Search tips
Search criteria

Results 1-22 (22)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Telomere Content and Risk of Second Malignant Neoplasm in Survivors of Childhood Cancer: A Report from the Childhood Cancer Survivor Study 
Shorter constitutional telomere length has been associated with increased cancer incidence. Furthermore, telomere shortening is observed in response to intensive chemotherapy and/or ionizing radiation exposure. We aimed to determine if less telomere content was associated with treatment-related second malignant neoplasms (SMNs) in childhood cancer survivors.
Using a nested case-control design, 147 cancer survivors with breast cancer, thyroid cancer, or sarcoma developing after treatment for childhood cancer (cases) were matched (1:1) with childhood cancer survivors without a SMN (controls). Cases and controls were matched by primary cancer diagnosis, years since diagnosis, age at time of sample collection, years of follow up from childhood cancer diagnosis, exposure to specific chemotherapy agents, and to specific radiation fields. We performed conditional logistic regression using telomere content (TC) as a continuous variable to estimate odds ratios (ORs) with corresponding 95% confidence intervals (CI) for development of SMN. ORs were also estimated for specific SMN types, i.e., breast cancer, thyroid cancer, and sarcoma.
There was an inverse relationship between TC and SMN, with an adjusted OR of 0.3 per unit change in telomere length to single copy gene ratio (95% CI, 0.09–1.02, p=0.05). Patients with thyroid cancer SMN were less likely to have more telomere content (OR 0.04, 95% CI, 0.00–0.55, p=0.01), but statistically significant associations could not be demonstrated for breast cancer or sarcoma.
A relation between less telomere content and treatment-related thyroid cancer was observed, suggesting that shorter telomeres may contribute to certain SMNs in childhood cancer survivors.
PMCID: PMC3944671  PMID: 24277454
telomere; second malignant neoplasm; risk; childhood cancer
2.  Joint Effects of Germ-Line p53 Mutation, MDM2 SNP309, and Gender on Cancer Risk in Family Studies of Li-Fraumeni Syndrome 
Human genetics  2011;129(6):663-673.
Li-Fraumeni syndrome (LFS) is a rare familial cancer syndrome characterized by early cancer onset, diverse tumor types, and multiple primary tumors. Germ-line p53 mutations have been identified in most LFS families. A high-frequency genetic variant of single-nucleotide polymorphism (SNP) 309 in the MDM2 gene was recently confirmed to be a modifier of cancer risk in several case-control studies: substantially earlier cancer onset was observed in SNP309 G-allele carriers than in wild-type individuals by 7–16 years. However, risk analyses in family studies that jointly account for measured hereditary p53 mutations and SNP309 have not been evaluated. Here, we extended the statistical method that we recently developed to determine the combined effects of measured p53 mutations, SNP309, and gender and their interactions simultaneously. The method is structured for age-specific risk models based on Cox proportional hazards regression for censored age-of-onset traits. We analyzed the cancer incidence in 19 extended pedigrees with multiple germ-line p53 mutations ascertained through clinical LFS phenotype. The dataset consisted of 463 individuals with 129 p53 mutation carriers. Our analyses showed that the p53 germ-line mutation and its interaction with gender were strongly associated with familial cancer incidence and that the association between SNP309 and increased cancer risk was modest. In contrast with several outcomes in case-control studies, the interaction between SNP309 and p53 mutation was not statistically significant. The causal role of SNP309 in family studies was consistent with a previous finding that SNP309 G-alleles are associated with accelerated tumor formation in patients with sporadic and hereditary cancers.
PMCID: PMC4194062  PMID: 21305319
3.  Young Onset HER2 Positive Breast Cancer is Associated with Germline TP53 Mutations 
Cancer  2011;118(4):908-913.
Germline TP53 mutations predispose to early onset breast cancer (BC) in women and are associated with the Li Fraumeni syndrome. Published data on the pathological characteristics of breast cancer among women with TP53 mutations is limited.
