Microsatellite instability and expression of hMLH1 and hMSH2 proteins in ovarian endometrioid cancer

The prevalence of mismatch repair deficiency in ovarian cancer: a systematic review and meta‐analysis

Ovarian cancer (OC) is the least survivable gynecological malignancy and presents late. Five‐year survival for OC is around 45% increasing the need for innovative treatments. Checkpoint inhibitors have shown significant clinical efficacy in mismatch repair deficient (MMRd) cancers and could be a powerful treatment in OC. However, their application in OC is limited due to the lack of data on the prevalence of MMRd. The aim of our study was to conduct a systematic review of the literature and meta‐analysis to provide an accurate estimate of the prevalence of MMRd in OC. We followed PRISMA guidelines throughout. Studies were identified by electronic searches of Medline, Embase, Cochrane CENTRAL and Web of Science followed by citation searching. Studies not written in English were excluded. All studies were reviewed by at least two independent reviewers. Proportions of test positivity were calculated by random and fixed‐effects meta‐analysis models. I² score was used to assess heterogeneity across studies. In total 54 studies were included with 17 532 analyzed for MMRd. The overall proportions of MMRd by immunohistochemistry and microsatellite instability analysis were 6.7% and 10.4%, respectively. MMRd was reported in all histotypes of epithelial OC but was most common in endometrioid OC. We estimate that on average 46.7% (95% CI: 28.8‐65.4) of ovarian carcinomas showing MMRd by IHC had a germline path_MMR variant identified. OC in those with Lynch syndrome seems to present at an earlier age and stage. Studies however were generally of low quality and there was a high degree of heterogeneity. A significant minority (up to 16%) of OC displays MMRd and, therefore, could be amenable to checkpoint inhibition therapy. However, the current literature base is of limited quality and therefore high‐quality prospective studies exploring MMRd in OC with the use of multimodal testing are required. In addition, trials researching efficacy of checkpoint inhibition in MMRd OC are needed.

Molecular stratification of endometrioid ovarian carcinoma predicts clinical outcome

Endometrioid ovarian carcinoma (EnOC) demonstrates substantial clinical and molecular heterogeneity. Here, we report whole exome sequencing of 112 EnOC cases following rigorous pathological assessment. We detect a high frequency of mutation in CTNNB1 (43%), PIK3CA (43%), ARID1A (36%), PTEN (29%), KRAS (26%), TP53 (26%) and SOX8 (19%), a recurrently-mutated gene previously unreported in EnOC. POLE and mismatch repair protein-encoding genes were mutated at lower frequency (6%, 18%) with significant co-occurrence. A molecular taxonomy is constructed, identifying clinically distinct EnOC subtypes: cases with TP53 mutation demonstrate greater genomic complexity, are commonly FIGO stage III/IV at diagnosis (48%), are frequently incompletely debulked (44%) and demonstrate inferior survival; conversely, cases with CTNNB1 mutation, which is mutually exclusive with TP53 mutation, demonstrate low genomic complexity and excellent clinical outcome, and are predominantly stage I/II at diagnosis (89%) and completely resected (87%). Moreover, we identify the WNT, MAPK/RAS and PI3K pathways as good candidate targets for molecular therapeutics in EnOC.

Incidence of Mismatch Repair Protein Deficiency and Associated Clinicopathologic Features in a Cohort of 104 Ovarian Endometrioid Carcinomas

Patients with Lynch syndrome have up to a 24% risk of developing ovarian carcinoma, but universal mismatch repair (MMR) protein testing of ovarian carcinomas is not standard practice in most institutions. We reviewed 104 unselected ovarian endometrioid carcinomas (OEC) for various clinicopathologic features to determine if any are predictive of MMR loss. Immunohistochemistry for all 4 MMR proteins was performed followed by MLH1 promoter methylation analysis when indicated. Overall, patients had a mean age of 55 years and tumors averaged 12 cm. Most (72%) patients had stage I tumors, 63% were grade 1, and 30% had a synchronous stage IA endometrial endometrioid carcinoma. Peritumoral lymphocytes and intratumoral stromal inflammation were rare, but tumor-infiltrating lymphocytes averaged 47/10 high-power fields. Endometriosis was noted in 71%, adenofibromatous background in 14%, and both in 14% of tumors. Metaplastic changes were common and included squamous metaplasia (63%), clear cell change (32%), mucinous differentiation (24%), and sex cord-like elements (13%). When follow-up was available (n=99), 78% of patients were alive and well, 12% died from disease, 6% died from other causes, and 4% were alive with disease. Unmethylated, MMR-deficient OECs were identified in 7% of the cohort and included MSH2/MSH6 (n=4), MSH6 (n=2), and PMS2 (n=1). All these tumors were stage I, 71% grade 1, and 57% had a synchronous endometrial endometrioid carcinoma. Among patients in this group with follow-up (n=5), all were alive without evidence of disease (mean 150 mo). Given that no clinicopathologic features were associated with MMR deficiency on univariate analysis, this study highlights the importance of universal MMR screening in OECs.

Origins based clinical and molecular complexities of epithelial ovarian cancer

Ovarian cancer is the most lethal of all common gynaecological malignancies in women worldwide. Ovarian cancer comprises of >15 distinct tumor types and subtypes characterized by histopathological features, environmental and genetic risk factors, precursor lesions and molecular events during oncogenesis. Recent studies on gene signature profiling of different subtypes of ovarian cancer have revealed significant genetic heterogeneity between and within each ovarian cancer histological subtype. Thus, an immense interest have shown towards a more personalized medicine for understanding the clinical and molecular complexities of four major types of epithelial ovarian cancer (serous, endometrioid, clear cell, and mucinous). As such, further in depth studies are needed for identification of molecular signalling network complexities associated with effective prognostication and targeted therapies to prevent or treat metastasis. Therefore, understanding the metastatic potential of primary ovarian cancer and therapeutic interventions against lethal ovarian cancer for the development of personalized therapies is very much indispensable. Consequently, in this review we have updated the key dysregulated genes of four major subtypes of epithelial carcinomas. We have also highlighted the recent advances and current challenges in unravelling the complexities of the origin of tumor as well as genetic heterogeneity of ovarian cancer.

