PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-11 (11)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
Document Types
1.  De novo constitutional MLH1 epimutations confer early-onset colorectal cancer in two new sporadic Lynch syndrome cases, with derivation of the epimutation on the paternal allele in one 
Lynch syndrome is an autosomal dominant cancer predisposition syndrome classically caused by germline mutations of the mismatch repair genes, MLH1, MSH2, MSH6 and PMS2. Constitutional epimutations of the MLH1 gene, characterized by soma-wide methylation of a single allele of the promoter and allelic transcriptional silencing, have been identified in a subset of Lynch syndrome cases lacking a sequence mutation in MLH1. We report two individuals with no family history of colorectal cancer who developed that disease at age 18 and 20 years. In both cases, cancer had arisen because of the de novo occurrence of a constitutional MLH1 epimutation and somatic loss-of-heterozygosity of the functional allele in the tumors. We show for the first time that the epimutation in one case arose on the paternally inherited allele. Analysis of 13 tumors from seven individuals with constitutional MLH1 epimutations showed eight tumors had lost the second MLH1 allele, two tumors had a novel pathogenic missense mutation and three had retained heterozygosity. Only 1 of 12 tumors demonstrated the BRAF V600E mutation and 3 of 11 tumors harbored a mutation in KRAS. The finding that epimutations can originate on the paternal allele provides important new insights into the mechanism of origin of epimutations. It is clear that the second hit in MLH1 epimutation-associated tumors typically has a genetic not epigenetic basis. Individuals with mismatch repair–deficient cancers without the BRAF V600E mutation are candidates for germline screening for sequence or methylation changes in MLH1.
doi:10.1002/ijc.25422
PMCID: PMC3794437  PMID: 20473912
colorectal cancer; Lynch syndrome; MLH1 epimutation; microsatellite instability; BRAF
2.  The importance of distinguishing pseudogenes from parental genes 
Clinical Epigenetics  2014;6(1):90.
doi:10.1186/s13148-014-0033-5
PMCID: PMC4280768  PMID: 25553138
3.  Nucleosome positioning is unaltered at MLH1 splice site mutations in cells derived from Lynch syndrome patients 
Clinical Epigenetics  2014;6(1):32.
Background
Splicing is more efficient when coupled with transcription and it has been proposed that nucleosomes enriched in exons are important for splice site recognition. Lynch syndrome is a familial cancer syndrome that can be caused by the autosomal dominant inheritance of splice site mutations in the MutL homolog 1 (MLH1) gene. To better understand the role of nucleosomes in splicing, we used MLH1 splice site mutations in Lynch syndrome cases as a model to investigate if abnormal splicing was associated with altered nucleosome positioning at exon-intron boundaries.
Findings
Nucleosome Occupancy and Methylome sequencing (NOMe-seq) was used to determine the allele-specific positioning of nucleosomes around heterozygous splice site mutations in lymphoblastoid cells lines (LCLs) derived from six Lynch syndrome patients. These mutations were previously shown to cause exon skipping in five of the six patients. Allele-specific high-resolution nucleosome mapping across exons and exon-intron boundaries revealed high levels of nucleosomes across all regions examined. Alleles containing donor or acceptor splice site mutations showed no consistent alteration in nucleosome positioning or occupancy.
Conclusion
Nucleosomes were enriched at MLH1 exons in LCLs derived from Lynch syndrome patients, and in this model system the positioning of nucleosomes was unaltered at exon-intron boundaries containing splice site mutations. Thus, these splice site mutations alone do not significantly change the local organisation of nucleosomes.
doi:10.1186/s13148-014-0032-6
PMCID: PMC4272815  PMID: 25530820
Lynch syndrome; Colorectal cancer; Nucleosome; Splice site; Splicing; Acceptor; Donor; Exon
4.  Low meprin α expression differentiates primary ovarian mucinous carcinoma from gastrointestinal cancers that commonly metastasise to the ovaries 
Journal of Clinical Pathology  2006;60(6):622-626.
Background
Currently, no specific immunohistochemical markers are available to differentiate primary mucinous epithelial ovarian cancer (MOC) from adenocarcinomas originating at other sites that have metastasised to the ovary, which may have an impact on patient management and prognosis.
Aim
To investigate the expression of two intestinal markers, galectin 4 and meprin α, in mucinous carcinomas of the ovary and gastrointestinal tract.