We retrospectively reviewed clinical records of women who had genetic testing for suspected germline TP53 mutations and who were diagnosed with BC between 2000 to 2011. The pathological characteristics of the breast tumors from women testing positive (cases) for a mutation were compared to those testing negative (controls).
Patients who tested positive for germline TP53 mutations (N=30) were compared to (N=79) controls. Human epidermal growth factor receptor 2 (HER2) amplification and/or overexpression was found in 67% of the tumors from the cases, compared to 25% for the controls (p=0.0001). Among patients with a mutation, 70% had estrogen receptor and/or progesterone receptor positive tumors, compared to 68% in the control group (p= 0.87). After adjusting for age at BC diagnosis, having a HER2 positive tumor increased the odds of testing positive for a germline TP53 mutation (OR, 6.9, 95% CI, 2.6 to 18.2). For each yearly increments in age at BC diagnosis, there was decreased likelihood of having a TP53 mutation by 5% (OR=0.95, CI 0.91 to 0.99).
This study suggests an association between germline TP53 mutations and early onset HER2 positive breast cancer. If confirmed in a larger cohort, these results could guide genetic testing strategies, lead to chemoprevention trials incorporating HER2 targeted therapies, and elucidate some of the molecular pathways involved in breast cancer.
PMCID: PMC3527897  PMID: 21761402
4.  Evaluation of a Decision Aid for Families Considering p53 Genetic Counseling and Testing 
Li-Fraumeni syndrome (LFS) is associated with p53 germline mutations, and carriers are at increased risk for multiple primary cancers. We evaluated outcomes following the administration of a video-based decision aid (DA) prior to clinical p53 genetic counseling and testing among persons who had previously participated in cancer genetics research.
Fifty-seven individuals at risk for a known p53 mutation completed baseline and post-DA measures of psychological outcomes, plus knowledge and attitudes regarding p53 genetic testing. Counseling and testing uptake also was recorded.
At baseline, multivariate analysis showed that greater testing intention was associated with lower decisional conflict (p<0.01). Compared with baseline data, multivariate analyses of post-DA outcomes showed that knowledge about LFS and genetic testing increased and decisional conflict related to testing decreased (p< 0.001). Mean cancer worries scores decreased among all participants (p<0.001), and mean depression scores decreased for males (p<0.05). Thirty-nine (68%) completed pre-test genetic counseling and 23 (40%) subsequently gave a blood sample for clinical genetic testing.
This intervention was useful as an initial outreach and educational method for families considering p53 genetic testing, and may improve knowledge about LFS as well as psychological outcomes.
PMCID: PMC4145599  PMID: 16617243
p53; decision aid; genetic counseling; genetic testing; psychosocial
5.  Increased Oxidative Metabolism in the Li–Fraumeni Syndrome 
The New England journal of medicine  2013;368(11):1027-1032.
There is growing evidence that alterations in metabolism may contribute to tumorigenesis. Here, we report on members of families with the Li–Fraumeni syndrome who carry germline mutations in TP53, the gene encoding the tumor-suppressor protein p53. As compared with family members who are not carriers and with healthy volunteers, family members with these mutations have increased oxidative phosphorylation of skeletal muscle. Basic experimental studies of tissue samples from patients with the Li–Fraumeni syndrome and a mouse model of the syndrome support this in vivo finding of increased mitochondrial function. These results suggest that p53 regulates bioenergetic homeostasis in humans. (Funded by the National Heart, Lung, and Blood Institute and the National Institutes of Health; number, NCT00406445.)
PMCID: PMC4123210  PMID: 23484829
6.  Identification of TP53 as an Acute Lymphocytic Leukemia Susceptibility Gene Through Exome Sequencing 
Pediatric blood & cancer  2012;60(6):E1-E3.
Although acute lymphocytic leukemia (ALL) is the most common childhood cancer, genetic predisposition to ALL remains poorly understood. Whole-exome sequencing was performed in an extended kindred in which five individuals had been diagnosed with leukemia. Analysis revealed a nonsense variant of TP53 which has been previously reported in families with sarcomas and other typical Li Fraumeni syndrome-associated cancers but never in a familial leukemia kindred. This unexpected finding enabled identification of an appropriate sibling bone marrow donor and illustrates that exome sequencing will reveal atypical clinical presentations of even well-studied genes.
