax genes, which may lead to the activation of the apoptosis pathway [15]. The present data, which show that cells with a reduction of BRCA1 have a survival advantage in conditions where control cells fail to thrive, also supports this hypothesis. BRCA1 levels appear to affect the ability of cells to arrest growth or die in the absence of estrogenic growth-inducing conditions. Although mutations in this gene are uncommon in sporadic breast and ovarian tumors, BRCA1 expression levels and protein levels have been found to be reduced in sporadic human breast carcinomas [16,17,18,19]. In addition it has been demonstrated [20] that hormone-dependent tumors such as breast and ovarian cancers have a decreased ability to undergo apoptosis. Other mechanisms involving gene regulation may allow for decreased expression of BRCA1 in sporadic tumors. The response of BRCA1 mRNA and protein levels to mitogens and hormones in vitro suggests that BRCA1 may play a role in regulation of cell growth or maintenance [21]. The BRCA1 gene product may be involved in the regulation of hormone response pathways, and the present results demonstrate that loss of BRCA1 may result in loss of inhibitory control of these mitogenic pathways. These studies show that reduction in BRCA1 mRNA and protein can result in increased proliferation of BG-1 ovarian cancer cells in both in vitro and in vivo conditions, suggesting that BRCA1 may normally be acting as a growth inhibitor. Low BRCA1 levels found in sporadic cancers may be an important factor in tumorigenesis. The present data suggest that diminished levels of BRCA1 not only accelerate proliferation in the BG-1 ovarian carcinoma cell line, but also appear to promote tumorigenesis. We propose that the loss or reduction of BRCA1 may predispose a cell population to neoplastic transformation by altering the balance between cell death and proliferation/survival, rendering it more sensitive to secondary genetic changes.
PMCID: PMC13916  PMID: 11056686
antisense; BRCA1; cell death; estrogen; ovarian cancer; proliferation
4.  Selected Aspects of Molecular Diagnostics of Constitutional Alterations in BRCA1 and BRCA2 Genes Associated with Increased Risk of Breast Cancer in the Polish Population 
This study was undertaken to determine: 1) Type and prevalence of founder mutations BRCA1 and BRCA2 genes in Polish families with strong aggregation of breast and/or ovarian cancer. 2) Risk of breast and/or ovarian cancer depending on type of BRCA1 gene mutation. 3) Prevalence of BRCA1 mutation and of other alleles presumably linked with predisposition to breast cancer in unselected Polish patients with breast cancer. 4) Risk of breast cancer in patients with 5972C/T polymorphism that alters the BRCA2 protein structure.
Summary of the results
1. Among 66 families from several regions in Poland with a strong aggregation of breast/ovarian cancer, founder mutation of the BRCA1 gene were disclosed in 34 families and of the BRCA2 gene in on family. Altogether, seven different mutations were disclosed. Five mutations were found in at least two families in this group. The most frequent mutation was 5382insC (18 families), followed by C61G (7 families) and 4153delA (4 families). 2. Among 200 families representative for Poland with strong aggregation of breast/ovarian cancer, mutation of the BRCA1 gene were found in 122 families (61%) and of the BRCA2 gene in seven families (3,5%). 119 out of 122 mutations of the BRCA1 gene (97,5%) were repeatable. Three recurrent mutations of the BRCA1 gene (5382insC, C61G, 4153delA) characteristic for the Polish population were disclosed in 111 families representing 86% of all pathogenic sequences of this gene. 3. The risk of ovarian cancer in carriers of the three most frequent recurrent mutation of the BRCA1 gene in Poland is similar (OR 43.6 for 5382insC and 50 for 4153delA). The risk of breast cancer is significantly different for 4153delA (OR 1) and for other mutations (OR 10.9). 4. Among 2012 unselected breast cancers diagnosed in hospitals of nine Polish cities, mutations of the BRCA1 gene (5382insC, C61G, 4153delA) were disclosed in 2.9% patients. CHEK2 alternation (1100delC, IVS2+1G>A, I157T) was discovered in 8.1% and NBS1 mutation (657del5) in 0.8% of the patients. The changes were more frequent in the study than the control group. However, the risk of breast cancer was significantly higher for only three of them. Two changes, namely 5382insC and C61G of the BRCA1 gene revealed a high penetrance (OR 6.2 and 15.0, respectively), while I157T of the CHEK2 gene was associated with a low risk of breast cancer (OR 1.4). Mutations of the BRCA1, CHEK2 and NSB1 genes were significantly more frequent in patients with breast cancer diagnosed prior to 50 years of age. The mean age at diagnosis was 47.2 years for carriers of the BRCA1 mutation, 50.7 years for NBS1 and 54.2 for CHEK2. The mean age at diagnosis in the group of patients without any if the mutations described above was 56.1 years. When breast cancer patients with the diagnosis before and after 50 years of age were compared, the greatest difference in the frequency of mutation was revealed for the BRCA1 gene (5.5% vs 1.5%).
BRCA1 mutations were significantly more frequent I familial aggregates of the tumor (10.8%), but were also present in sporadic cases (1.8%). For the CHEK2 and NBS1 genes, there was no correlation between frequency and family history of cancer in probands. 5. A higher frequency of heterozygous carriers of 5972C/T polymorphism of the BRCA2 gene was demonstrated for breast cancer prior to 50 years of age (OR 1.4). the risk of breast cancer prior to 50 years of age was particularly high in 5972T/T homozygote (OR 4.7). This polymorphism was associated with breast cancer notable for intraductal growth.
1. Efficient molecular diagnostics of genetic predisposition to breast/ovarian cancer in Poland could be based on relatively simple tests disclosing some of the most frequent recurrent mutations of the BRCA1 gene. 2. The risk of breast cancer seems to be only slightly higher in carriers of some BRCA1 gene mutations. This finding should be taken into account during work on prevention schemes for carriers of the BRCA1 mutations. 3. 5382insC and C61G mutations of the BRCA1 gene are linked with high risk of breast cancer. Changes in the CHEK2 and NBS1 genes appear to be linked with a higher risk of breast cancers, particularly at young age. However, penetrance in this case is low. All patients with breast cancer should be tested for BRCA1 gene mutations because the percentage of mutations is also high in patients older than 50 years of age or without familiar aggregation of breast/ovarian cancer. 4. Polymorphic changes in the BRCA2 gene sequence previously regarded as non-pathogenic may nevertheless predispose, homozygotes in particular, to breast cancer. Apparently, the recessive character of these changes is responsible for the negative family history in most cases. The use of DNA tests is the only way to disclose increased risk of breast cancer in carriers of the 5972T/T mutation.
PMCID: PMC4177211  PMID: 20223018
breast cancer; ovarian cancer; inherited predisposition; BRCA1; BRCA2
5.  Transcriptional autoregulation by BRCA1 
Cancer research  2010;70(2):532-542.
The BRCA1 gene product plays numerous roles in regulating genome integrity. Its ability to participate in the assembly of various super-molecular complexes in response to DNA damage has been extensively studied, however much less is understood about BRCA1’s direct role as a gene-specific transcriptional co-regulator. BRCA1 loss or mutation is highly associated with hereditary breast and ovarian cancer and numerous reports show that altered levels of BRCA1 expression are frequently found in sporadic forms of breast cancer, suggesting that control of BRCA1 transcription may also play a significant role in tumorigenesis. In this report we provide evidence of a stunning linkage between BRCA1’s role as a transcriptional co-regulator and the control of its expression via an auto-regulatory transcriptional loop. BRCA1 assembles with complexes containing E2F-1 and RB to form a repressive multi-component transcriptional complex that inhibits BRCA1 promoter transcription. This complex is disrupted by genotoxic stress resulting in the displacement of BRCA1 protein from the BRCA1 promoter and subsequent up-regulation of BRCA1 transcription. Cells depleted of BRCA1 in vivo show up-regulation of BRCA1 transcripts while cells over-expressing BRCA1 show BRCA1 transcript down-regulation. Tandem chromatin immmuno-precipitation studies demonstate that BRCA1 is regulated by a dynamic co-regulatory complex containing BRCA1, E2F1 and Rb at the BRCA1 promoter that is disrupted by DNA damaging agents to increase its transcription. These findings define a novel transcriptional mechanism in which BRCA1 expression is controlled by an autoregulated homeostasis that selectively titrates its levels to maintain genome integrity in response to genotoxic insult.
