Microsatellite instability in ovarian neoplasms

Spectrum of Germ Cell Tumor (GCT): 5 Years' Experience in a Tertiary Care Center and Utility of OCT4 as a Diagnostic Adjunct

Germ cell tumors (GCT) are an intriguing group of neoplasm having myriad clinical and morphological presentation. More and more transcription factors are being evaluated for identification of same. To study the spectrum of GCTs in a tertiary care center and the use of a stem cell marker OCT4 as a diagnostic adjunct, a retrospective 5-year (2008-2013) study was carried out. Immunohistochemistry (IHC) with OCT4 was performed on all cases and IHC for α feto protein (AFP), CD30, and epithelial membrane antigen (EMA) as per requirement. Cohort included 73 cases (23 males and 50 females). Testicular and ovarian GCTs accounted for 95.83% and 35.71% respectively. In males, seminoma was the commonest (34.78%) followed by mixed GCT (26%). 17.85% of ovarian GCTs were malignant mostly constituted by dysgerminoma (18%). Benign mature cystic teratoma (MCT) constituted 50% of ovarian GCTs. OCT4 immunoexpression was seen in all cases of seminoma/dysgerminoma, embryonal carcinoma, immature teratoma, and seminomatous/embryomatous component of mixed GCTs. Pure yolk sac tumor (YST) and MCT were consistently negative. OCT4 was especially helpful in identification of mixed GCT. A panel of immunohistochemical markers would be a more ideal way to identify and clarify the components because correct identification of the components is important for therapeutic intervention and prognostication. OCT4 being a primordial germ cell marker predicts aggressive behavior and targeted therapy against this should be investigated.

A COEUR cohort study of SATB2 expression and its prognostic value in ovarian endometrioid carcinoma

The aim of this study was to describe the expression of special AT-rich sequence-binding protein 2 (SATB2) in ovarian endometrioid carcinoma (EC). SATB2 is a nuclear matrix-associated transcription factor that is associated with abnormal expression in certain cancers but has not been reported for ovarian carcinoma. SATB2 mRNA and protein expression was first assessed in a pilot cohort of 26 samples by Affymetrix microarray and by routine immunohistochemistry on a small tissue microarray. A large multicenter validation cohort representing the well-characterized cases of 235 ovarian EC from the Canadian Ovarian Experimental Unified Resource (COEUR) was then used to validate this result and to assess the prognostic impact of SATB2 expression. SATB2 staining was scored as negative, weak, moderate, and strong intensity, and by percentage of stained cells. No SATB2 expression was observed in clear cell carcinomas but 10% (n = 3) of the ECs in the pilot cohort showed SATB2 expression. In the validation cohort, strong expression was observed in 11% of ECs, while weak or moderate expression levels were detected in 12% of cases. Evaluation of SATB2 expression with clinicopathological parameters revealed an association with patient age and Federation International of Gynecology and Obstetrics grade but not with disease stage or postoperative residual disease. Any expression of SATB2, independent of intensity, was also associated with longer survival and improved progression-free survival with hazard ratio (HR) = 0.14 (95% CI 0.03-0.56) and HR = 0.16 (95% CI 0.02-1.24) respectively. A greater beneficial effect was observed in patients with stage III/IV disease compared to patients with stage I/II disease. Furthermore, direct comparison of SATB2 with other reported prognostic biomarkers such as progesterone receptor, CDX2 and β-catenin within this cohort showed that SATB2 had the strongest association with survival. Given the current lack of accurate prognostic factors for these patients, SATB2 has promising clinical utility and warrants further study.

Risk factors for ovarian cancers with and without microsatellite instability

OBJECTIVE

In a population-based sample of epithelial ovarian cancers, the objective of this study was to evaluate the association between microsatellite instability (MSI) status and the following factors: (1) ovarian cancer risk factors and (2) the distribution of the specific histologic subtypes.