PMCID: PMC3926299  PMID: 23255406
exome sequencing; acute lymphocytic leukemia; genetic predisposition to disease; genetic testing
7.  Li-Fraumeni syndrome: report of a clinical research workshop and creation of a research consortium 
Cancer genetics  2012;205(10):479-487.
Li-Fraumeni syndrome (LFS) is a rare dominantly inherited cancer predisposition syndrome that was first described in 1969. In most families, it is caused by germline mutations in the TP53 gene and is characterized by early onset of multiple specific cancers and very high lifetime cumulative cancer risk. Despite significant progress in understanding the molecular biology of TP53, the optimal clinical management of this syndrome is poorly defined. We convened a workshop on November 2, 2010, at the National Institutes of Health in Bethesda, Maryland, bringing together clinicians and scientists, as well as individuals from families with LFS, to review the state of the science, address clinical management issues, stimulate collaborative research, and engage the LFS family community. This workshop also led to the creation of the Li-Fraumeni Exploration (LiFE) Research Consortium.
PMCID: PMC3593717  PMID: 22939227
Li-Fraumeni syndrome; hereditary cancer predisposition syndrome; TP53 mutations
8.  Evaluation of Polymorphisms in EWSR1 and Risk of Ewing Sarcoma: A Report from the Childhood Cancer Survivor Study 
Pediatric blood & cancer  2011;59(1):52-56.
Ewing sarcoma is a malignant bone tumor characterized by a high frequency of somatic EWSR1 translocations. Ewing sarcoma is less common in people of African or African-American ancestry, suggesting a genetic etiology.
Germline DNA from white patients with Ewing sarcoma (n = 135), white controls with Wilms tumor (n = 200), and African-American controls (n = 285) was genotyped at 21 SNPs in the EWSR1 gene. Intron 7 of EWSR1, the most common site of translocation, was also sequenced in all subjects. Genetic variation between groups was evaluated statistically using exact logistic regression and Fisher exact tests.
One SNP in EWSR1 (rs2857461) showed a low level of statistical association with the diagnosis of Ewing sarcoma compared to Wilms tumor. The odds ratio for having Ewing sarcoma in people with at least one copy of the minor allele of rs2857461 was 3.57 (95% confidence interval 0.79 – 21.7; p = 0.07). No other SNPs or variations in intron 7 of EWSR1 were associated with Ewing sarcoma. The median relative difference in minor allele frequencies between white subjects with Ewing sarcoma and African-American controls at the evaluated EWSR1 SNPs was 45%.
Variations in EWSR1 at known SNPs or across intron 7 are not associated with the diagnosis of Ewing sarcoma. EWSR1 does not appear to be a Ewing sarcoma susceptibility gene. The genetic basis for this disease remains unknown.
PMCID: PMC3204324  PMID: 21793187
Ewing sarcoma; EWSR1; single nucleotide polymorphism; genetic epidemiology
10.  Clinically Relevant Changes in Family History of Cancer Over Time 
Jama  2011;306(2):172-178.
Knowledge of family cancer history is important for assessing cancer risk and guiding screening recommendations.
To quantify how often throughout adulthood clinically significant changes occur in cancer family history that would result in recommendations for earlier or intense screening.
Design and Setting
Descriptive study examining baseline and follow-up family history data from participants in the Cancer Genetics Network (CGN), a US national population-based cancer registry, between 1999 and 2009.
Adults with a personal history, family history, or both of cancer enrolled in the CGN through population-based cancer registries. Retrospective colorectal, breast, and prostate cancer screening-specific analyses included 9861, 2547, and 1817 participants, respectively; prospective analyses included 1533, 617, and 163 participants, respectively. Median follow-up was 8 years (range, 0–11 years). Screening-specific analyses excluded participants with the cancer of interest.