PMCID: PMC2952428  PMID: 20068145
BRCA1; cell cycle; DNA damage; transcription
6.  Activated networking of platelet activating factor receptor and FAK/STAT1 induces malignant potential in BRCA1-mutant at-risk ovarian epithelium 
It is essential to understand the molecular basis of ovarian cancer etiology and tumor development to provide more effective preventive and therapeutic approaches to reduce mortality. Particularly, the molecular targets and pathways involved in early malignant transformation are still not clear. Pro-inflammatory lipids and pathways have been reported to play significant roles in ovarian cancer progression and metastasis. The major objective of this study was to explore and determine whether platelet activating factor (PAF) and receptor associated networking pathways might significantly induce malignant potential in BRCA1-mutant at-risk epithelial cells.
BRCA1-mutant ovarian epithelial cell lines including (HOSE-636, HOSE-642), BRCA1-mutant ovarian cancer cell (UWB1.289), wild type normal ovarian epithelial cell (HOSE-E6E7) and cancerous cell line (OVCA429), and the non-malignant BRCA1-mutant distal fallopian tube (fimbria) tissue specimens were used in this study. Mutation analysis, kinase microarray, western blot, immune staining, co-immune precipitation, cell cycle, apoptosis, proliferation and bioinformatic pathway analysis were applied.
We found that PAF, as a potent pro-inflammatory mediator, induced significant anti-apoptotic effect in BRCA1-mutant ovarian surface epithelial cells, but not in wild type HOSE cells. With kinase microarray technology and the specific immune approaches, we found that phosphor-STAT1 was activated by 100 nM PAF treatment only in BRCA1-mutant associated at-risk ovarian epithelial cells and ovarian cancer cells, but not in BRCA1-wild type normal (HOSE-E6E7) or malignant (OVCA429) ovarian epithelial cells. Co-immune precipitation revealed that elevated PAFR expression is associated with protein-protein interactions of PAFR-FAK and FAK-STAT1 in BRCA1-mutant ovarian epithelial cells, but not in the wild-type control cells.
Previous studies showed that potent inflammatory lipid mediators such as PAF and its receptor (PAFR) significantly contribute to cancer progression and metastasis. Our findings suggest that these potent inflammatory lipids and receptor pathways are significantly involved in the early malignant transformation through PAFR-FAK-STAT1 networking and to block apoptosis pathway in BRCA1 dysfunctional at-risk ovarian epithelium.
PMCID: PMC2903602  PMID: 20576130
7.  Localization of BRCA1 protein in breast cancer tissue and cell lines with mutations 
The breast and ovarian cancer susceptibility gene (BRCA1) encodes a tumor suppressor. The BRCA1 protein is found primarily in cell nuclei and plays an important role in the DNA damage response and transcriptional regulation. Deficiencies in DNA repair capabilities have been associated with higher histopathological grade and worse prognosis in breast cancer.
In order to investigate the subcellular distribution of BRCA1 in tumor tissue we randomly selected 22 breast carcinomas and tested BRCA1 protein localization in frozen and contiguous formalin-fixed, paraffin embedded (FFPE) tissue, using pressure cooker antigen-retrieval and the MS110 antibody staining. To assess the impact of BRCA1 germline mutations on protein localization, we retrospectively tested 16 of the tumor specimens to determine whether they contained the common Ashkenazi Jewish founder mutations in BRCA1 (185delAG, 5382insC), and BRCA2 (6174delT). We also compared co-localization of BRCA1 and nucleolin in MCF7 cells (wild type) and a mutant BRCA1 cell line, HCC1937 (5382insC).
In FFPE tissue, with MS110 antibody staining, we frequently found reduced BRCA1 nuclear staining in breast tumor tissue compared to normal tissue, and less BRCA1 staining with higher histological grade in the tumors. However, in the frozen sections, BRCA1 antibody staining showed punctate, intra-nuclear granules in varying numbers of tumor, lactating, and normal cells. Two mutation carriers were identified and were confirmed by gene sequencing. We have also compared co-localization of BRCA1 and nucleolin in MCF7 cells (wild type) and a mutant BRCA1 cell line, HCC1937 (5382insC) and found altered sub-nuclear and nucleolar localization patterns consistent with a functional impact of the mutation on protein localization.
The data presented here support a role for BRCA1 in the pathogenesis of sporadic and inherited breast cancers. The use of well-characterized reagents may lead to further insights into the function of BRCA1 and possibly the further development of targeted therapeutics.
PMCID: PMC3720266  PMID: 23855721
Breast cancer; BRCA1 mutations; Frozen section immunohistology; Nucleolar localization
8.  Interplay between BRCA1 and RHAMM Regulates Epithelial Apicobasal Polarization and May Influence Risk of Breast Cancer 
Maxwell, Christopher A. | Benítez, Javier | Gómez-Baldó, Laia | Osorio, Ana | Bonifaci, Núria | Fernández-Ramires, Ricardo | Costes, Sylvain V. | Guinó, Elisabet | Chen, Helen | Evans, Gareth J. R. | Mohan, Pooja | Català, Isabel | Petit, Anna | Aguilar, Helena | Villanueva, Alberto | Aytes, Alvaro | Serra-Musach, Jordi | Rennert, Gad | Lejbkowicz, Flavio | Peterlongo, Paolo | Manoukian, Siranoush | Peissel, Bernard | Ripamonti, Carla B. | Bonanni, Bernardo | Viel, Alessandra | Allavena, Anna | Bernard, Loris | Radice, Paolo | Friedman, Eitan | Kaufman, Bella | Laitman, Yael | Dubrovsky, Maya | Milgrom, Roni | Jakubowska, Anna | Cybulski, Cezary | Gorski, Bohdan | Jaworska, Katarzyna | Durda, Katarzyna | Sukiennicki, Grzegorz | Lubiński, Jan | Shugart, Yin Yao | Domchek, Susan M. | Letrero, Richard | Weber, Barbara L. | Hogervorst, Frans B. L. | Rookus, Matti A. | Collee, J. Margriet | Devilee, Peter | Ligtenberg, Marjolijn J. | van der Luijt, Rob B. | Aalfs, Cora M. | Waisfisz, Quinten | Wijnen, Juul | van Roozendaal, Cornelis E. P. | Easton, Douglas F. | Peock, Susan | Cook, Margaret | Oliver, Clare | Frost, Debra | Harrington, Patricia | Evans, D. Gareth | Lalloo, Fiona | Eeles, Rosalind | Izatt, Louise | Chu, Carol | Eccles, Diana | Douglas, Fiona | Brewer, Carole | Nevanlinna, Heli | Heikkinen, Tuomas | Couch, Fergus J. | Lindor, Noralane M. | Wang, Xianshu | Godwin, Andrew K. | Caligo, Maria A. | Lombardi, Grazia | Loman, Niklas | Karlsson, Per | Ehrencrona, Hans | von Wachenfeldt, Anna | Bjork Barkardottir, Rosa | Hamann, Ute | Rashid, Muhammad U. | Lasa, Adriana | Caldés, Trinidad | Andrés, Raquel | Schmitt, Michael | Assmann, Volker | Stevens, Kristen | Offit, Kenneth | Curado, João | Tilgner, Hagen | Guigó, Roderic | Aiza, Gemma | Brunet, Joan | Castellsagué, Joan | Martrat, Griselda | Urruticoechea, Ander | Blanco, Ignacio | Tihomirova, Laima | Goldgar, David E. | Buys, Saundra | John, Esther M. | Miron, Alexander | Southey, Melissa | Daly, Mary B. | Schmutzler, Rita K. | Wappenschmidt, Barbara | Meindl, Alfons | Arnold, Norbert | Deissler, Helmut | Varon-Mateeva, Raymonda | Sutter, Christian | Niederacher, Dieter | Imyamitov, Evgeny | Sinilnikova, Olga M. | Stoppa-Lyonne, Dominique | Mazoyer, Sylvie | Verny-Pierre, Carole | Castera, Laurent | de Pauw, Antoine | Bignon, Yves-Jean | Uhrhammer, Nancy | Peyrat, Jean-Philippe | Vennin, Philippe | Fert Ferrer, Sandra | Collonge-Rame, Marie-Agnès | Mortemousque, Isabelle | Spurdle, Amanda B. | Beesley, Jonathan | Chen, Xiaoqing | Healey, Sue | Barcellos-Hoff, Mary Helen | Vidal, Marc | Gruber, Stephen B. | Lázaro, Conxi | Capellá, Gabriel | McGuffog, Lesley | Nathanson, Katherine L. | Antoniou, Antonis C. | Chenevix-Trench, Georgia | Fleisch, Markus C. | Moreno, Víctor | Pujana, Miguel Angel
PLoS Biology  2011;9(11):e1001199.