The relationship between human muth homolog 1 gene mutation at site 415 and sporadic colon cancers in Chinese Han population

Background: The genetic factors of colon cancer play an important role in the tumor development and growth. The incidence of colon cancers has greatly increased in China. However, few data is available for the relationship between human muth homolog 1 (hMLH1) gene mutation at site 415 and sporadic colon cancers in Chinese population. Objective: Investigate the relationship between G→C mutation in hMLH1 gene at site 415 and sporadic colon cancers in Chinese Han population. Methods: Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, the genotype of the hMLH1 gene was analyzed at site 415 in 97 cases of sporadic colon cancer patients and 138 controls. Reverse-transcription (RT)-PCR was used to determine the level of hMLH1 mRNA expression in normal colonic mucosa of patients with different genotype. Results: The frequency of genotype C/C at the 415 site of the hMLH1 gene was significantly higher in colon cancer patients than in controls. The expression levels of hMLH1 mRNA in normal colonic mucosa were similar in colon cancer patients with different genotypes. Conclusion: G’!C mutation in hMLH1 gene at site 415 may represent a genetic factor that is associated with sporadic colon cancer in a small group of Chinese Han population.

Genetic Variants in Epigenetic Pathways and Risks of Multiple Cancers in the GAME-ON Consortium

Background: Epigenetic disturbances are crucial in cancer initiation, potentially with pleiotropic effects, and may be influenced by the genetic background.Methods: In a subsets (ASSET) meta-analytic approach, we investigated associations of genetic variants related to epigenetic mechanisms with risks of breast, lung, colorectal, ovarian and prostate carcinomas using 51,724 cases and 52,001 controls. False discovery rate-corrected P values (q values < 0.05) were considered statistically significant.Results: Among 162,887 imputed or genotyped variants in 555 candidate genes, SNPs in eight genes were associated with risk of more than one cancer type. For example, variants in BABAM1 were confirmed as a susceptibility locus for squamous cell lung, overall breast, estrogen receptor (ER)-negative breast, and overall prostate, and overall serous ovarian cancer; the most significant variant was rs4808076 [OR = 1.14; 95% confidence interval (CI) = 1.10-1.19; q = 6.87 × 10-5]. DPF1 rs12611084 was inversely associated with ER-negative breast, endometrioid ovarian, and overall and aggressive prostate cancer risk (OR = 0.93; 95% CI = 0.91-0.96; q = 0.005). Variants in L3MBTL3 were associated with colorectal, overall breast, ER-negative breast, clear cell ovarian, and overall and aggressive prostate cancer risk (e.g., rs9388766: OR = 1.06; 95% CI = 1.03-1.08; q = 0.02). Variants in TET2 were significantly associated with overall breast, overall prostate, overall ovarian, and endometrioid ovarian cancer risk, with rs62331150 showing bidirectional effects. Analyses of subpathways did not reveal gene subsets that contributed disproportionately to susceptibility.Conclusions: Functional and correlative studies are now needed to elucidate the potential links between germline genotype, epigenetic function, and cancer etiology.Impact: This approach provides novel insight into possible pleiotropic effects of genes involved in epigenetic processes. Cancer Epidemiol Biomarkers Prev; 26(6); 816-25. ©2017 AACR.

MR Imaging-Pathologic Correlation in Ovarian Cancer

There are many ovarian cancer subtypes, giving rise to a range of appearances at gross pathology and magnetic resonance (MR) imaging. Certain fundamental concepts at MR, arising from underlying tissue characteristics, can provide guidance to radiologists in suggesting a diagnosis. The ability of multiparametric MR to risk stratify ovarian masses can contribute substantially to clinical decision making and patient management.

Lynch Syndrome Screening in the Gynecologic Tract: Current State of the Art

Lynch syndrome underlies approximately 5% of endometrial cancers and ∼1% of ovarian cancers. Gynecologic malignancies are often the presenting cancer in these patients. Therefore, there is considerable benefit to identifying these patients and enrolling them and affected family members in surveillance programs for secondary malignancies. The molecular basis for Lynch syndrome is a defect in the DNA mismatch repair (MMR) system. Tumors can be screened for these defects using immunohistochemistry to identify loss of MMR proteins or by enlisting polymerase chain reaction to identify the microsatellite instability that attends dysfunctional MMR. However, diagnostic confirmation of Lynch syndrome requires germline mutational testing. The algorithm for screening endometrial carcinomas for Lynch syndrome remains a subject of debate, with some studies supporting universal screening and others proposing a hybrid approach informed by clinicopathologic features. This review discusses the rationales and relative merits of current Lynch syndrome-screening approaches for endometrial and ovarian cancers and provides pathologists with an informed approach to Lynch syndrome testing in gynecologic cancers. It also addresses the clinical difficulties presented by cases with discordant screening and germline results (Lynch-like cancers) and emphasizes the critical role of strong communication with clinician and genetic counseling colleagues to ensure that the significance of a positive screening test is appropriately conveyed to patients. Finally, it discusses the need for more nuanced cost-effective analyses and the potential role for next-generation sequencing panels in future screening efforts.