Main Outcome Measures
Percentage of individuals with clinically significant family histories and rate of change over 2 periods: (1) retrospectively, from birth until CGN enrollment and (2) prospectively, from enrollment to last follow-up.
Retrospective analysis revealed that the percentages of participants who met criteria for high-risk screening based on family history at ages 30 and 50 years, respectively, were as follows: for colorectal cancer, 2.1% (95% confidence interval [CI], 1.8%–2.4%) and 7.1% (95% CI, 6.5%–7.6%); for breast cancer, 7.2% (95% CI, 6.1%–8.4%) and 11.4% (95% CI, 10.0%–12.8%); and for prostate cancer, 0.9% (95% CI, 0.5%–1.4%) and 2.0% (95% CI, 1.4%–2.7%). In prospective analysis, the numbers of participants who newly met criteria for high-risk screening based on family history per 100 persons followed up for 20 years were 2 (95% CI, 0–7) for colorectal cancer, 6 (95% CI, 2–13) for breast cancer, and 8 (95% CI, 3–16) for prostate cancer. The rate of change in cancer family history was similar for colorectal and breast cancer between the 2 analyses.
Clinically relevant family history of colorectal, breast, and prostate cancer that would result in recommendations for earlier or intense cancer screening increases between ages 30 and 50 years, although the absolute rate is low for prostate cancer.
PMCID: PMC3367662  PMID: 21750294
11.  Identification of Genetic Susceptibility to Childhood Cancer through Analysis of Genes in Parallel 
Cancer genetics  2011;204(1):19-25.
Clinical cancer genetic susceptibility analysis typically proceeds sequentially beginning with the most likely causative gene. The process is time consuming and the yield is low particularly for families with unusual patterns of cancer. We determined the results of in parallel mutation analysis of a large cancer-associated gene panel. We performed deletion analysis and sequenced the coding regions of 45 genes (8 oncogenes and 37 tumor suppressor or DNA repair genes) in 48 childhood cancer patients who also (1) were diagnosed with a second malignancy under age 30, (2) have a sibling diagnosed with cancer under age 30 and/or (3) have a major congenital anomaly or developmental delay. Deleterious mutations were identified in 6 of 48 (13%) families, 4 of which met the sibling criteria. Mutations were identified in genes previously implicated in both dominant and recessive childhood syndromes including SMARCB1, PMS2, and TP53. No pathogenic deletions were identified. This approach has provided efficient identification of childhood cancer susceptibility mutations and will have greater utility as additional cancer susceptibility genes are identified. Integrating parallel analysis of large gene panels into clinical testing will speed results and increase diagnostic yield. The failure to detect mutations in 87% of families highlights that a number of childhood cancer susceptibility genes remain to be discovered.
PMCID: PMC3075924  PMID: 21356188
Cancer susceptibility; tumor suppressor genes; oncogenes; mutation analysis; rhabdoid tumors
12.  Variants at 6q21 implicate PRDM1 in the etiology of therapy-induced second malignancies after Hodgkin lymphoma 
Nature medicine  2011;17(8):941-943.
Survivors of pediatric Hodgkin lymphoma (HL) are at significant risk for radiation therapy (RT)-induced second malignant neoplasms (SMNs). We identified two variants at chromosome 6q21 associated with SMNs in HL survivors treated with RT as children but not as adults. The variants comprise a risk locus associated with decreased basal PRDM1 expression and impaired induction of PRDM1 by radiation exposure. These data suggest a novel gene-exposure interaction that may implicate PRDM1 in the etiology of RT-induced SMNs.
PMCID: PMC3229923  PMID: 21785431
13.  Activating mutation in MET oncogene in familial colorectal cancer 
BMC Cancer  2011;11:424.
In developed countries, the lifetime risk of developing colorectal cancer (CRC) is 5%, and it is the second leading cause of death from cancer. The presence of family history is a well established risk factor with 25-35% of CRCs attributable to inherited and/or familial factors. The highly penetrant inherited colon cancer syndromes account for approximately 5%, leaving greater than 20% without clear genetic definition. Familial colorectal cancer has been linked to chromosome 7q31 by multiple affected relative pair studies. The MET proto-oncogene which resides in this chromosomal region is considered a candidate for genetic susceptibility.