Genetic analysis identifies the HMMR gene as a modifier of the breast cancer risk associated with BRCA1 gene mutation, while cell biological analysis of the protein product suggests a function in regulating development of the mammary gland.
Differentiated mammary epithelium shows apicobasal polarity, and loss of tissue organization is an early hallmark of breast carcinogenesis. In BRCA1 mutation carriers, accumulation of stem and progenitor cells in normal breast tissue and increased risk of developing tumors of basal-like type suggest that BRCA1 regulates stem/progenitor cell proliferation and differentiation. However, the function of BRCA1 in this process and its link to carcinogenesis remain unknown. Here we depict a molecular mechanism involving BRCA1 and RHAMM that regulates apicobasal polarity and, when perturbed, may increase risk of breast cancer. Starting from complementary genetic analyses across families and populations, we identified common genetic variation at the low-penetrance susceptibility HMMR locus (encoding for RHAMM) that modifies breast cancer risk among BRCA1, but probably not BRCA2, mutation carriers: n = 7,584, weighted hazard ratio (wHR) = 1.09 (95% CI 1.02–1.16), ptrend = 0.017; and n = 3,965, wHR = 1.04 (95% CI 0.94–1.16), ptrend = 0.43; respectively. Subsequently, studies of MCF10A apicobasal polarization revealed a central role for BRCA1 and RHAMM, together with AURKA and TPX2, in essential reorganization of microtubules. Mechanistically, reorganization is facilitated by BRCA1 and impaired by AURKA, which is regulated by negative feedback involving RHAMM and TPX2. Taken together, our data provide fundamental insight into apicobasal polarization through BRCA1 function, which may explain the expanded cell subsets and characteristic tumor type accompanying BRCA1 mutation, while also linking this process to sporadic breast cancer through perturbation of HMMR/RHAMM.
Author Summary
Mutations in two genes that were initially identified as predisposing carriers to early-onset breast cancer, BRCA1 and BRCA2, cause similar perturbations in cellular responses to DNA damage but predispose carriers to distinct tumor types. Thus, the two genes may trigger different carcinogenic processes. We have used genetic analyses of affected families to uncover additional genetic variation that is linked to the risk of developing cancer for carriers of BRCA1 mutations. This variation falls within a centrosomal gene, named HMMR. The protein product of HMMR, which is called RHAMM, works in concert with BRCA1 to regulate the structure of normal breast cells as they grow and become polarized. This polarization process depends upon a balance between the activities of BRCA1 and the Aurora kinase A, with the kinase opposing BRCA1 function and promoting growth. Our findings provide new insights into the mechanism through which BRCA1 may promote commitment of initially bipotent mammary cells towards the luminal lineage, and how loss of this function may predispose cells to become breast tumors of a basal-like type.
PMCID: PMC3217025  PMID: 22110403
9.  Mitochondrial localization, ELK-1 transcriptional regulation and Growth inhibitory functions of BRCA1, BRCA1a and BRCA1b proteins 
Journal of cellular physiology  2009;219(3):634-641.
BRCA1 is a tumor suppressor gene that is mutated in families with breast and ovarian cancer. Several BRCA1 splice variants are found in different tissues, but their subcellular localization and functions are poorly understood at the moment. We previously described BRCA1 splice variant BRCA1a to induce apoptosis and function as a tumor suppressor of triple negative breast, ovarian and prostate cancers. In this study we have analyzed the function of BRCA1 isoforms (BRCA1a and BRCA1b) and compared them to the wild type BRCA1 protein using several criteria like studying expression in normal and tumor cells by RNase protection assays, sub cellular localization/fractionation by immunofluorescence microscopy and western blot analysis, transcription regulation of biological relevant proteins and growth suppression in breast cancer cells. We are demonstrating for the first time that ectopically expressed GFP-tagged BRCA1, BRCA1a, and BRCA1b proteins are localized to the mitochondria, repress ELK-1 transcriptional activity and possess antiproliferative activity on breast cancer cells. These results suggest that the exon 9,10 and 11 sequences (aa 263 – 1365) which contain two nuclear localization signals, p53, Rb, c-Myc, γ- tubulin, Stat, Rad 51, Rad 50 binding domains, angiopoietin-1 repression domain are not absolutely required for mitochondrial localization and growth suppressor function of these proteins. Since mitochondrial dysfunction is a hallmark of cancer, we can speculate that the mitochondrial localization of BRCA1 proteins may be functionally significant in regulating both the mitochondrial DNA damage as well as apoptotic activity of BRCA1 proteins and mislocalization causes cancer.
PMCID: PMC3693557  PMID: 19170108
BRCA1/1a/1b proteins; breast cancers; mitochondria; growth suppression; transcriptional regulation; ELK-1
10.  EMSY overexpression disrupts the BRCA2/RAD51 pathway in the DNA-damage response: implications for chromosomal instability/recombination syndromes as checkpoint diseases 
Molecular Genetics and Genomics  2011;285(4):325-340.
EMSY links the BRCA2 pathway to sporadic breast/ovarian cancer. It encodes a nuclear protein that binds to the BRCA2 N-terminal domain implicated in chromatin/transcription regulation, but when sporadically amplified/overexpressed, increased EMSY level represses BRCA2 transactivation potential and induces chromosomal instability, mimicking the activity of BRCA2 mutations in the development of hereditary breast/ovarian cancer. In addition to chromatin/transcription regulation, EMSY may also play a role in the DNA-damage response, suggested by its ability to localize at chromatin sites of DNA damage/repair. This implies that EMSY overexpression may also repress BRCA2 in DNA-damage replication/checkpoint and recombination/repair, coordinated processes that also require its interacting proteins: PALB2, the partner and localizer of BRCA2; RPA, replication/checkpoint protein A; and RAD51, the inseparable recombination/repair enzyme. Here, using a well-characterized recombination/repair assay system, we demonstrate that a slight increase in EMSY level can indeed repress these two processes independently of transcriptional interference/repression. Since EMSY, RPA and PALB2 all bind to the same BRCA2 region, these findings further support a scenario wherein: (a) EMSY amplification may mimic BRCA2 deficiency, at least by overriding RPA and PALB2, crippling the BRCA2/RAD51 complex at DNA-damage and replication/transcription sites; and (b) BRCA2/RAD51 may coordinate these processes by employing at least EMSY, PALB2 and RPA. We extensively discuss the molecular details of how this can happen to ascertain its implications for a novel recombination mechanism apparently conceived as checkpoint rather than a DNA repair system for cell division, survival, death, and human diseases, including the tissue specificity of cancer predisposition, which may renew our thinking about targeted therapy and prevention.