Genetic and molecular changes in ovarian cancer

Epithelial ovarian cancer represents the most lethal gynecological malignancy in the developed world, and can be divided into five main histological subtypes: high grade serous, endometrioid, clear cell, mucinous and low grade serous. These subtypes represent distinct disease entities, both clinically and at the molecular level. Molecular analysis has revealed significant genetic heterogeneity in ovarian cancer, particularly within the high grade serous subtype. As such, this subtype has been the focus of much research effort to date, revealing molecular subgroups at both the genomic and transcriptomic level that have clinical implications. However, stratification of ovarian cancer patients based on the underlying biology of their disease remains in its infancy. Here, we summarize the molecular changes that characterize the five main ovarian cancer subtypes, highlight potential opportunities for targeted therapeutic intervention and outline priorities for future research.

Significant frequency of MSH2/MSH6 abnormality in ovarian endometrioid carcinoma supports histotype-specific Lynch syndrome screening in ovarian carcinomas

AIMS

Lynch syndrome screening in ovarian carcinoma is controversial. The aim of this study was to assess the frequency of deficient mismatch repair (dMMR) protein in a retrospective cohort enriched for non-high-grade serous carcinomas and its association with outcome within histological types.

METHODS AND RESULTS

Tissue microarrays representing 612 ovarian carcinomas were tested for mismatch repair proteins (MLH1, PMS2, MSH2, and MSH6) by immunohistochemistry. dMMR was detected in 13.8% of endometrioid and 2.4% of clear cell carcinomas, but not in other histological types. Within endometrioid carcinomas, 11 of 25 dMMR cases showed abnormal MLH1/PMS2, 10 cases showed abnormal MSH2/MSH6, and four cases showed only abnormal MSH6, indicating that at least 7.7% of endometrioid carcinomas have dMMR probably related to Lynch syndrome. The four dMMR clear cell carcinomas showed abnormal MSH2/MSH6 in three cases and only abnormal MSH6 in one case, all probably related to Lynch syndrome. Within endometrioid carcinomas, dMMR was significantly associated with age <50 years, synchronous endometrial endometrioid carcinoma, a higher CA125 level at diagnosis, higher FIGO grade, absence of ARID1A, and at least 20 CD8-positive intraepithelial lymphocytes per high-power field, but was not associated with cancer-specific death. Age <50 years, higher CA125 levels at diagnosis and at least 20 CD8-positive intraepithelial lymphocytes per high-power field remained significant after adjustment for multiple testing, but their sensitivity for identifying dMMR remained insufficient.

CONCLUSION

Our data support the policy of histotype-specific Lynch syndrome screening in ovarian carcinoma confined to endometrioid and clear cell carcinomas.

Hereditary ovarian cancer: not only BRCA 1 and 2 genes

More than one-fifth of ovarian tumors have hereditary susceptibility and, in about 65-85% of these cases, the genetic abnormality is a germline mutation in BRCA genes. Nevertheless, several other suppressor genes and oncogenes have been associated with hereditary ovarian cancers, including the mismatch repair (MMR) genes in Lynch syndrome, the tumor suppressor gene, TP53, in the Li-Fraumeni syndrome, and several other genes involved in the double-strand breaks repair system, such as CHEK2, RAD51, BRIP1, and PALB2. The study of genetic discriminators and deregulated pathways involved in hereditary ovarian syndromes is relevant for the future development of molecular diagnostic strategies and targeted therapeutic approaches. The recent development and implementation of next-generation sequencing technologies have provided the opportunity to simultaneously analyze multiple cancer susceptibility genes, reduce the delay and costs, and optimize the molecular diagnosis of hereditary tumors. Particularly, the identification of mutations in ovarian cancer susceptibility genes in healthy women may result in a more personalized cancer risk management with tailored clinical and radiological surveillance, chemopreventive approaches, and/or prophylactic surgeries. On the other hand, for ovarian cancer patients, the identification of mutations may provide potential targets for biologic agents and guide treatment decision-making.

Novel insights on the malignant transformation of endometriosis into ovarian carcinoma

The malignant transformation of endometriosis is an uncommon event, which happens in 0.7-2.5% of the cases, and, when occurs, it usually involves the ovary. A 2 to 3-fold higher risk of ovarian endometrioid and clear cell carcinoma has been reported in women with endometriosis. Pathological studies have detected a morphological continuum of sequential steps from normal endometriotic cyst epithelium to atypical endometriosis and finally to invasive carcinoma. Ovarian endometrioid carcinoma harbors mutations of CTNNB1 in 16-53.3%, of PTEN in 14-20% and of ARID1A in 30-55% of the cases. Ovarian clear cell carcinoma harbors mutations of PIK3CA in 20-40% and of ARID1 in 15-75% of the cases. Whereas estrogen receptors and progesterone receptors are quite always absent, HNF-1b is often over-expressed in this histotype. Atypical endometriosis and endometriosis-related ovarian neoplasms share molecular alterations, such as PTEN mutations, ARID1A mutations and up-regulation of HNF-1b. Moreover, ARID1A mutations have been noted in clear cell tumors and contiguous atypical endometriosis, but not in distant endometriotic lesions. The loss of BAF250a protein expression is suggestive for the presence of ARID1A mutations, and represents an useful marker of malignant transformation of endometriosis.

Lynch Syndrome in patients with clear cell and endometrioid cancers of the ovary

OBJECTIVE

Patients with Lynch Syndrome are at an increased risk for a variety of malignancies, including ovarian cancer. Ovarian cancers associated with Lynch Syndrome are predominantly clear cell or endometrioid in histology. Lynch Syndrome is characterized by germline mutations in mismatch repair (MMR) genes. The current study aims to assess the prevalence of loss of MMR expression in patients with endometrioid and clear cell ovarian carcinoma.

METHODS

A retrospective review identified 90 patients with endometrioid and/or clear cell carcinomas. Slides made from tumor tissue microarray blocks were evaluated using immunohistochemical stains with antibodies against MLH1, PMS2, MSH2, and MSH6. Statistical analysis was performed.