MET exons were amplified by PCR from germline DNA of 148 affected sibling pairs with colorectal cancer. Amplicons with altered sequence were detected with high-resolution melt-curve analysis using a LightScanner (Idaho Technologies). Samples demonstrating alternative melt curves were sequenced. A TaqMan assay for the specific c.2975C >T change was used to confirm this mutation in a cohort of 299 colorectal cancer cases and to look for allelic amplification in tumors.
Here we report a germline non-synonymous change in the MET proto-oncogene at amino acid position T992I (also reported as MET p.T1010I) in 5.2% of a cohort of sibling pairs affected with CRC. This genetic variant was then confirmed in a second cohort of individuals diagnosed with CRC and having a first degree relative with CRC at prevalence of 4.1%. This mutation has been reported in cancer cells of multiple origins, including 2.5% of colon cancers, and in <1% in the general population. The threonine at amino acid position 992 lies in the tyrosine kinase domain of MET and a change to isoleucine at this position has been shown to promote metastatic behavior in cell-based models. The average age of CRC diagnosis in patients in this study is 63 years in mutation carriers, which is 8 years earlier than the general population average for CRC.
Although the MET p.T992I genetic mutation is commonly found in somatic colorectal cancer tissues, this is the first report also implicating this MET genetic mutation as a germline inherited risk factor for familial colorectal cancer. Future studies on the cancer risks associated with this mutation and the prevalence in different at-risk populations will be an important extension of this work to define the clinical significance.
PMCID: PMC3202244  PMID: 21970370
14.  Effects of Measured Susceptibility Genes on Cancer Risk in Family Studies 
Human genetics  2009;127(3):349-357.
Numerous family studies have been performed to assess the associations between cancer incidence and genetic and non-genetic risk factors and to quantitatively evaluate the cancer risk attributable to these factors. However, mathematical models that account for a measured hereditary susceptibility gene have not been fully explored in family studies. In this report, we proposed statistical approaches to precisely model a measured susceptibility gene fitted to family data and simultaneously determine the combined effects of individual risk factors and their interactions. Our approaches are structured for age-specific risk models based on Cox proportional hazards regression methods. They are useful for analyses of families and extended pedigrees in which measured risk genotypes are segregated within the family and are robust even when the genotypes are available only in some members of a family. We exemplified these methods by analyzing 6 extended pedigrees ascertained through soft-tissue sarcoma patients with p53 germ-line mutations. Our analyses showed that germ-line p53 mutations and sex had significant interaction effects on cancer risk. Our proposed methods in family studies are accurate and robust for assessing age-specific cancer risk attributable to a measured hereditary susceptibility gene, providing valuable inferences for genetic counseling and clinical management.
PMCID: PMC2918266  PMID: 20039063
15.  Wt1 ablation and Igf2 upregulation in mice result in Wilms tumors with elevated ERK1/2 phosphorylation  
Wilms tumor (WT) is a genetically heterogeneous childhood kidney tumor. Several genetic alterations have been identified in WT patients, including inactivating mutations in WT1 and loss of heterozygosity or loss of imprinting at 11p15, which results in biallelic expression of IGF2. However, the mechanisms by which one or a combination of genetic alterations results in tumorigenesis has remained challenging to determine, given the lack of a mouse model of WT. Here, we engineered mice to sustain mosaic, somatic ablation of Wt1 and constitutional Igf2 upregulation, mimicking a subset of human tumors. Mice with this combination of genetic alterations developed tumors at an early age. Mechanistically, Wt1 ablation blocked mesenchyme differentiation, and increased Igf2 expression upregulated ERK1/2 phosphorylation. Importantly, a subset of human tumors similarly displayed upregulation of ERK1/2 phosphorylation, which suggests ERK signaling might contribute to WT development. Thus, we have generated a biologically relevant mouse model of WT and defined one combination of driver alterations for WT. This mouse model will provide a powerful tool to study the biology of WT initiation and progression and to investigate therapeutic strategies for cancers with IGF pathway dysregulation.