PATIENTS AND METHODS

Participants were drawn from 3 population-based studies of primary epithelial ovarian cancer; tumor DNA was analyzed using 5 standardized microsatellite markers to assess the MSI status. Patients were divided into 3 groups (MSI-high, MSI-low, and MSI-stable) according to the National Cancer Institute criteria. We compared the prevalence of specific known risk and protective factors among the 3 subgroups, including body mass index, smoking history, parity, BRCA1 and BRCA2 mutation status, past oral contraceptive use, and tubal ligation. Similarly, we compared the distribution of the histologic subtypes among the 3 subgroups.

RESULTS

A total of 917 ovarian cancer patients were included. One hundred twenty-seven cases of cancer (13.8%) were MSI-high. Subgroup analyses according to smoking, body mass index, parity, past oral contraceptive use, and past tubal ligation did not reveal any statistically significance differences among the groups. Among the 29 patients with BRCA1 mutations, 20.7% had MSI-high cancers compared with 5.9% among 17 patients with BRCA2 mutations. The proportions of different ovarian cancer histologies among the various MSI subgroups were similar.

CONCLUSIONS

The prevalence of risk and protective factors among ovarian cancer patients is similar for cancers with and without MSI. The distributions of MSI do not differ significantly among ovarian cancers with different histologies. Ovarian cancer patients with BRCA1 mutations had a 21% rate of MSI-high tumors compared with 6% among patients with BRCA2 mutations, but this difference was not statistically significant.

Apoptosis and molecular targeting therapy in cancer

Apoptosis is the programmed cell death which maintains the healthy survival/death balance in metazoan cells. Defect in apoptosis can cause cancer or autoimmunity, while enhanced apoptosis may cause degenerative diseases. The apoptotic signals contribute into safeguarding the genomic integrity while defective apoptosis may promote carcinogenesis. The apoptotic signals are complicated and they are regulated at several levels. The signals of carcinogenesis modulate the central control points of the apoptotic pathways, including inhibitor of apoptosis (IAP) proteins and FLICE-inhibitory protein (c-FLIP). The tumor cells may use some of several molecular mechanisms to suppress apoptosis and acquire resistance to apoptotic agents, for example, by the expression of antiapoptotic proteins such as Bcl-2 or by the downregulation or mutation of proapoptotic proteins such as BAX. In this review, we provide the main regulatory molecules that govern the main basic mechanisms, extrinsic and intrinsic, of apoptosis in normal cells. We discuss how carcinogenesis could be developed via defective apoptotic pathways or their convergence. We listed some molecules which could be targeted to stimulate apoptosis in different cancers. Together, we briefly discuss the development of some promising cancer treatment strategies which target apoptotic inhibitors including Bcl-2 family proteins, IAPs, and c-FLIP for apoptosis induction.

Risk factors for ovarian cancers with and without microsatellite instability

OBJECTIVE

The objective of this study was to evaluate the association between microsatellite instability (MSI) status and (1) ovarian cancer risk factors and (2) the distribution of the specific histologic subtypes in a population-based sample of epithelial ovarian cancers.

METHODS

Participants were drawn from 3 population-based studies of primary epithelial ovarian cancer. Tumor DNA was analyzed using 5 standardized microsatellite markers to assess MSI status. Patients were divided into 3 groups (MSI-high, MSI-low, and MSI-stable) according to National Cancer Institute criteria. We compared the prevalence of specific known risk and protective factors among the 3 subgroups, including body mass index, smoking history, parity, BRCA1 and BRCA2 mutation status, past oral contraceptive use, and tubal ligation. Similarly, we compared the distribution of the histologic subtypes among the 3 subgroups.

RESULTS

A total of 917 ovarian cancer patients were included. One hundred twenty-seven (13.8%) cancers were MSI-high. Subgroup analyses according to smoking, body mass index, parity, past oral contraceptive use, and past tubal ligation did not reveal any statistically significant differences among the groups. Among the 29 patients with BRCA1 mutations, 20.7% had MSI-high cancers compared with 5.9% among 17 BRCA2-mutation patients. The proportions of different ovarian cancer histologic findings among the various MSI subgroups were similar.