RESULTS

Seven of the 90 cases (7.8%) had loss of MMR expression. The mean age of patients with loss of MMR expression (47 years) was significantly younger than those with retained MMR expression (p=0.014). Loss of MMR expression was present in 20% of patients under the age of 53 with clear cell or endometrioid cancers. Genetic studies found that 3 of the 5 patients with loss of MMR expression carried mutations consistent with Lynch Syndrome; acquired hypermethylation of MLH1 was noted in one patient. Six of 7 patients (86%) whose tumors lacked MMR expression had synchronous or metachronous primary malignancies, a significantly greater prevalence than those with retained MMR expression (p<0.001).

CONCLUSION

Patients under the age of 53 with clear cell or endometrioid ovarian carcinomas are at a clinically significant risk for loss of MMR expression and Lynch Syndrome; routine screening with immunohistochemical staining should be considered.

Lynch syndrome-associated neoplasms: a discussion on histopathology and immunohistochemistry

It was a century ago that Warthin, a pathologist, first described the clinical condition now known as Lynch syndrome. One hundred years later, our understanding of this syndrome has advanced significantly. Much of the progress took place over the last 25 years and was marked by a series of interacting developments from the disciplines of clinical oncology, pathology, and molecular genetics, with each development serving to guide or enhance the next. The advancement of our understanding about the pathology of Lynch syndrome associated tumors exemplifies such intimate interplay among disciplines. Today, accumulative knowledge has enabled surgical pathologists to detect tumors that are likely to be associated with Lynch syndrome, and the pathologist is playing an increasingly more important role in the care of these patients. The pathologist's ability is afforded primarily by information gained from tumor histopathology and by DNA mismatch repair protein immunohistochemistry. It is therefore pertinent both for the pathologists to accurately ascertain this morphologic information, and for all that are involved in the care of these patients to thoroughly understand the implications of such information. This article provides an overview of the development of histopathology and immunohistochemistry in Lynch syndrome-associated tumors, particularly in colorectal and endometrial cancers, and outlines the issues and current status of these specific pathologic aspects in not only the major tumors but also those less commonly seen or only newly reported in Lynch syndrome patients.

Association between IHC and MSI testing to identify mismatch repair-deficient patients with ovarian cancer

OBJECTIVE

In epithelial ovarian cancer, concordance between results of microsatellite instability (MSI) and immunohistochemical (IHC) testing has not been demonstrated. This study evaluated the association of MSI-high (MSI-H) status with loss of expression (LoE) of mismatch repair (MMR) proteins on IHC and assessed for potential factors affecting the strength of the association.

METHODS

Tumor specimens from three population-based studies of epithelial ovarian cancer were stained for MMR proteins through manual or automated methods, and results were interpreted by one of two pathologists. Tumor and germline DNA was extracted and MSI testing performed. Multivariable logistic regression models were fitted to predict loss of IHC expression based on MSI status after adjusting for staining method and reading pathologist.

RESULTS

Of 834 cases, 564 (67.6%) were concordant; 41 were classified as MSI-H with LoE and 523 as microsatellite stable (MSS) with no LoE. Of the 270 discordant cases, 83 were MSI-H with no LoE and 187 were MSS with LoE. Both IHC staining method and reading pathologist were strongly associated with discordant results.

CONCLUSIONS

Lack of concordance in the current study may be related to inconsistencies in IHC testing methods and interpretation. Results support the need for validation studies before routine screening of ovarian tumors is implemented in clinical practice for the purpose of identifying Lynch syndrome.

Evaluating cell lines as tumour models by comparison of genomic profiles

Cancer cell lines are frequently used as in vitro tumour models. Recent molecular profiles of hundreds of cell lines from The Cancer Cell Line Encyclopedia and thousands of tumour samples from the Cancer Genome Atlas now allow a systematic genomic comparison of cell lines and tumours. Here we analyse a panel of 47 ovarian cancer cell lines and identify those that have the highest genetic similarity to ovarian tumours. Our comparison of copy-number changes, mutations and mRNA expression profiles reveals pronounced differences in molecular profiles between commonly used ovarian cancer cell lines and high-grade serous ovarian cancer tumour samples. We identify several rarely used cell lines that more closely resemble cognate tumour profiles than commonly used cell lines, and we propose these lines as the most suitable models of ovarian cancer. Our results indicate that the gap between cell lines and tumours can be bridged by genomically informed choices of cell line models for all tumour types.

Cell lines are widely used in cancer research to study tumour biology. Here Domcke et al. compare genomic data from ovarian cancer cell lines with those from clinical ovarian tumour samples and identify cell lines that most closely resemble the genomic features of high-grade serous ovarian cancer.

Differentially methylated loci distinguish ovarian carcinoma histological types: evaluation of a DNA methylation assay in FFPE tissue

Epigenomic markers can identify tumor subtypes, but few platforms can accommodate formalin-fixed paraffin-embedded (FFPE) tumor tissue. We tested different amounts of bisulfite-converted (bs) DNA from six FFPE ovarian carcinomas (OC) of serous, endometrioid, and clear cell histologies and two HapMap constitutional genomes to evaluate the performance of the GoldenGate methylation assay. Methylation status at each 1,505 CpG site was expressed as β-values. Comparing 400 ng versus 250 ng bsDNA, reproducibility of the assay ranged from Spearman r² = 0.41 to 0.90, indicating that β-values obtained with a lower DNA amount did not always correlate well with the higher amount. Average methylation for the six samples was higher using 250 ng (β-value = 0.45, SD = 0.29) than with 400 ng (β-value = 0.36, SD = 0.32). Reproducibility between duplicate HapMap samples (r² = 0.76 to 0.92) was also variable. Using 400 ng input bsDNA, THBS2 and ERG were differentially methylated across all histologic types and between endometrioid and clear cell types at <0.1% false discovery rate. Methylation did not always correlate with gene expression (r² = −0.70 to 0.15). We found that lower bsDNA overestimates methylation, and, using higher bsDNA amounts, we confirmed a previous report of higher methylation of THBS2 in clear cell OC, which could provide new insight into biological pathways that distinguish OC histological types.