PMCID: PMC3064890  PMID: 21409565
Tumor-suppressor genes; Oncogenes; Development/abortion; Aging; Estrogens
11.  Prevalence of the variant allele rs61764370 T>G in the 3′UTR of KRAS among Dutch BRCA1, BRCA2 and non-BRCA1/BRCA2 breast cancer families 
Recently, a variant allele in the 3′UTR of the KRAS gene (rs61764370 T>G) was shown to be associated with an increased risk for developing non-small cell lung cancer, as well as ovarian cancer, and was most enriched in ovarian cancer patients from hereditary breast and ovarian cancer families. This functional variant has been shown to disrupt a let-7 miRNA binding site leading to increased expression of KRAS in vitro. In the current study, we have genotyped this KRAS-variant in breast cancer index cases from 268 BRCA1 families, 89 BRCA2 families, 685 non-BRCA1/BRCA2 families, and 797 geographically matched controls. The allele frequency of the KRAS-variant was found to be increased among patients with breast cancer from BRCA1, but not BRCA2 or non-BRCA1/BRCA2 families as compared to controls. As BRCA1 carriers mostly develop ER-negative breast cancers, we also examined the variant allele frequency among indexes from non-BRCA1/BRCA2 families with ER-negative breast cancer. The prevalence of the KRAS-variant was, however, not significantly increased as compared to controls, suggesting that the variant allele not just simply associates with ER-negative breast cancer. Subsequent expansion of the number of BRCA1 carriers with breast cancer by including other family members in addition to the index cases resulted in loss of significance for the association between the variant allele and mutant BRCA1 breast cancer. In this same cohort, the KRAS-variant did not appear to modify breast cancer risk for BRCA1 carriers. Importantly, results from the current study suggest that KRAS-variant frequencies might be increased among BRCA1 carriers, but solid proof requires confirmation in a larger cohort of BRCA1 carriers.
PMCID: PMC3735357  PMID: 20676756
KRAS-variant; Let-7; Breast cancer susceptibility; Association; BRCA1
12.  The Epistatic Relationship between BRCA2 and the Other RAD51 Mediators in Homologous Recombination 
PLoS Genetics  2011;7(7):e1002148.
RAD51 recombinase polymerizes at the site of double-strand breaks (DSBs) where it performs DSB repair. The loss of RAD51 causes extensive chromosomal breaks, leading to apoptosis. The polymerization of RAD51 is regulated by a number of RAD51 mediators, such as BRCA1, BRCA2, RAD52, SFR1, SWS1, and the five RAD51 paralogs, including XRCC3. We here show that brca2-null mutant cells were able to proliferate, indicating that RAD51 can perform DSB repair in the absence of BRCA2. We disrupted the BRCA1, RAD52, SFR1, SWS1, and XRCC3 genes in the brca2-null cells. All the resulting double-mutant cells displayed a phenotype that was very similar to that of the brca2-null cells. We suggest that BRCA2 might thus serve as a platform to recruit various RAD51 mediators at the appropriate position at the DNA–damage site.
Author Summary
Mutations in BRCA1 and BRCA2 predispose hereditary breast and ovarian cancer. Such mutations sensitize to chemotherapeutic agents, including camptothecin, cisplatin, and poly(ADP-ribose) polymerase (PARP) inhibitor, since RAD51 mediators including both BRCA proteins promote repair of DNA lesions induced by these drugs. Little is known of the functional relationships among RAD51, BRCA2, and other RAD51 mediators, because no brca2-null cells were available. Furthermore, the phenotype of sws1 mutants has not been documented. We here disrupted every known RAD51 mediator and analyzed the phenotype of the resulting mutants in both BRCA2-deficient and -proficient backgrounds. The understanding of the function of individual RAD51 mediators and their functional interactions will contribute to the accurate prediction of anti-cancer therapy efficacy.
PMCID: PMC3136442  PMID: 21779174
13.  BRCA1 Expression is an Important Biomarker for Chemosensitivity: Suppression of BRCA1 Increases the Apoptosis via Up-regulation of p53 and p21 During Cisplatin Treatment in Ovarian Cancer Cells 
Biomarker Insights  2007;1:49-59.
BRCA1 is a tumor suppressor which plays a crucial role in the repair of DNA double-strand breaks, and its abnormality is responsible for hereditary ovarian cancer syndrome. It has recently been reported that reduced expression of BRCA1 is also common in sporadic ovarian carcinoma via its promoter hypermethylation, and that ovarian carcinoma patients negative for BRCA1 expression showed favorable prognosis. To address if BRCA1 expression plays a role in the chemotherapeutic response, we analyzed the effect of BRCA1 suppression on the sensitivity to cisplatin and paclitaxel in ovarian cancer cells. Specific siRNA for BRCA1 gene was transfected into 3 ovarian cancer cell lines with various p53 status. Reduced expression of BRCA1 by transfection of BRCA1-siRNA resulted in a 5.3-fold increase in sensitivity to cisplatin in p53-wild A2780 cells, but not in p53-mutated A2780/CDDP and p53-deleted SKOV3 cells. Regarding the sensitivity to paclitaxel, BRCA1 suppression caused no significant changes in all the 3 cell lines. For ionizing radiation sensitivity, BRCA1 suppression also showed a significant higher sensitivity in A2780 cells. Growth curve and cell cycle analyses showed no significant differences between BRCA1-siRNA-transfected A2780 cells and control cells. However, cisplatin treatment under suppression of BRCA1 showed a significantly increased apoptosis along with up-regulation of p53 and p21 in A2780 cells. Accordingly, reduced expression of BRCA1 enhances the cisplatin sensitivity and apoptosis via up-regulation of p53 and p21, but does not affect the paclitaxel sensitivity. Expression of BRCA1 might be an important biomarker for cisplatin resistance in ovarian carcinoma.
PMCID: PMC2716781  PMID: 19690636
BRCA1; ovarian cancer; biomarker; chemosensitivity; cisplatin
14.  The Preclinical Natural History of Serous Ovarian Cancer: Defining the Target for Early Detection 
PLoS Medicine  2009;6(7):e1000114.
Pat Brown and colleagues carry out a modeling study and define what properties a biomarker-based screening test would require in order to be clinically useful.
Ovarian cancer kills approximately 15,000 women in the United States every year, and more than 140,000 women worldwide. Most deaths from ovarian cancer are caused by tumors of the serous histological type, which are rarely diagnosed before the cancer has spread. Rational design of a potentially life-saving early detection and intervention strategy requires understanding the lesions we must detect in order to prevent lethal progression. Little is known about the natural history of lethal serous ovarian cancers before they become clinically apparent. We can learn about this occult period by studying the unsuspected serous cancers that are discovered in a small fraction of apparently healthy women who undergo prophylactic bilateral salpingo-oophorectomy (PBSO).
Methods and Findings
We developed models for the growth, progression, and detection of occult serous cancers on the basis of a comprehensive analysis of published data on serous cancers discovered by PBSO in BRCA1 mutation carriers. Our analysis yielded several critical insights into the early natural history of serous ovarian cancer. First, these cancers spend on average more than 4 y as in situ, stage I, or stage II cancers and approximately 1 y as stage III or IV cancers before they become clinically apparent. Second, for most of the occult period, serous cancers are less than 1 cm in diameter, and not visible on gross examination of the ovaries and Fallopian tubes. Third, the median diameter of a serous ovarian cancer when it progresses to an advanced stage (stage III or IV) is about 3 cm. Fourth, to achieve 50% sensitivity in detecting tumors before they advance to stage III, an annual screen would need to detect tumors of 1.3 cm in diameter; 80% detection sensitivity would require detecting tumors less than 0.4 cm in diameter. Fifth, to achieve a 50% reduction in serous ovarian cancer mortality with an annual screen, a test would need to detect tumors of 0.5 cm in diameter.