CONCLUSIONS

The prevalence of risk and protective factors among ovarian cancer patients is similar for cancers with and without MSI. The distributions of MSI do not differ significantly among ovarian cancers with different histologic findings. Ovarian cancer patients with BRCA1 mutations had a 21% rate of MSI-high tumors, compared with 6% among patients with BRCA2 mutations, but this difference was not statistically significant.

Molecular characteristics of malignant ovarian germ cell tumors and comparison with testicular counterparts: implications for pathogenesis

This review focuses on the molecular characteristics and development of rare malignant ovarian germ cell tumors (mOGCTs). We provide an overview of the genomic aberrations assessed by ploidy, cytogenetic banding, and comparative genomic hybridization. We summarize and discuss the transcriptome profiles of mRNA and microRNA (miRNA), and biomarkers (DNA methylation, gene mutation, individual protein expression) for each mOGCT histological subtype. Parallels between the origin of mOGCT and their male counterpart testicular GCT (TGCT) are discussed from the perspective of germ cell development, endocrinological influences, and pathogenesis, as is the GCT origin in patients with disorders of sex development. Integrated molecular profiles of the 3 main histological subtypes, dysgerminoma (DG), yolk sac tumor (YST), and immature teratoma (IT), are presented. DGs show genomic aberrations comparable to TGCT. In contrast, the genome profiles of YST and IT are different both from each other and from DG/TGCT. Differences between DG and YST are underlined by their miRNA/mRNA expression patterns, suggesting preferential involvement of the WNT/β-catenin and TGF-β/bone morphogenetic protein signaling pathways among YSTs. Characteristic protein expression patterns are observed in DG, YST and IT. We propose that mOGCT develop through different developmental pathways, including one that is likely shared with TGCT and involves insufficient sexual differentiation of the germ cell niche. The molecular features of the mOGCTs underline their similarity to pluripotent precursor cells (primordial germ cells, PGCs) and other stem cells. This similarity combined with the process of ovary development, explain why mOGCTs present so early in life, and with greater histological complexity, than most somatic solid tumors.

Colorectal cancer vaccines in clinical trials

This article elucidates current strategies of active immunotherapy for colorectal cancer patients with a focus on T-cell mediated immunotherapy. Poor prognosis of especially stage III and IV colorectal cancer patients emphasizes the need for advanced therapeutic intervention. Here, we refer to clinical trials using either tumor cell-derived vaccines or tumor antigen vaccines with a special interest on safety, induced immune responses, clinical benefit and efforts to improve the clinical impact of these vaccines in the context of colorectal cancer treatment.

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.

Implication of heat shock factors in tumorigenesis: therapeutical potential

Heat Shock Factors (HSF) form a family of transcription factors (four in mammals) which were named according to the discovery of their activation by a heat shock. HSFs trigger the expression of genes encoding Heat Shock Proteins (HSPs) that function as molecular chaperones, contributing to establish a cytoprotective state to various proteotoxic stresses and in pathological conditions. Increasing evidence indicates that this ancient transcriptional protective program acts genome-widely and performs unexpected functions in the absence of experimentally defined stress. Indeed, HSFs are able to re-shape cellular pathways controlling longevity, growth, metabolism and development. The most well studied HSF, HSF1, has been found at elevated levels in tumors with high metastatic potential and is associated with poor prognosis. This is partly explained by the above-mentioned cytoprotective (HSP-dependent) function that may enable cancer cells to adapt to the initial oncogenic stress and to support malignant transformation. Nevertheless, HSF1 operates as major multifaceted enhancers of tumorigenesis through, not only the induction of classical heat shock genes, but also of “non-classical” targets. Indeed, in cancer cells, HSF1 regulates genes involved in core cellular functions including proliferation, survival, migration, protein synthesis, signal transduction, and glucose metabolism, making HSF1 a very attractive target in cancer therapy. In this review, we describe the different physiological roles of HSFs as well as the recent discoveries in term of non-cogenic potential of these HSFs, more specifically associated to the activation of “non-classical” HSF target genes. We also present an update on the compounds with potent HSF1-modulating activity of potential interest as anti-cancer therapeutic agents.