Type-specific cell line models for type-specific ovarian cancer research

BACKGROUND

OVARIAN CARCINOMAS CONSIST OF AT LEAST FIVE DISTINCT DISEASES: high-grade serous, low-grade serous, clear cell, endometrioid, and mucinous. Biomarker and molecular characterization may represent a more biologically relevant basis for grouping and treating this family of tumors, rather than site of origin. Molecular characteristics have become the new standard for clinical pathology, however development of tailored type-specific therapies is hampered by a failure of basic research to recognize that model systems used to study these diseases must also be stratified. Unrelated model systems do offer value for study of biochemical processes but specific cellular context needs to be applied to assess relevant therapeutic strategies.

METHODS

We have focused on the identification of clear cell carcinoma cell line models. A panel of 32 "ovarian cancer" cell lines has been classified into histotypes using a combination of mutation profiles, IHC mutation-surrogates, and a validated immunohistochemical model. All cell lines were identity verified using STR analysis.

RESULTS

Many described ovarian clear cell lines have characteristic mutations (including ARID1A and PIK3CA) and an overall molecular/immuno-profile typical of primary tumors. Mutations in TP53 were present in the majority of high-grade serous cell lines. Advanced genomic analysis of bona-fide clear cell carcinoma cell lines also support copy number changes in typical biomarkers such at MET and HNF1B and a lack of any recurrent expressed re-arrangements.

CONCLUSIONS

As with primary ovarian tumors, mutation status of cancer genes like ARID1A and TP53 and a general immuno-profile serve well for establishing histotype of ovarian cancer cell We describe specific biomarkers and molecular features to re-classify generic "ovarian carcinoma" cell lines into type specific categories. Our data supports the use of prototype clear cell lines, such as TOV21G and JHOC-5, and questions the use of SKOV3 and A2780 as models of high-grade serous carcinoma.

Pathogenesis and the role of ARID1A mutation in endometriosis-related ovarian neoplasms

Endometriosis-related ovarian neoplasms (ERONs) are a unique group of tumors as they are associated with endometriosis, especially endometriosis presenting as an ovarian endometriotic cyst (endometrioma). ERONs include clear cell carcinoma, endometrioid carcinoma, and seromucinous borderline tumor. A growing body of evidence from both clinicopathologic and molecular studies suggests that most, if not all, ERONs develop from endometriotic cyst epithelium through different stages of tumor progression. The endometriotic cyst contains abundant iron-induced reactive oxygen species that are thought to be mutagenic, and chronic exposure of cystic epithelium to this microenvironment facilitates the accumulation of somatic mutations that ultimately result in tumor development. Molecular analyses of ERONs, including genome-wide screens, have identified several molecular genetic alterations that lead to aberrant activation or inactivation of pathways involving ARID1A, PI3K, Wnt, and PP2A. Among all molecular genetic changes identified to date, inactivating mutations of the ARID1A tumor suppressor gene are the most common in ERON. Understanding the molecular changes and pathogenesis involved in the development of ERON is fundamental for future translational studies aimed at designing new diagnostic tests for early detection and identifying critical molecular features for targeted therapeutics.

DNA damage and repair in epithelium after allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) in humans, following hematoablative treatment, results in biological chimeras. In this case, the transplanted hematopoietic, immune cells and their derivatives can be considered the donor genotype, while the other tissues are the recipient genotype. The first sequel, which has been recognized in the development of chimerical organisms after allo-HSCT, is the graft versus host (GvH) reaction, in which the new developed immune cells from the graft recognize the host’s epithelial cells as foreign and mount an inflammatory response to kill them. There is now accumulating evidence that this chronic inflammatory tissue stress may contribute to clinical consequences in the transplant recipient. It has been recently reported that host epithelial tissue acquire genomic alterations and display a mutator phenotype that may be linked to the occurrence of a GvH reaction. The current review discusses existing data on this recently discovered phenomenon and focuses on the possible pathogenesis, clinical significance and therapeutic implications.

The role of tandem duplicator phenotype in tumour evolution in high-grade serous ovarian cancer

High-grade serous ovarian carcinoma (HGSOC) is characterized by genomic instability, ubiquitous TP53 loss, and frequent development of platinum resistance. Loss of homologous recombination (HR) is a mutator phenotype present in 50% of HGSOCs and confers hypersensitivity to platinum treatment. We asked which other mutator phenotypes are present in HGSOC and how they drive the emergence of platinum resistance. We performed whole-genome paired-end sequencing on a model of two HGSOC cases, each consisting of a pair of cell lines established before and after clinical resistance emerged, to describe their structural variants (SVs) and to infer their ancestral genomes as the SVs present within each pair. The first case (PEO1/PEO4), with HR deficiency, acquired translocations and small deletions through its early evolution, but a revertant BRCA2 mutation restoring HR function in the resistant lineage re-stabilized its genome and reduced platinum sensitivity. The second case (PEO14/PEO23) had 216 tandem duplications and did not show evidence of HR or mismatch repair deficiency. By comparing the cell lines to the tissues from which they originated, we showed that the tandem duplicator mutator phenotype arose early in progression in vivo and persisted throughout evolution in vivo and in vitro, which may have enabled continual evolution. From the analysis of SNP array data from 454 HGSOC cases in The Cancer Genome Atlas series, we estimate that 12.8% of cases show patterns of aberrations similar to the tandem duplicator, and this phenotype is mutually exclusive with BRCA1/2 carrier mutations.