Our analysis has formalized essential conditions for successful early detection of serous ovarian cancer. Although the window of opportunity for early detection of these cancers lasts for several years, developing a test sufficiently sensitive and specific to take advantage of that opportunity will be a challenge. We estimated that the tumors we would need to detect to achieve even 50% sensitivity are more than 200 times smaller than the clinically apparent serous cancers typically used to evaluate performance of candidate biomarkers; none of the biomarker assays reported to date comes close to the required level of performance. Overcoming the signal-to-noise problem inherent in detection of tiny tumors will likely require discovery of truly cancer-specific biomarkers or development of novel approaches beyond traditional blood protein biomarkers. While this study was limited to ovarian cancers of serous histological type and to those arising in BRCA1 mutation carriers specifically, we believe that the results are relevant to other hereditary serous cancers and to sporadic ovarian cancers. A similar approach could be applied to other cancers to aid in defining their early natural history and to guide rational design of an early detection strategy.
Please see later in the article for Editors' Summary
Editors' Summary
Every year about 190,000 women develop ovarian cancer and more than 140,000 die from the disease. Ovarian cancer occurs when a cell on the surface of the ovaries (two small organs in the pelvis that produce eggs) or in the Fallopian tubes (which connect the ovaries to the womb) acquires genetic changes (mutations) that allow it to grow uncontrollably and to spread around the body (metastasize). For women whose cancer is diagnosed when it is confined to the site of origin—ovary or Fallopian tube—(stage I disease), the outlook is good; 70%–80% of these women survive for at least 5 y. However, very few ovarian cancers are diagnosed this early. Usually, by the time the cancer causes symptoms (often only vague abdominal pain and mild digestive disturbances), it has spread into the pelvis (stage II disease), into the space around the gut, stomach, and liver (stage III disease), or to distant organs (stage IV disease). Patients with advanced-stage ovarian cancer are treated with surgery and chemotherapy but, despite recent treatment improvements, only 15% of women diagnosed with stage IV disease survive for 5 y.
Why Was This Study Done?
Most deaths from ovarian cancer are caused by serous ovarian cancer, a tumor subtype that is rarely diagnosed before it has spread. Early detection of serous ovarian cancer would save the lives of many women but no one knows what these cancers look like before they spread or how long they grow before they become clinically apparent. Learning about this occult (hidden) period of ovarian cancer development by observing tumors from their birth to late-stage disease is not feasible. However, some aspects of the early natural history of ovarian cancer can be studied by using data collected from healthy women who have had their ovaries and Fallopian tubes removed (prophylactic bilateral salpingo-oophorectomy [PBSO]) because they have inherited a mutated version of the BRCA1 gene that increases their ovarian cancer risk. In a few of these women, unsuspected ovarian cancer is discovered during PBSO. In this study, the researchers identify and analyze the available reports on occult serous ovarian cancer found this way and then develop mathematical models describing the early natural history of ovarian cancer.
What Did the Researchers Do and Find?
The researchers first estimated the time period during which the detection of occult tumors might save lives using the data from these reports. Serous ovarian cancers, they estimated, spend more than 4 y as in situ (a very early stage of cancer development), stage I, or stage II cancers and about 1 y as stage III and IV cancers before they become clinically apparent. Next, the researchers used the data to develop mathematical models for the growth, progression, and diagnosis of serous ovarian cancer (the accuracy of which depends on the assumptions used to build the models and on the quality of the data fed into them). These models indicated that, for most of the occult period, serous cancers had a diameter of less than 1 cm (too small to be detected during surgery or by gross examination of the ovaries or Fallopian tubes) and that more than half of serous cancers had advanced to stage III/IV by the time they measured 3 cm across. Furthermore, to enable the detection of half of serous ovarian cancers before they reached stage III, an annual screening test would need to detect cancers with a diameter of 1.3 cm and to halve deaths from serous ovarian cancer, an annual screening test would need to detect 0.5-cm diameter tumors.
What Do These Findings Mean?
These findings suggest that the time period over which the early detection of serous ovarian cancer would save lives is surprisingly long. More soberingly, the authors find that a test that is sensitive and specific enough to take advantage of this “window of opportunity” would need to detect tumors hundreds of times smaller than clinically apparent serous cancers. So far no ovarian cancer-specific protein or other biomarker has been identified that could be used to develop a test that comes anywhere near this level of performance. Identification of truly ovarian cancer-specific biomarkers or novel strategies will be needed in order to take advantage of the window of opportunity. The stages prior to clinical presentation of other lethal cancers are still very poorly understood. Similar studies of the early natural history of these cancers could help guide the development of rational early detection strategies.
Additional Information
Please access these Web sites via the online version of this summary at
The US National Cancer Institute provides a brief description of what cancer is and how it develops and information on all aspects of ovarian cancer for patients and professionals. It also provides a fact sheet on BRCA1 mutations and cancer risk (in English and Spanish)
The UK charity Cancerbackup also provides information about all aspects of ovarian cancer
MedlinePlus provides a list of links to additional information about ovarian cancer (in English and Spanish)
The Canary Foundation is a nonprofit organization dedicated to development of effective strategies for early detection of cancers including ovarian cancer.
PMCID: PMC2711307  PMID: 19636370
15.  Accumulation of p53 protein is frequent in ovarian cancers associated with BRCA1 and BRCA2 germline mutations. 
Journal of Clinical Pathology  1999;52(5):372-375.
BACKGROUND: Mutations in the BRCA1 or BRCA2 genes are responsible for up to 95% of hereditary ovarian cancer cases. Both genes function as tumour suppressor genes, and development of a cancer is thought to require an accumulation of somatic genetic events in addition to the inherited germline predisposition. It is unknown whether these somatic events in BRCA associated ovarian cancer are similar to or distinct from those in sporadic cases. The most frequent somatic genetic event in ovarian cancer is a mutation of the p53 gene. AIM: To study the role of p53 in hereditary ovarian cancer, by analysing accumulation of the p53 protein in ovarian cancers which occurred in BRCA1 or BRCA2 germline mutation carriers and comparing the results with a panel of ovarian cancers from patients who tested negative for both BRCA1 and BRCA2. METHODS: The study group consisted of 39 ovarian cancer patients in whom a BRCA mutation had been confirmed previously. p53 Immunohistochemistry was performed on archival tissue using a standard microwave antigen retrieval technique. The rate of p53 accumulation was compared with 40 ovarian cancer cases who tested negative for BRCA1 and BRCA2 germline mutations. RESULTS: P53 Accumulation was similar in BRCA related ovarian cancers and BRCA negative controls. Overall 27 of 39 BRCA1 or BRCA2 positive cases (69%) had evidence of p53 accumulation, compared with 24 of 40 invasive ovarian cancer cases (60%) which tested negative for BRCA1 and BRCA2 germline mutations. BRCA1 related ovarian cancers showed p53 accumulation in 22 of 30 cases (73%); p53 accumulation was present in five of nine BRCA2 related ovarian cancers. CONCLUSIONS: In addition to germline BRCA1 and BRCA2 mutations, somatic p53 alterations leading to p53 accumulation are an important event in hereditary ovarian cancer and are as frequent as in non-BRCA-related ovarian cancer.
PMCID: PMC1023075  PMID: 10560359
16.  Methylation and protein expression of DNA repair genes: association with chemotherapy exposure and survival in sporadic ovarian and peritoneal carcinomas 
Molecular Cancer  2009;8:48.
DNA repair genes critically regulate the cellular response to chemotherapy and epigenetic regulation of these genes may be influenced by chemotherapy exposure. Restoration of BRCA1 and BRCA2 mediates resistance to platinum chemotherapy in recurrent BRCA1 and BRCA2 mutated hereditary ovarian carcinomas. We evaluated BRCA1, BRCA2, and MLH1 protein expression in 115 sporadic primary ovarian carcinomas, of which 31 had paired recurrent neoplasms collected after chemotherapy. Additionally, we assessed whether promoter methylation of BRCA1, MLH1 or FANCF influenced response to chemotherapy or explained alterations in protein expression after chemotherapy exposure.