Methods
Using immunohistochemical analysis, the expression of galectin 4 and meprin α was investigated in 10 MOCs and in 38 mucinous adenocarcinomas of colon, pancreas, stomach and appendix, the most common sites of origin of ovarian metastases.
Results
Total cytoplasmic galectin 4 expression was relatively consistent between the different carcinomas. Membranous meprin α expression was significantly lower in MOCs compared with gastrointestinal carcinomas. Moreover, meprin α expression showed greater discrimination between the ovarian and gastrointestinal carcinomas than the cytokeratins CK7 and CK20, the current standard immunohistochemical markers used to determine the tissue origin of mucinous carcinomas involving the ovaries.
Conclusions
Meprin α is a useful additional marker in differentiating primary from secondary mucinous adenocarcinomas of the ovary.
doi:10.1136/jcp.2005.034223
PMCID: PMC1955076  PMID: 16822880
5.  Reassembly of Nucleosomes at the MLH1 Promoter Initiates Resilencing Following Decitabine Exposure 
PLoS Genetics  2013;9(7):e1003636.
Hypomethylating agents reactivate tumor suppressor genes that are epigenetically silenced in cancer. Inevitably these genes are resilenced, leading to drug resistance. Using the MLH1 tumor suppressor gene as a model, we showed that decitabine-induced re-expression was dependent upon demethylation and eviction of promoter nucleosomes. Following decitabine withdrawal, MLH1 was rapidly resilenced despite persistent promoter demethylation. Single molecule analysis at multiple time points showed that gene resilencing was initiated by nucleosome reassembly on demethylated DNA and only then was followed by remethylation and stable silencing. Taken together, these data establish the importance of nucleosome positioning in mediating resilencing of drug-induced gene reactivation and suggest a role for therapeutic targeting of nucleosome assembly as a mechanism to overcome drug resistance.
Author Summary
Hypomethylating agents are emerging as effective cancer therapies. However, their therapeutic effects are transient and drug resistance inevitably develops. While resistance is associated with resilencing of genes initially demethylated by the drug, the mechanism underlying this resilencing is unknown. We provide evidence that the rapid reassembly of nucleosomes at transcription start sites initiates resilencing and is a prerequisite for promoter remethylation. This finding shows reassembly of nucleosomes at the promoter of critical genes is a potential early marker of resistance to hypomethylating agents. Our findings have implications for the treatment of cancer using epigenetic therapies that target DNA methylation alone, and suggest that overcoming drug resistance will require therapeutic strategies which prevent nucleosome deposition.
doi:10.1371/journal.pgen.1003636
PMCID: PMC3723495  PMID: 23935509
6.  The Wnt signalling pathway is upregulated in an in vitro model of acquired tamoxifen resistant breast cancer 
BMC Cancer  2013;13:174.
Background
Acquired resistance to Tamoxifen remains a critical problem in breast cancer patient treatment, yet the underlying causes of resistance have not been fully elucidated. Abberations in the Wnt signalling pathway have been linked to many human cancers, including breast cancer, and appear to be associated with more metastatic and aggressive types of cancer. Here, our aim was to investigate if this key pathway was involved in acquired Tamoxifen resistance, and could be targeted therapeutically.
Methods
An in vitro model of acquired Tamoxifen resistance (named TamR) was generated by growing the estrogen receptor alpha (ER) positive MCF7 breast cancer cell line in increasing concentrations of Tamoxifen (up to 5 uM). Alterations in the Wnt signalling pathway and epithelial to mesenchymal transition (EMT) in response to Tamoxifen and treatment with the Wnt inhibitor, IWP-2 were measured via quantitative RT-PCR (qPCR) and TOP/FOP Wnt reporter assays. Resistance to Tamoxifen, and effects of IWP-2 treatment were determined by MTT proliferation assays.
Results
TamR cells exhibited increased Wnt signalling as measured via the TOP/FOP Wnt luciferase reporter assays. Genes associated with both the β-catenin dependent (AXIN2, MYC, CSNK1A1) and independent arms (ROR2, JUN), as well as general Wnt secretion (PORCN) of the Wnt signalling pathway were upregulated in the TamR cells compared to the parental MCF7 cell line. Treatment of the TamR cell line with human recombinant Wnt3a (rWnt3a) further increased the resistance of both MCF7 and TamR cells to the anti-proliferative effects of Tamoxifen treatment. TamR cells demonstrated increased expression of EMT markers (VIM, TWIST1, SNAI2) and decreased CDH1, which may contribute to their resistance to Tamoxifen. Treatment with the Wnt inhibitor, IWP-2 inhibited cell proliferation and markers of EMT.