Ovarian endometrioid adenocarcinoma: incidence and clinical significance of the morphologic and immunohistochemical markers of mismatch repair protein defects and tumor microsatellite instability

A subset of women with uterine cancer exhibiting defective mismatch repair (MMR) proteins and microsatellite instability (MSI) may have Lynch syndrome, which also confers a risk for colorectal cancer and other cancers in the patient and in her family. Screening algorithms based on clinical and pathologic criteria are effective in determining which patients with uterine cancer are most likely to benefit from definitive genetic testing for Lynch syndrome. Ovarian cancer, particularly endometrioid adenocarcinoma, is also associated with Lynch syndrome, although the risk is much smaller than for uterine cancer. This study evaluated whether the morphologic criteria [tumor-infiltrating lymphocytes (TILs), peritumoral lymphocytes (PTLs), dedifferentiated morphology)] currently used to screen uterine cancer for further Lynch syndrome testing can be applied to ovarian cancer. Among 71 patients with pure ovarian endometrioid adenocarcinoma treated at a single institution, 13% had a tumor with TILs, 3% had PTLs, and none had dedifferentiated morphology. Overall, 10% of tumors had abnormal MMR protein status, defined as complete immunohistochemical loss of expression of MLH1, MSH2, MSH6, and/or PMS2. Each of these tumors with abnormal MMR status demonstrated MSI using a polymerase chain reaction-based assay evaluating 5 mononucleotide repeat markers. No relationship was found between patient age, TILs, PTLs, or a spectrum of other morphologic variables and MMR protein status/MSI. Only 1/7 tumors with abnormal MMR/MSI had TILs/PTLs. Among 14 patients who died, 12 (86%) had normal MMR status. Among 7 patients with tumors with abnormal MMR/MSI, 5 (71%) were alive without disease. Concurrent uterine tumor was present in 5/7 patients whose ovarian tumor had abnormal MMR/MSI. This study suggests that the morphologic criteria used to screen patients with uterine cancer for further Lynch syndrome testing are not applicable in patients with ovarian cancer. Although abnormal MMR/MSI did not carry prognostic value in this study, it did predict the involvement of the uterus by the tumor. Thus, in patients with ovarian endometrioid adenocarcinoma who undergo uterus-sparing surgery, abnormal MMR/MSI should prompt further diagnostic evaluation of the endometrium for tumor.

Frequency of mismatch repair deficiency in ovarian cancer: a systematic review This article is a US Government work and, as such, is in the public domain of the United States of America

Loss of mismatch repair (MMR) capacity may represent an important tumor initiating mechanism in ovarian cancer. We conducted a systematic review to analyze the frequency of microsatellite instability (MSI), immunohistochemical (IHC) staining for MMR proteins, and hypermethylation of the MLH1 promoter region in ovarian cancers. Studies examining MSI, loss of MMR gene expression by IHC staining and MLH1 promoter hypermethylation in ovarian cancer were identified by a systematic literature search of the PubMed electronic database through August 31, 2009. Pertinent data was extracted from eligible studies and estimates for pooled proportions were computed using random effects models. The pooled proportion of MSI detection was 0.10 (95% CI, 0.06-0.14) among 1,234 cases in 22 studies. Dinonucleotide markers had a higher frequency of instability than mononucleotide markers. The pooled proportion of MLH1 or MSH2 staining loss was 0.06 (95% CI, 0.01-0.17) among 474 cases in three studies, with a higher frequency of loss in MLH1. The pooled proportion of MLH1 methylation was 0.10 (95% CI, 0.06-0.15) among 672 cases in seven studies. Data reporting MSI and loss of MMR staining in the same cases was limited. Although MMR deficiency was found in all histologic subtypes, endometrioid cancers had the highest proportion. Approximately 10% of unselected ovarian cancers are related to MMR deficiency. While MMR deficiency is associated with improved survival in other MMR-deficiency related cancer sites, epidemiological and clinical factors related to the MMR-deficient phenotype have not been adequately studied in ovarian cancer to date.

Inactivation of O⁶-methyguanine-DNA methyltransferase by promoter hypermethylation: association of epithelial ovarian carcinogenesis in specific histological types

AIM

The aim of this study was to evaluate O⁶-methyguanine-DNA methyltransferase (MGMT) promoter hypermethylation, MGMT expression and microsatellite instability (MSI), as well as to elucidate their correlation with clinical and pathological parameters in epithelial ovarian cancer.

METHODS

Ovarian cancer tissue specimens (n = 86) were obtained after a staging operation. The MGMT gene was investigated by methylation-specific polymerase chain reaction (MSP) and MGMT expression status was analyzed using immunohistochemistry. MSI status was examined by the fluorescence-based PCR using five National Cancer Institute markers.

RESULTS

Negative MGMT expression was detected in 12 of 86 (14.0%) epithelial ovarian cancers. In 34 cases where MSP results were available, MGMT promoter hypermethylation was detected in five cases (14.7%) with mucinous or clear cell carcinomas, but not in any of other histological types (P = 0.031). Five out of six cases with negative MGMT expression showed MGMT promoter hypermethylation, whereas all of the 28 cases that retained expression of MGMT were unmethylated at the MGMT CpG island (P < 0.001). In 41 cases of MSI results available, seven (17.1%) cases showed MSI-H-phenotyped. Both MGMT promoter hypermethylation and negative MGMT expression were noted only in cases of mucinous or clear cell carcinoma in which MSI status were mostly MSS-phenotyped; however, no significant correlation was found between MSI status and clinicopathological parameters.

CONCLUSIONS

Negative MGMT expression was significantly correlated with MGMT promoter hypermethylation in MSS-phenotyped tumors of mucinous or clear cell carcinoma. The results suggest that MGMT promoter hypermethylation might be associated with epithelial ovarian carcinogenesis in specific histological types.