Of 115 primary sporadic ovarian carcinomas, 39 (34%) had low BRCA1 protein and 49 (42%) had low BRCA2 expression. BRCA1 and BRCA2 protein expression were highly concordant (p < 0.0001). MLH1 protein loss occurred in 28/115 (24%) primary neoplasms. BRCA1 protein loss in primary neoplasms was associated with better survival (p = 0.02 Log Rank test) and remained significant after accounting for either stage or age in a multivariate model (p = 0.04, Cox proportional hazards). In paired specimens, BRCA1 protein expression increased in 13/21 (62%) and BRCA2 protein expression increased in 15/21 (71%) of recurrent carcinomas with low or intermediate protein in the paired primary. In contrast MLH1 expression was rarely decreased in recurrent carcinomas (1/33, 3%). Similar frequencies of MLH1, BRCA1, and FANCF promoter methylation occurred in primary carcinomas without previous chemotherapy, after neoadjuvant chemotherapy, or in recurrent neoplasms.
Low BRCA1 expression in primary sporadic ovarian carcinoma is associated with prolonged survival. Recurrent ovarian carcinomas commonly have increased BRCA1 and/or BRCA2 protein expression post chemotherapy exposure which could mediate resistance to platinum based therapies. However, alterations in expression of these proteins after chemotherapy are not commonly mediated by promoter methylation, and other regulatory mechanisms are likely to contribute to these alterations.
PMCID: PMC2719582  PMID: 19602291
17.  BRCA1 represses Amphiregulin gene expression 
Cancer research  2010;70(3):996-1005.
BRCA1, the breast and ovarian cancer specific tumor suppressor, is a transcriptional repressor as well as a transcriptional activator dependent on the promoter context. In order to identify the genes activated or repressed by BRCA1, we have analyzed microarray results from cells depleted of BRCA1 and revealed a number of genes regulated by BRCA1 on the level of transcription. Among the genes repressed by BRCA1 we have identified Amphiregulin (AREG) and Early Growth Response-1 (EGR1). Results indicate that BRCA1 regulates AREG transcription directly through the binding to the AREG promoter, however we could not detect BRCA1 on the EGR1 promoter, suggesting that EGR1 is indirectly regulated by BRCA1. In an attempt to indentify the mechanism of the AREG transcriptional repression by BRCA1, we have mapped two independent BRCA1-response elements on the AREG promoter located at the positions −202/−182 and +19/+122. BRCA1 depletion leads to induction of AREG protein. Taken together, our data builds the connection between BRCA1 loss of function and AREG up-regulation, a change in gene expression often observed in breast cancer.
PMCID: PMC2816672  PMID: 20103632
BRCA1; Amphiregulin (AREG); transcription regulation; breast cancer
18.  BRCA1 Interacts with Smad3 and Regulates Smad3-Mediated TGF-β Signaling during Oxidative Stress Responses 
PLoS ONE  2009;4(9):e7091.
BRCA1 is a key regulatory protein participating in cell cycle checkpoint and DNA damage repair networks. BRCA1 plays important roles in protecting numerous cellular processes in response to cell damaging signals. Transforming growth factor-beta (TGF-β) is a potent regulator of growth, apoptosis and invasiveness of tumor cells. TFG-β activates Smad signaling via its two cell surface receptors, the TbetaRII and ALK5/TbetaRI, leading to Smad-mediated transcriptional regulation.
Methodology/Principal Findings
Here, we report an important role of BRCA1 in modulating TGF-β signaling during oxidative stress responses. Wild-type (WT) BRCA1, but not mutated BRCA1 failed to activate TGF-β mediated transactivation of the TGF-β responsive reporter, p3TP-Lux. Further, WT-BRCA1, but not mutated BRCA1 increased the expression of Smad3 protein in a dose-dependent manner, while silencing of WT-BRCA1 by siRNA decreased Smad3 and Smad4 interaction induced by TGF-β in MCF-7 breast cancer cells. BRCA1 interacted with Smad3 upon TGF-β1 stimulation in MCF-7 cells and this interaction was mediated via the domain of 298–436aa of BRCA1 and Smad3 domain of 207–426aa. In addition, H2O2 increased the colocalization and the interaction of Smad3 with WT-BRCA1. Interestingly, TGF-β1 induced Smad3 and Smad4 interaction was increased in the presence of H2O2 in cells expressing WT-BRCA1, while the TGF-β1 induced interaction between Smad3 and Smad4 was decreased upon H2O2 treatment in a dose-dependent manner in HCC1937 breast cancer cells, deficient for endogenous BRCA1. This interaction between Smad3 and Smad4 was increased in reconstituted HCC1937 cells expressing WT-BRCA1 (HCC1937/BRCA1). Further, loss of BRCA1 resulted in H2O2 induced nuclear export of phosphor-Smad3 protein to the cytoplasm, resulting decreased of Smad3 and Smad4 interaction induced by TGF-β and in significant decrease in Smad3 and Smad4 transcriptional activities.
These results strongly suggest that loss or reduction of BRCA1 alters TGF-β growth inhibiting activity via Smad3 during oxidative stress responses.
PMCID: PMC2740868  PMID: 19768112
19.  BRCA1 and BRCA2 Unclassified Variants and Missense Polymorphisms in Algerian Breast/Ovarian Cancer Families 
Disease markers  2012;32(6):343-353.
Background: BRCA1 and BRCA2 germline mutations predispose heterozygous carriers to hereditary breast/ovarian cancer. However, unclassified variants (UVs) (variants with unknown clinical significance) and missense polymorphisms in BRCA1 and BRCA2 genes pose a problem in genetic counseling, as their impact on risk of breast and ovarian cancer is still unclear. The objective of our study was to identify UVs and missense polymorphisms in Algerian breast/ovarian cancer patients and relatives tested previously for BRCA1 and BRCA2 genes germline mutations analysis.
Methods: We analyzed 101 DNA samples from 79 breast/ovarian cancer families. The approach used is based on BRCA1 and BRCA2 sequence variants screening by SSCP or High-Resolution Melting (HRM) curve analysis followed by direct sequencing. In silico analyses have been performed using different bioinformatics programs to individualize genetics variations that can disrupt the BRCA1 and BRCA2 genes function.
Results: Among 80 UVs and polymorphisms detected in BRCA1/2 genes (33 BRCA2 and 47 BRCA2), 31 were new UVs (10 BRCA2 and 21 BRCA2), 7 were rare UVs (4 BRCA2 and 3 BRCA2) and 42 were polymorphic variants (19 BRCA2 and 23 BRCA2). Moreover, 8 new missense UVs identified in this study: two BRCA1 (c.4066C>A/p.Gln1356Lys, c.4901G>T/p.Arg1634Met) located respectively in exons 11 and 16, and six BRCA2 (c.1099G>A/p.Asp367Asn, c.2636C>A/p.Ser879Tyr, c.3868T>A/p.Cys1290Ser, c.5428G>T/p.Val1810Phe, c.6346C>G/p.His2116Asp and c.9256G>A/p.Gly3086Arg) located respectively in exons 10, 11 and 24, show a damaging PSIC score yielded by PolyPhen2 program and could be pathogenic. In addition, 5 new BRCA2 missense UVs out of six that were found to be damaging by PolyPhen2 program, also were deleterious according to SIFT program. The rare BRCA2 UV c.5332G>A/p.Asp1778Asn was found here for the first time in co-occurrence in trans with the deleterious BRCA1 mutation c.798_799delTT/p.Ser267LysfsX19 in young breast cancer patient. Moreover, 10 new identified intronic variants with unknown clinical significance (3 BRCA1 and 7 BRCA2) in the present study, could be considered as benign, because GeneSplicer, SpliceSiteFinder and MaxEntScan prediction programs show no splice site alteration for these variants. Several missense polymorphisms of BRCA1 c.2612C>T/p.Pro871Leu, c.3548A>G/p.Lys1183Arg, c.4837A>G/p.Ser1613Gly and BRCA2 c.865A>C/p.Asn289His, c.1114A>C/p.Asn372His, c.2971A>G/p.Asn991Asp, c.7150C>A/p.Gly2384Lys have been identified with high frequency in patients who were tested negative for BRCA1 and BRCA2 mutations. These missense polymorphisms could have a role as susceptibility breast cancer markers in Algerian breast/ovarian cancer families where pathological BRCA1 and BRCA2 mutations were not present.