Conclusions
These data support the role of the Wnt signalling pathway in acquired resistance to Tamoxifen. Further research into the mechanism by which activated Wnt signalling inhibits the effects of Tamoxifen should be undertaken. As a number of small molecules targeting the Wnt pathway are currently in pre-clinical development, combinatorial treatment with endocrine agents and Wnt pathway inhibitors may be a useful therapeutic option in the future for a subset of breast cancer patients.
doi:10.1186/1471-2407-13-174
PMCID: PMC3621642  PMID: 23547709
Wnt-signalling; Breast cancer; Tamoxifen resistant; Endocrine resistant; Epithelial to mesenchymal transition (EMT); IWP-2
7.  Uptake of a web-based oncology protocol system: how do cancer clinicians use eviQ cancer treatments online? 
BMC Cancer  2013;13:112.
Background
The use of computerized systems to support evidence-based practice is commonplace in contemporary medicine. Despite the prolific use of electronic support systems there has been relatively little research on the uptake of web-based systems in the oncology setting. Our objective was to examine the uptake of a web-based oncology protocol system (http://www.eviq.org.au) by Australian cancer clinicians.
Methods
We used web-logfiles and Google Analytics to examine the characteristics of eviQ registrants from October 2009-December 2011 and patterns of use by cancer clinicians during a typical month.
Results
As of December 2011, there were 16,037 registrants; 85% of whom were Australian health care professionals. During a typical month 87% of webhits occurred in standard clinical hours (08:00 to 18:00 weekdays). Raw webhits were proportional to the size of clinician groups: nurses (47% of Australian registrants), followed by doctors (20%), and pharmacists (14%). However, pharmacists had up to three times the webhit rate of other clinical groups. Clinicians spent five times longer viewing chemotherapy protocol pages than other content and the protocols viewed reflect the most common cancers: lung, breast and colorectal.
Conclusions
Our results demonstrate eviQ is used by a range of health professionals involved in cancer treatment at the point-of-care. Continued monitoring of electronic decision support systems is vital to understanding how they are used in clinical practice and their impact on processes of care and patient outcomes.
doi:10.1186/1471-2407-13-112
PMCID: PMC3606250  PMID: 23497080
Clinical decision support systems; Evidence-based practice; Cancer chemotherapy protocols; Clinical oncology; Health personnel
8.  The Wnt Gatekeeper SFRP4 Modulates EMT, Cell Migration and Downstream Wnt Signalling in Serous Ovarian Cancer Cells 
PLoS ONE  2013;8(1):e54362.
Aberrant Wnt signalling is implicated in numerous human cancers, and understanding the effects of modulation of pathway members may lead to the development of novel therapeutics. Expression of secreted frizzled related protein 4 (SFRP4), an extracellular modulator of the Wnt signalling pathway, is progressively lost in more aggressive ovarian cancer phenotypes. Here we show that recombinant SFRP4 (rSFRP4) treatment of a serous ovarian cancer cell line results in inhibition of β-catenin dependent Wnt signalling as measured by TOP/FOP Wnt reporter assay and decreased transcription of Wnt target genes, Axin2, CyclinD1 and Myc. In addition, rSFRP4 treatment significantly increased the ability of ovarian cancer cells to adhere to collagen and fibronectin, and decreased their ability to migrate across an inflicted wound. We conclude that these changes in cell behaviour may be mediated via mesenchymal to epithelial transition (MET), as rSFRP4 treatment also resulted in increased expression of the epithelial marker E-cadherin, and reduced expression of Vimentin and Twist. Combined, these results indicate that modulation of a single upstream gatekeeper of Wnt signalling can have effects on downstream Wnt signalling and ovarian cancer cell behaviour, as mediated through epithelial to mesenchymal plasticity (EMP). This raises the possibility that SFRP4 may be used both diagnostically and therapeutically in epithelial ovarian cancer.
doi:10.1371/journal.pone.0054362
PMCID: PMC3543420  PMID: 23326605
9.  A reinvestigation of somatic hypermethylation at the PTEN CpG island in cancer cell lines 
Background
PTEN is an important tumour suppressor gene that is mutated in Cowden syndrome as well as various sporadic cancers. CpG island hypermethylation is another route to tumour suppressor gene inactivation, however, the literature regarding PTEN hypermethylation in cancer is controversial. Furthermore, investigation of the methylation status of the PTEN CpG island is challenging due to sequence homology with the PTEN pseudogene, PTENP1. PTEN shares a CpG island promoter with another gene known as KLLN. Here we present a thorough reinvestigation of the methylation status of the PTEN CpG island in DNA from colorectal, breast, ovarian, glioma, lung and haematological cancer cell lines.