Molecular Pathology of Ovarian Carcinomas

This content presents a review of molecular pathology of ovarian cancer. The authors present key molecular features for high-grade and low-grade serous carcinomas, endometrioid carcinomas, clear cell carcinomas, and mucinous carcinomas. Cell lineage, mutation and gene expression, pathway alterations, risk factors, prognostic markers, and treatment targets are discussed.

Tumor spreading to the contralateral ovary in bilateral ovarian carcinoma is a late event in clonal evolution

Cancer of the ovary is bilateral in 25%. Cytogenetic analysis could determine whether the disease in bilateral cases is metastatic or two separately occurring primary tumors, but karyotypic information comparing the two cancerous ovaries is limited to a single report with 11 informative cases. We present a series of 32 bilateral ovarian carcinoma cases, analyzed by karyotyping and high-resolution CGH. Our karyotypic findings showed that spreading to the contralateral ovary had occurred in bilateral ovarian cancer cases and that it was a late event in the clonal evolution of the tumors. This was confirmed by the large number of similar changes detected by HR-CGH in the different lesions from the same patient. The chromosomal bands most frequently involved in structural rearrangements were 19p13 (n = 12) and 19q13 (n = 11). The chromosomal bands most frequently gained by both tumorous ovaries were 5p14 (70%), 8q23-24 (65%), 1q23-24 (57%), and 12p12 (48%), whereas the most frequently lost bands were 17p11 (78%), 17p13 (74%), 17p12 (70%), 22q13 (61%), 8p21 and 19q13 (52%), and 8p22-23 (48%). This is the first time that 5p14 is seen gained at such a high frequency in cancer of the ovary; possibly oncogene(s) involved in bilateral ovarian carcinogenesis or tumor progression may reside in this band.

Ovarian cancer

Ovarian carcinomas are a heterogeneous group of neoplasms and are traditionally subclassified based on type and degree of differentiation. Although current clinical management of ovarian carcinoma largely fails to take this heterogeneity into account, it is becoming evident that each major histological type has characteristic genetic defects that deregulate specific signaling pathways in the tumor cells. Moreover, within the most common histological types, the molecular pathogenesis of low-grade versus high-grade tumors appears to be largely distinct. Mouse models of ovarian carcinoma have been developed that recapitulate many of the morphological features, biological behavior, and gene-expression patterns of selected subtypes of ovarian cancer. Such models will likely prove useful for studying ovarian cancer biology and for preclinical testing of molecularly targeted therapeutics, which may ultimately lead to better clinical outcomes for women with ovarian cancer.

Hereditary ovarian carcinoma: heterogeneity, molecular genetics, pathology, and management

Hereditary ovarian cancer accounts for at least 5% of the estimated 22,000 new cases of this disease during 2009. During this same time, over 15,000 will die from malignancy ascribed to ovarian origin. The bulk of these hereditary cases fits the hereditary breast-ovarian cancer syndrome, while virtually all of the remainder will be consonant with the Lynch syndrome, disorders which are autosomal dominantly inherited. Advances in molecular genetics have led to the identification of BRCA1 and BRCA2 gene mutations which predispose to the hereditary breast-ovarian cancer syndrome, and mutations in mismatch repair genes, the most common of which are MSH2 and MLH1, which predispose to Lynch syndrome. These discoveries enable relatively certain diagnosis, limited only by their variable penetrance, so that identification of mutation carriers through a comprehensive cancer family history might be possible. This paper reviews the subject of hereditary ovarian cancer, with particular attention to its molecular genetic basis, its pathology, and its phenotypic/genotypic heterogeneity.

A review of the clinical relevance of mismatch-repair deficiency in ovarian cancer

Ovarian cancer ranks fifth in both cancer incidence and mortality among women in the United States. Defects in the mismatch-repair (MMR) pathway that arise through genetic and/or epigenetic mechanisms may be important etiologically in a reasonable proportion of ovarian cancers. Genetic mechanisms of MMR dysfunction include germline and somatic mutations in the MMR proteins. Germline mutations cause hereditary nonpolyposis colorectal cancer (HNPCC), which is the third most common cause of inherited ovarian cancer after BRCA1 and BRCA2 mutations. An epigenetic mechanism known to cause inactivation of the MMR system is promoter hypermethylation of 1 of the MMR genes, mutL homolog 1 (MLH1). Various laboratory methods, in addition to clinical and histopathologic criteria, can be used to identify MMR-deficient ovarian cancers. Such methods include microsatellite instability analysis, immunohistochemistry, MLH1 promoter hypermethylation testing, and germline mutation analysis. In this review, the authors describe the existing literature regarding the molecular, clinical, and histologic characteristics of MMR-deficient ovarian cancers along with the possible effect on survival and treatment response. By further defining the profile of MMR-deficient ovarian cancers and their associated etiologic mechanisms, there may be a greater potential to distinguish between those of hereditary and sporadic etiology. The ability to make such distinctions may be of diagnostic, prognostic, and therapeutic utility.