PMCID: PMC3007149  PMID: 21123950
16.  Common Familial Colorectal Cancer Linked to Chromosome 7q31: a genome-wide analysis 
Cancer research  2008;68(21):8993-8997.
Present investigations suggest that approximately 30% of colorectal cancer (CRC) cases arise on the basis of inherited factors. We hypothesize that the majority of inherited factors are moderately penetrant genes, common in the population. We use an affected sibling pair approach to identify genetic regions that are coinherited by siblings with CRC. Individuals from families with at least two siblings diagnosed with colorectal adenocarcinoma or high grade dysplasia were enrolled. Known familial CRC syndromes were excluded. A genome-wide scan on 151 DNA samples from 70 kindreds was completed using deCODE's 1100 short tandem repeat marker set at an average 4 cM density. Fine mapping on a total of 184 DNAs from 83 kindreds was done in regions suggesting linkage. Linkage analysis was accomplished with MERLIN analysis package. Linkage analysis revealed three genetic regions with NPL LOD scores ≥ 2.0: Ch. 3q29, LOD 2.61 (p=0.0003); Ch. 4q31.3, LOD 2.13 (p=0.0009); and Ch. 7q31.31, LOD 3.08 (p=0.00008). Affected siblings with increased sharing at the 7q31 locus have an 3.8 year (±3.5) earlier age of CRC onset although this is not statistically significant (p=0.11). No significant linkage was found near genes causing known syndromes or, regions previously reported (8q24, 9q22, and 11q23). The chromosome 3q21-q24 region reported to be linked in CRC relative pairs, is supported by our study, albeit a minor peak (LOD 0.9, p=0.02). No known familial cancer genes reside in the 7q31 locus, thus the identified region may contain a novel susceptibility gene responsible for common familial CRC.
PMCID: PMC2927856  PMID: 18974144
sibpair; genetic linkage; colorectal cancer; 7q31
17.  Effects of MDM2, MDM4 and TP53 Codon 72 Polymorphisms on Cancer Risk in a Cohort Study of Carriers of TP53 Germline Mutations 
PLoS ONE  2010;5(5):e10813.
Previous studies have shown that MDM2 SNP309 and p53 codon 72 have modifier effects on germline P53 mutations, but those studies relied on case-only studies with small sample sizes. The impact of MDM4 polymorphism on tumor onset in germline mutation carriers has not previously been studied.
Methodology/Principal Findings
We analyzed 213 p53 germline mutation carriers including 168(78.9%) affected with cancer and 174 who had genotypic data. We analyzed time to first cancer using Kaplan-Meier and Cox proportional hazards methods, comparing risks according to polymorphism genotypes. For MDM2 SNP309, a significant difference of 9.0 years in the average age of cancer diagnosis was observed between GG/GT and TT carriers (18.6 versus 27.6 years, P = 0.0087). The hazards ratio was 1.58 (P = 0.03) comparing risks among individuals with GG/GT to risk among TT, but this effect was only significant in females (HR = 1.60, P = 0.02). Compared to other genotypes, P53 codon 72 PP homozygotes had a 2.24 times (P = 0.03) higher rate for time to develop cancer. We observed a multiplicative joint effect of MDM2 and p53 codon72 polymorphism on risk. The MDM4 polymorphism had no significant effects.
Our results suggest that the MDM2 SNP309 G allele is associated with cancer risk in p53 germline mutation carriers and accelerates time to cancer onset with a pronounced effect in females. A multiplicative joint effect exists between the MDM2 SNP309 G allele and the p53 codon 72 G allele in the risk of cancer development. Our results further define cancer risk in carriers of germline p53 mutations.
PMCID: PMC2877078  PMID: 20520810
18.  The Childhood Cancer Survivor Study: A National Cancer Institute–Supported Resource for Outcome and Intervention Research 
Journal of Clinical Oncology  2009;27(14):2308-2318.