Conclusions: For the first time, UVs and missense polymorphisms in BRCA1 and BRCA2 genes have been identified in Algerian breast/ovarian cancer families. Evaluation of breast/ovarian cancer risk induced by the eight new missense UVs and common polymorphisms detected in our present work is on going in a larger study.
PMCID: PMC3826381  PMID: 22684231
Algeria; BRCA1; BRCA2; breast/ovarian cancer; HRM; polymorphisms; SNP; UVs
20.  Roles of brca2 (fancd1) in Oocyte Nuclear Architecture, Gametogenesis, Gonad Tumors, and Genome Stability in Zebrafish 
PLoS Genetics  2011;7(3):e1001357.
Mild mutations in BRCA2 (FANCD1) cause Fanconi anemia (FA) when homozygous, while severe mutations cause common cancers including breast, ovarian, and prostate cancers when heterozygous. Here we report a zebrafish brca2 insertional mutant that shares phenotypes with human patients and identifies a novel brca2 function in oogenesis. Experiments showed that mutant embryos and mutant cells in culture experienced genome instability, as do cells in FA patients. In wild-type zebrafish, meiotic cells expressed brca2; and, unexpectedly, transcripts in oocytes localized asymmetrically to the animal pole. In juvenile brca2 mutants, oocytes failed to progress through meiosis, leading to female-to-male sex reversal. Adult mutants became sterile males due to the meiotic arrest of spermatocytes, which then died by apoptosis, followed by neoplastic proliferation of gonad somatic cells that was similar to neoplasia observed in ageing dead end (dnd)-knockdown males, which lack germ cells. The construction of animals doubly mutant for brca2 and the apoptotic gene tp53 (p53) rescued brca2-dependent sex reversal. Double mutants developed oocytes and became sterile females that produced only aberrant embryos and showed elevated risk for invasive ovarian tumors. Oocytes in double-mutant females showed normal localization of brca2 and pou5f1 transcripts to the animal pole and vasa transcripts to the vegetal pole, but had a polarized rather than symmetrical nucleus with the distribution of nucleoli and chromosomes to opposite nuclear poles; this result revealed a novel role for Brca2 in establishing or maintaining oocyte nuclear architecture. Mutating tp53 did not rescue the infertility phenotype in brca2 mutant males, suggesting that brca2 plays an essential role in zebrafish spermatogenesis. Overall, this work verified zebrafish as a model for the role of Brca2 in human disease and uncovered a novel function of Brca2 in vertebrate oocyte nuclear architecture.
Author Summary
Women with one strong BRCA2(FANCD1) mutation have high risks of breast and ovarian cancer. People with two mild BRCA2(FANCD1) mutations develop Fanconi Anemia, which reduces DNA repair leading to genome instability, small gonads, infertility, and cancer. Humans and mice lacking BRCA2 activity die before birth. We discovered that zebrafish brca2 mutants show chromosome instability and small gonads, and they develop only as sterile adult males. Female-to-male sex reversal is due to oocyte death during sex determination. Normal animals expressed brca2 in developing eggs and sperm that are repairing DNA breaks associated with genetic reshuffling. Normal developing eggs localized brca2 RNA near the nucleus, suggesting a role in protecting rapidly dividing early embryonic cells. Sperm-forming cells died in adult mutant males. Inhibition of cell death rescued sex reversal, but not fertility. Rescued females developed invasive ovarian tumors and formed eggs with abnormal nuclear architecture. The novel role of Brca2 in organizing the vertebrate egg nucleus may provide new insights into the origin of ovarian cancer. These results validate zebrafish as a model for human BRCA2-related diseases and provide a tool for the identification of substances that can rescue zebrafish brca2 mutants and thus become candidates for therapeutic molecules for human disease.
PMCID: PMC3069109  PMID: 21483806
21.  DNA damage-induced cytotoxicity is dissociated from BRCA1’s DNA repair function but dependent on its cytosolic accumulation 
Cancer research  2010;70(15):6258-6267.
The tumor suppressor BRCA1 is a nuclear shuttling protein. However, the role of BRCA1 localization in the control of its functions remains to be elucidated. Given the central role of BRCA1 in DNA damage repair, we hypothesized that depletion of nuclear BRCA1 will compromise its nuclear function in DNA repair and thereby result in enhanced cytotoxic response to DNA damage. In this study, we showed that repair of DNA double strand breaks (DSBs) required BRCA1 in the nucleus. In addition, sequestering BRCA1 in the cytosol enhanced the cytotoxic response to ionizing radiation (IR) or cisplatin in human breast and colon cancer cells. However, further genetic dissection of the mechanism of this enhanced cytotoxicity using BRCA1 mutants deficient in DSB repair unexpectedly revealed a dissociation of BRCA1’s function in DNA repair from its effects on cellular sensitivity to DNA damage. Interestingly, we observed a dependence of the DNA damage-induced cell killing on the translocation and accumulation of BRCA1 in the cytosol. Together, these data suggest a novel role of cytoplasmic translocation of BRCA1, not only in controlling its DNA repair functions, but also in the regulation of cell death processes following DNA damage. Further dissection of the mechanism of cytotoxicity induced by BRCA1 cytoplasmic translocation revealed involvement of the apoptotic pathway. We propose that the status of BRCA1 nuclear/cytoplasmic shuttling may provide a molecular marker to predict tumor response and a potential novel target to sensitize cancer cells to DNA damage-based therapy.
PMCID: PMC2912952  PMID: 20631074
BRCA1; nuclear export; apoptosis; DNA repair; homologous recombination; radiation sensitization; checkpoint
Molecular oncology  2013;7(3):567-579.
Mutations in BRCA1/2 increase the risk of developing breast and ovarian cancer. Germline BRCA1/2 mutations occur in 8.6-13.7% of unselected epithelial ovarian cancers, somatic mutations are also frequent. BRCA1/2 mutated or dysfunctional cells may be sensitive to PARP inhibition by synthetic lethality. The aim of this study is to comprehensively characterise the BRCA1/2 status of a large panel of ovarian cancer cell lines available to the research community to assist in biomarker studies of novel drugs and in particular of PARP inhibitors.
The BRCA1/2 genes were sequenced in 41 ovarian cell lines, mRNA expression of BRCA1/2 and gene methylation status of BRCA1 was also examined. The cytotoxicity of PARP inhibitors olaparib and veliparib was examined in 20 cell lines.
The cell line SNU-251 has a deleterious BRCA1 mutation at 5564G>A, and is the only deleterious BRCA1/2 mutant in the panel. Two cell lines (UPN-251 and PEO1) had deleterious mutations as well as additional reversion mutations that restored the protein functionality. Heterozygous mutations in BRCA1/2 were relatively common, found in 14.6% of cell lines. BRCA1 was methylated in two cell lines (OVCAR8, A1847) and there was a corresponding decrease in gene expression. The BRCA1 methylated cell lines were more sensitive to PARP inhibition than wild-type cells. The SNU-251 deleterious mutant was more sensitive to PARP inhibition, but only in a long-term exposure to correct for its slow growth rate. Cell lines derived from metastatic disease are significantly more resistant to veliparib (2.0 fold p = 0.03) compared to those derived from primary tumours. Resistance to olaparib and veliparib was correlated Pearsons-R 0.5393, p = 0.0311.
The incidence of BRCA1/2 deleterious mutations 1/41 cell lines derived from 33 different patients (3.0%) is much lower than the population incidence. The reversion mutations and high frequency of heterozygous mutations suggest that there is a selective pressure against BRCA1/2 in cell culture similar to the selective pressure seen in the clinic after treatment with chemotherapy. PARP inhibitors may be useful in patients with BRCA1 deleterious mutations or gene methylation.