Ovarian cancer at young age: the contribution of mismatch-repair defects in a population-based series of epithelial ovarian cancer before age 40

At least one of ten patients with ovarian cancer is estimated to develop their tumor because of heredity with the breast and ovarian cancer syndrome due to mutations in the BRCA1 and BRCA2 genes and hereditary nonpolyposis colorectal cancer (HNPCC) being the major genetic causes. Cancer at young age is a hallmark of heredity, and ovarian cancers associated with HNPCC have been demonstrated to develop at a particularly early age. We used the Swedish Cancer Registry to identify a population-based series of 98 invasive epithelial ovarian cancers that developed before 40 years. Mucinous and endometrioid cancers were overrepresented and were diagnosed in 27% and 16% of the tumors, respectively. Immunostaining using antibodies against MLH1, PMS2, MSH2, and MSH6 was used to assess the mismatch-repair status and revealed loss of expression of MLH1/PMS2 in two cases, loss of MSH2/MSH6 in one case, and loss of MSH6 only in three tumors. A microsatellite instability-high phenotype was verified in five of six tumors. Based on the identified mutations and family history of cancer, several of these individuals are likely to be affected by HNPCC. We conclude that although the causes of the vast majority of epithelial ovarian cancer at young age are unknown, HNPCC should be considered because of the high risk of metachronous colorectal cancer in the individual and the possibility of preventing additional cancers in the family through control programs.

Immunohistochemical staining of hMLH1 and hMSH2 reflects microsatellite instability status in ovarian carcinoma

Microsatellite instability is due to defects in the family of DNA repair genes, primarily hMLH1 and hMSH2, which can be detected by immunohistochemical staining. However, it is unclear whether immunohistochemical staining can accurately predict microsatellite instability status. We sought here to evaluate the sensitivity, specificity, and predictive values of immunostaining for the expression of the DNA mismatch-repair genes hMLH1 or hMSH2 in predicting microsatellite instability in ovarian carcinoma. Tissue microarrays with specimens from 322 women with primary ovarian carcinoma were stained with antibodies to hMLH1 and hMSH2; cases in which either hMLH1 or hMSH2 were negative were analyzed for microsatellite instability with the five-marker panel recommended by the National Cancer Institute (BAT26, BAT25, D5S346, D2S123, and D17S250). Microsatellite instability was also analyzed in another 19 cases selected at random in which both hMLH1 and hMSH2 were positive. Tumors with instability at two or more of the five NCI markers were considered to have a high level of microsatellite instability; tumors showing instability at only one marker were considered microsatellite instability-low; and tumors in which no markers exhibited microsatellite instability were considered microsatellite stable. We found that negative staining for hMLH1 protein (five cases) or hMSH2 protein (two cases) was associated with high level of microsatellite instability. The sensitivity and specificity of immunohistochemical staining for hMLH1 were 62 and 100% and those of hMSH2 alone were 25 and 100%. Combining loss of expression of both hMLH1 and hMSH2 led to sensitivity, specificity, and positive and negative predictive values of 87, 100, 100, and 95%. These results suggest that use of a two-molecule panel (hMLH1 and hMSH2) can accurately determine the microsatellite instability status of patients with ovarian cancer.

Mismatch repair and treatment resistance in ovarian cancer

BACKGROUND

The treatment of ovarian cancer is hindered by intrinsic or acquired resistance to platinum-based chemotherapy. The aim of this study is to determine the frequency of mismatch repair (MMR) inactivation in ovarian cancer and its association with resistance to platinum-based chemotherapy.

METHODS

We determined, microsatellite instability (MSI) as a marker for MMR inactivation (analysis of BAT25 and BAT26), MLH1 promoter methylation status (methylation specific PCR on bisulfite treated DNA) and mRNA expression of MLH1, MSH2, MSH3, MSH6 and PMS2 (quantitative RT-PCR) in 75 ovarian carcinomas and eight ovarian cancer cell lines

RESULTS

MSI was detected in three of the eight cell lines i.e. A2780 (no MLH1 mRNA expression due to promoter methylation), SKOV3 (no MLH1 mRNA expression) and 2774 (no altered expression of MMR genes). Overall, there was no association between cisplatin response and MMR status in these eight cell lines. Seven of the 75 ovarian carcinomas showed MLH1 promoter methylation, however, none of these showed MSI. Forty-six of these patients received platinum-based chemotherapy (11 non-responders, 34 responders, one unknown response). The resistance seen in the eleven non-responders was not related to MSI and therefore also not to MMR inactivation.

CONCLUSION

No MMR inactivation was detected in 75 ovarian carcinoma specimens and no association was seen between MMR inactivation and resistance in the ovarian cancer cell lines as well as the ovarian carcinomas. In the discussion, the results were compared to that of twenty similar studies in the literature including in total 1315 ovarian cancer patients. Although no association between response and MMR status was seen in the primary tumor the possible role of MMR inactivation in acquired resistance deserves further investigation.

Discordant genetic changes in ovarian and endometrial endometrioid carcinomas: a potential pitfall in molecular diagnosis

Endometrioid carcinoma simultaneously involving ovaries as well as the uterine corpus may present a diagnostic dilemma because of the difficulty in determining whether the lesions are separate primary tumors or metastases. It has been reported that the detection of clonality using microsatellite markers may be useful in solving this dilemma. To determine the usefulness of this technique, we compared the genetic alterations in microsatellite markers present in matched pairs of ovarian tumors from 12 patients. The study includes four ovarian cancer FIGO stage I and eight stage III/IV patients, and four patients also with independent endometrial carcinoma of the uterus. DNA from paraffin-embedded tissue was extracted and amplified using a multiplex polymerase chain reaction, after which the status of microsatellite instability and loss of heterozygosity in four microsatellite loci (BAT25, BAT26, D17S250, and D5S346) were determined. In the four patients with stage I ovarian cancer, four microsatellite markers were identical in one patient and three were identical in the remaining three patients. In high-stage patients, three markers were identical in at least 4/8 cases. In three of four patients with uterine involvement, three of the four markers were identical in the uterine tumor and one of the corresponding ovarian tumors. These results suggest that genetic discordance does not indicate independent origin or metastasis of the tumor but instead a progression of genetic changes at separate sites probably due to the marked genetic instability existing in these tumors. Because of these discordant genetic changes, great caution should be taken when distinguishing between primary and metastatic tumors on the basis of microsatellite markers.