Survival for childhood cancer has increased dramatically over the last 40 years with 5-year survival rates now approaching 80%. For many diagnostic groups, rapid increases in survival began in the 1970s with the broader introduction of multimodality approaches, often including combination chemotherapy with or without radiation therapy. With this increase in rates of survivorship has come the recognition that survivors are at risk for adverse health and quality-of-life outcomes, with risk being influenced by host-, disease-, and treatment-related factors. In 1994, the US National Cancer Institute funded the Childhood Cancer Survivor Study, a multi-institutional research initiative designed to establish a large and extensively characterized cohort of more than 14,000 5-year survivors of childhood and adolescent cancer diagnosed between 1970 and 1986. This ongoing study, which reflects the single most comprehensive body of information ever assembled on childhood and adolescent cancer survivors, provides a dynamic framework and resource to investigate current and future questions about childhood cancer survivors.
PMCID: PMC2677920  PMID: 19364948
19.  Analysis of genomic instability in Li-Fraumeni fibroblasts with germline p53 mutations 
Oncogene  1996;12(11):2267-2278.
Germline p53 mutations are frequently observed in the normal DNA of cancer-prone patients with Li-Fraumeni syndrome (LFS). Fibroblasts from LFS patients develop chromosomal aberrations, loss of cell cycle control, and spontaneous immortalization. We transfected four different mutant p53 genes into human skin fibroblasts from normal donors with two copies of wild-type p53 (p53wt/wt). Each mutant p53 expression-plasmid induced genomic instability equivalent to that seen in LFS cells. To test the role of wild-type and mutant p53 alleles in DNA replication and fidelity in LFS cells, we analysed the replication of the SV40-based shuttle vector pZ189 in four types of cells. We used p53wt/mut and p53mut/− LFS fibroblasts, and p53−/− non-LFS cells. Replication of pZ189 in vivo was significantly reduced by the presence of a p53wt allele. To show that this was not just due to inhibition of the function of T-antigen in SV40-based replication, we constructed a shuttle vector, pZ402, that contains a mutation in SV40 T-antigen which blocks its ability to interact with p53. Replication of pZ402 in LFS cells was also reduced by the presence of p53wt, indicating that p53 can inhibit replication by interacting with proteins within the cellular replication machinery. Replicative errors in this shuttle vector are detected as mutations in a marker gene, supF. In addition to supF mutations, we observed deletion of a portion of the SV40 T-antigen gene in 100% of replicated plasmid pZ189 mutants (supF−) from the p53wt/mut fibroblasts and in 88% of the supF− mutants from the p53mut/− (amino acid 175 arg to his) LFS cells. In one cell strain of immortal LFS cells, p53mut/−, containing a p53 frameshift mutation at amino acid 184, pZ189 replication yielded very few of these deleted shuttle vector plasmids (15%). These large deletions were not detected in plasmids replicated in p53−/− non-LFS cells, Saos-2 cells. Replicated plasmids with a normal supF gene were never found to have this large deletion regardless of the cell from which they were derived. Because the supF gene is not in the same region of the shuttle vector as the T-antigen gene it appears that second, independent gene deletions are frequent when replicative errors in supF occur in cells with a mutant p53. We conclude, therefore, that p53wt/mut LFS cells contain an activity that promotes mutations. Such an activity, which is likely to be due to the p53mut, could result in the high rate of chromosomal instability and allelic loss of the wild-type p53 observed as these cells spontaneously immortalize.
PMCID: PMC2719722  PMID: 8649766
tumor suppressor gene; germline mutations; chromosome instability; shuttle vector mutagenesis; DNA replication
20.  Validity of Models for Predicting BRCA1 and BRCA2 Mutations 
Annals of internal medicine  2007;147(7):441-450.
Deleterious mutations of the BRCA1 and BRCA2 genes confer susceptibility to breast and ovarian cancer. At least 7 models for estimating the probabilities of having a mutation are used widely in clinical and scientific activities; however, the merits and limitations of these models are not fully understood.