Results
Using a range of bisulphite-based PCR assays we investigated 6 regions across the PTEN CpG island. We found that regions 1-4 were not methylated in cancer cell lines (0/36). By allelic bisulphite sequencing and pyrosequencing methylation was detected in regions 5 and 6 in colorectal, breast and haematological cancer cell lines. However, methylation detected in this region was associated with the PTENP1 promoter and not the PTEN CpG island.
Conclusions
We show that methylation of the PTEN CpG island is a rare event in cancer cell lines and that apparent methylation most likely originates from homologous regions of the PTENP1 pseudogene promoter. Future studies should utilize assays that reliably discriminate between PTEN and PTENP1 to avoid data misinterpretation.
doi:10.1186/1480-9222-14-5
PMCID: PMC3342897  PMID: 22490388
DNA methylation; Epigenetic; PTEN; KILLIN; PTENP1; Pseudogene; Cowden syndrome
10.  Identification of 5 novel genes methylated in breast and other epithelial cancers 
Molecular Cancer  2010;9:51.
Background
There are several high throughput approaches to identify methylated genes in cancer. We utilized one such recently developed approach, MIRA (methylated-CpG island recovery assay) combined with CpG island arrays to identify novel genes that are epigenetically inactivated in breast cancer.
Results
Using this approach we identified numerous CpG islands that demonstrated aberrant DNA methylation in breast cancer cell lines. Using a combination of COBRA and sequencing of bisulphite modified DNA, we confirmed 5 novel genes frequently methylated in breast tumours; EMILIN2, SALL1, DBC1, FBLN2 and CIDE-A. Methylation frequencies ranged from between 25% and 63% in primary breast tumours, whilst matched normal breast tissue DNA was either unmethylated or demonstrated a much lower frequency of methylation compared to malignant breast tissue DNA. Furthermore expression of the above 5 genes was shown to be restored following treatment with a demethylating agent in methylated breast cancer cell lines. We have expanded this analysis across three other common epithelial cancers (lung, colorectal, prostate). We demonstrate that the above genes show varying levels of methylation in these cancers. Lastly and most importantly methylation of EMILIN2 was associated with poorer clinical outcome in breast cancer and was strongly associated with estrogen receptor as well as progesterone receptor positive breast cancers.
Conclusion
The combination of the MIRA assay with CpG island arrays is a very useful technique for identifying epigenetically inactivated genes in cancer genomes and can provide molecular markers for early cancer diagnosis, prognosis and epigenetic therapy.
doi:10.1186/1476-4598-9-51
PMCID: PMC2841122  PMID: 20205715
11.  Identification of constitutional MLH1 epimutations and promoter variants in colorectal cancer patients from the Colon Cancer Family Registry 
Genetics in Medicine  2012;15(1):25-35.
Purpose:
Constitutional MLH1 epimutations manifest as promoter methylation and silencing of the affected allele in normal tissues, predisposing to Lynch syndrome–associated cancers. This study investigated their frequency and inheritance.
Methods:
A total of 416 individuals with a colorectal cancer showing loss of MLH1 expression and without deleterious germline mutations in MLH1 were ascertained from the Colon Cancer Family Registry (C-CFR). Constitutive DNA samples were screened for MLH1 methylation in all 416 subjects and for promoter sequence changes in 357 individuals.
Results:
Constitutional MLH1 epimutations were identified in 16 subjects. Of these, seven (1.7%) had mono- or hemi-allelic methylation and eight had low-level methylation (2%). In one subject the epimutation was linked to the c.-27C>A promoter variant. Testing of 37 relatives from nine probands revealed paternal transmission of low-level methylation segregating with a c.+27G>A variant in one case. Five additional probands had a promoter variant without an MLH1 epimutation, with three showing diminished promoter activity in functional assays.
Conclusion:
Although rare, sequence changes in the regulatory region of MLH1 and aberrant methylation may alone or together predispose to the development of cancer. Screening for these changes is warranted in individuals who have a negative germline sequence screen of MLH1 and loss of MLH1 expression in their tumor.
doi:10.1038/gim.2012.91
PMCID: PMC3908650  PMID: 22878509
colorectal cancer; epimutation; Lynch; methylation; MLH1

Results 1-11 (11)