PMCID: PMC4106023  PMID: 23415752
BRCA1/2; ovarian; mutation; methylation; parp inhibitor; olaparib; veliparib
23.  Extracellular Matrix Enhances Heregulin-Dependent BRCA1 Phosphorylation and Suppresses BRCA1 Expression through Its C Terminus 
Molecular and Cellular Biology  2003;23(2):579-593.
Germ line mutations in the breast cancer susceptibility gene BRCA1 account for the increased risk of early onset of familial breast cancer, whereas overexpression of the ErbB family of receptor tyrosine kinases has been linked to the development of nonfamilial or sporadic breast cancer. To analyze whether there is a link between these two regulatory molecules, we studied the effects of ErbB-2 activation by heregulin (HRG) on BRCA1 function. It was previously demonstrated that HRG induced the phosphorylation of BRCA1, which was mediated by the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Since altered interaction between cells and the surrounding extracellular matrix (ECM) is a common feature in a variety of tumors and since ECM modulates intracellular signaling, we hypothesized that ECM may affect the expression and HRG-dependent phosphorylation of BRCA1. Following stimulation by HRG, a strong increase in [3H]thymidine incorporation was observed in human T47D breast cancer cells seeded on plastic (PL). When T47D cells were seeded on laminin (LAM) or Matrigel, HRG induced a significantly higher proliferation than it did in cells seeded on PL. T47D cells seeded on poly-l-lysine had an abrogated mitogenic response, indicating the involvement of integrins in this process. HRG treatment induced a transient phosphorylation of BRCA1 that was enhanced in T47D cells grown on LAM. LAM-enhanced BRCA1 phosphorylation was mediated through α6 integrin upon HRG stimulation. Accordingly, T47D cells grown on LAM had the greatest increase in ErbB-2 activation, PI3K activity, and phosphorylation of Akt. A similar pattern of BRCA1 mRNA expression was observed when T47D cells were seeded on PL, LAM, or COL4. There was a significant decrease in the steady state of the BRCA1 mRNA level on both the LAM and COL4 matrices compared to that for cells seeded on PL. In addition, HRG stimulation caused a significant decrease in BRCA1 mRNA expression that was dependent on protein synthesis. Pretreatment with both the calpain inhibitor ALLN (N-acetyl-Leu-Leu-norleucinal) and the proteosome inhibitor lactacystin inhibited the HRG-induced down-regulation of BRCA1 mRNA expression. Likewise, there was a strong decrease in the protein level of BRCA1 in T47D cells 4 h after treatment with HRG compared to its level in control nontreated T47D cells. Pretreatment with the proteosome inhibitors ALLN, lactacystin, and PSI [N-benzyloxycarbonyl-Ile-Glu-(O-t-butyl)-Ala-leucinal] inhibited also the HRG-induced down-regulation of BRCA1 protein in breast cancer cells. Interestingly, BRCA1 mRNA expression in HCC-1937 breast cancer cells, which express C-terminally truncated BRCA1, was not affected by either LAM or CL4. No phosphorylation of BRCA1 from HCC-1937 cells was observed in response to HRG. While Cdk4 phosphorylated wild-type BRCA1 in response to HRG in T47D cells, Cdk4 failed to phosphorylate the truncated form of BRCA1 in HCC-1937 cells. Furthermore, overexpression of wild-type BRCA1 in HCC-1937 cells resulted in the phosphorylation of BRCA1 and decreased BRCA1 expression upon HRG stimulation while overexpression of truncated BRCA1 in T47D cells resulted in a lack of BRCA1 phosphorylation and restoration of BRCA1 expression. These findings suggest that ECM enhances HRG-dependent BRCA1 phosphorylation and that ECM and HRG down-regulate BRCA1 expression in breast cancer cells. Furthermore, ECM suppresses BRCA1 expression through the C terminus of BRCA1.
PMCID: PMC151527  PMID: 12509456
24.  BRCA1 Expression Is Epigenetically Repressed in Sporadic Ovarian Cancer Cells by Overexpression of C-Terminal Binding Protein 212 
Neoplasia (New York, N.Y.)  2013;15(6):600-608.
Ovarian cancer is the leading cause of mortality from gynecological malignancy despite advancements in novel therapeutics. We have recently demonstrated that the transcriptional co-repressor C-terminal binding protein 2 (CtBP2) is overexpressed in epithelial ovarian carcinoma.
Materials and Methods
Reverse-transcribed cDNA from CtBP2 wild-type and knockdown ovarian cancer cell lines was hybridized to Affymetrix Gene 1.0 ST microarrays, and differentially expressed genes were studied. Immunohistochemical analysis of CtBP2 and BRCA1 staining of ovarian tissues was performed. Chromatin immunoprecipitation (ChIP) and luciferase assays were carried out. The effect of the drugs 4-methylthio-2-oxobutyric acid (MTOB) and poly(ADP-ribose) polymerase (PARP) inhibitor Olaparib on CtBP2 wild-type and knockdown cell lines was examined using methylthiazol tetrazolium assays and an xCELLigence System.
Eighty-five genes involved in DNA repair, mitotic checkpoint, nucleosome assembly, and the BRCA1 network were differentially regulated by CtBP2 expression. ChIP and luciferase reporter assays using a BRCA1 promoter-regulated luciferase construct indicated that the CtBP2 complex binds the BRCA1 promoter and represses BRCA1 transcription. Immunohistochemistry illustrated a significant inverse CtBP2 and BRCA1 expression in a panel of malignant ovarian tumor tissues. The CtBP2 inhibitor MTOB suppressed ovarian cancer cell survival in a CtBP2-dependent manner. Ovarian cancer cells with CtBP2 knockdown did not display increased sensitivity to the PARP inhibitor Olaparib.
CtBP2 is an ovarian cancer oncogene that may play a significant role in epigenetically silencing BRCA1 function in sporadic epithelial ovarian cancer. CtBP2-specific inhibitors, such as MTOB, may be effective adjunct therapies in the management of patients with CtBP2-positive ovarian carcinoma.
PMCID: PMC3664992  PMID: 23730208
25.  BRCA1 regulates insulin-like growth factor 1 receptor levels in ovarian cancer 
Oncology Letters  2014;7(5):1733-1737.
Breast cancer 1 (BRCA1) and insulin-like growth factor 1 receptor (IGF1R) are critical in ovarian cancer progression. However, the crosstalk between the BRCA1 and IGF1R signaling pathways in ovarian cancer remains largely unknown. The effects of BRCA1 on IGF1R were assessed in 121 serous ovarian cancer patients (BRCA1 mutation, n=30; non-BRCA1 mutation, n=32; hypermethylated BRCA1 promoter, n=28; and non-methylation, n=31). BRCA1 promoter methylation was analyzed via bisulfite sequencing using primers focused on the core promoter region. The expression levels of BRCA1 and IGF1R were assessed by immunohistochemistry and real-time polymerase chain reaction. Knockdown and overexpression of BRCA1 were achieved using a lentiviral vector in 293T and SKOV3 ovarian cancer cells, and primary non-mutated and BRCA1-mutated ovarian cancer cells. The present study demonstrated that IGF1R expression is increased in non-BRCA1-mutated ovarian cancer when compared with adjacent normal tissue. Furthermore, IGF1R levels are additionally significantly elevated in BRCA1 inactivation ovarian cancer (BRCA1 mutation or hypermethylated BRCA1 promoter). In addition, BRCA1 knockdown was found to be an effective method of activating IGF1R expression in non-BRCA1-mutated ovarian cancer cells. The observations of the current study indicate that BRCA1 may be a potential trigger that is involved in the transcriptional regulation of IGF1R in the development of ovarian cancer.
PMCID: PMC3997726  PMID: 24765210
breast cancer 1; insulin-like growth factor 1 receptor; ovarian cancer

Results 1-25 (983511)