To systematically quantify the accuracy of the following publicly available models to predict mutation carrier status: BRCAPRO, family history assessment tool, Finnish, Myriad, National Cancer Institute, University of Pennsylvania, and Yale University.
Cross-sectional validation study, using model predictions and BRCA1 or BRCA2 mutation status of patients different from those used to develop the models.
Multicenter study across Cancer Genetics Network participating centers.
3 population-based samples of participants in research studies and 8 samples from genetic counseling clinics.
Discrimination between individuals testing positive for a mutation in BRCA1 or BRCA2 from those testing negative, as measured by the c-statistic, and sensitivity and specificity of model predictions.
The 7 models differ in their predictions. The better-performing models have a c-statistic around 80%. BRCAPRO has the largest c-statistic overall and in all but 2 patient subgroups, although the margin over other models is narrow in many strata. Outside of high-risk populations, all models have high false-negative and false-positive rates across a range of probability thresholds used to refer for mutation testing.
Three recently published models were not included.
All models identify women who probably carry a deleterious mutation of BRCA1 or BRCA2 with adequate discrimination to support individualized genetic counseling, although discrimination varies across models and populations.
PMCID: PMC2423214  PMID: 17909205
21.  Characterization of BRCA1 and BRCA2 Mutations in a Large United States Sample 
An accurate evaluation of the penetrance of BRCA1 and BRCA2 mutations is essential to the identification and clinical management of families at high risk of breast and ovarian cancer. Existing studies have focused on Ashkenazi Jews (AJ) or on families from outside the United States. In this article, we consider the US population using the largest US-based cohort to date of both AJ and non-AJ families.
We collected 676 AJ families and 1,272 families of other ethnicities through the Cancer Genetics Network. Two hundred eighty-two AJ families were population based, whereas the remainder was collected through counseling clinics. We used a retrospective likelihood approach to correct for bias induced by oversampling of participants with a positive family history. Our approach takes full advantage of detailed family history information and the Mendelian transmission of mutated alleles in the family.
In the US population, the estimated cumulative breast cancer risk at age 70 years was 0.46 (95% CI, 0.39 to 0.54) in BRCA1 carriers and 0.43 (95% CI, 0.36 to 0.51) in BRCA2 carriers, whereas ovarian cancer risk was 0.39 (95% CI, 0.30 to 0.50) in BRCA1 carriers and 0.22 (95% CI, 0.14 to 0.32) in BRCA2 carriers. We also reported the prospective risks of developing cancer for cancer-free carriers in 10-year age intervals. We noted a rapid decrease in the relative risk of breast cancer with age and derived its implication for genetic counseling.
The penetrance of BRCA mutations in the United States is largely consistent with previous studies on Western populations given the large CIs on existing estimates. However, the absolute cumulative risks are on the lower end of the spectrum.
PMCID: PMC2323978  PMID: 16484695
22.  An Information-Theoretic Analysis of Genetics, Gender and Age in Cancer Patients 
PLoS ONE  2008;3(4):e1951.
Germline genetics, gender and hormonal-signaling pathways are all well described modifiers of cancer risk and progression. Although an improved understanding of how germline genetic variants interact with other cancer risk factors may allow better prevention and treatment of human cancer, measuring and quantifying these interactions is challenging. In other areas of research, Information Theory has been used to quantitatively describe similar multivariate interactions. We implemented a novel information-theoretic analysis to measure the joint effect of a high frequency germline genetic variant of the p53 tumor suppressor pathway (MDM2 SNP309 T/G) and gender on clinical cancer phenotypes. This analysis quantitatively describes synergistic interactions among gender, the MDM2 SNP309 locus, and the age of onset of tumorigenesis in p53 mutation carriers. These results offer a molecular and genetic basis for the observed sexual dimorphism of cancer risk in p53 mutation carriers and a model is proposed that suggests a novel cancer prevention strategy for p53 mutation carriers.
PMCID: PMC2276689  PMID: 18398474

Results 1-22 (22)