Application of molecular diagnostics for the detection of Lynch syndrome

Lynch syndrome (LS), or hereditary nonpolyposis colorectal cancer, is the most common hereditary colorectal cancer (CRC) syndrome, accounting for approximately 2-5% of all newly diagnosed cases of CRC. Patients with LS have an increased lifetime risk of colorectal (52.2% in women and 68.7% in men) and endometrial cancer (15-70%), as well as certain extra-colonic cancers. Germline mutations in one of several DNA mismatch repair genes underlie LS. Molecular testing has emerged as an indispensable strategy for the diagnosis of LS. The diagnostic work-up of at-risk individuals includes a careful family history evaluation, microsatellite instability, immunohistochemistry and germline DNA analysis. A positive test result can guide clinicians in formulating the appropriate screening, surveillance and management strategies. However, because of the absence of an overt phenotype, such as a diffuse polyposis, it is not always straightforward to recognize LS clinically.

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.

Distinct high-profile methylated genes in colorectal cancer

Background

Mutations and promoters' methylation of a set of candidate cancer genes (CAN genes) are associated with progression of colorectal cancer (CRC). We hypothesized that these genes' promoters are inactivated through epigenetic silencing and may show a different profile in high-risk populations. We investigated the status of CAN gene methylation and CHD5 protein expression in African American CRC tissue microarrays (TMA) using immunohistochemical staining.

Methodology/Principal Findings

The promoter methylation status of the CAN genes was studied by methylation-specific PCR (MSP) in 51 Iranians (a white population) and 51 African Americans (AA). Microsatellite instability (MSI) was analyzed as well. The differential frequency of methylation for each gene was tested by chi-square analysis between the two groups based on matched age and sex. CHD5 protein expression was evaluated in moderate to well differentiated and poorly differentiated carcinomas compared to matched normal tissue using TMA. In addition, the correlation between these epigenetic biomarkers and various clinicopathological factors, including, age, location, and stage of the disease were analyzed.

Seventy-seven and 34% of tumors were distal in Iranian and African American patients, respectively. In both populations, the percentage of methylation was >65% for SYNE1, MMP2, APC2, GPNMB, EVL, PTPRD, and STARD8, whereas methylation was <50% for LGR6, RET, CD109, and RNF. The difference in methylation between the two populations was statistically significant for CHD5, ICAM5 and GPNMB. Thirty-one percent AA tumors showed MSI-H, compared to 28% in Iranians.

Conclusions/Significance

A significantly higher methylation rate was found for GPNMB, ICAM5, and CHD5 genes in AA patients compared to Iranians. These genes might play a role in the high incidence and aggressiveness of CRC in the AA population. The hypermethylation of the CAN genes can be considered as a marker of colon carcinogenesis.

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.

Systematic review and meta-analysis of ovarian cancers: estimation of microsatellite-high frequency and characterization of mismatch repair deficient tumor histology

PURPOSE

A meta-analytic approach was used to estimate the frequency of: (a) microsatellite instability-high (MSI-H) phenotype in unselected ovarian cancers and (b) various histologic subtypes of mismatch repair (MMR)-deficient epithelial ovarian cancers.

METHODS

A systematic search of the Medline electronic database was conducted to identify articles published between January 1, 1966, and December 31, 2007, that examined MMR deficiency in ovarian cancers. Data were extracted on the study population, sample size, MSI-H frequency, and histology of MMR-deficient ovarian tumors.

RESULTS

The pooled proportion of MSI-H ovarian cancers was 0.12 [95% confidence interval (CI), 0.08-0.17] from 18 studies with 977 cases. The proportion of histologic subtypes in the pooled analysis from 15 studies with 159 cases was serous at 0.32 (95% CI, 0.20-0.44), mucinous at 0.19 (95% CI, 0.12-0.27), endometrioid at 0.29 (95% CI, 0.22-0.36), clear cell at 0.18 (95% CI, 0.09-0.28), and mixed at 0.24 (95% CI, 0.07-0.47). There was significant heterogeneity between studies.

CONCLUSIONS

The frequency of the MSI-H phenotype in unselected ovarian cancers approximates 12%. MMR-deficient ovarian cancers also seem to be characterized by an overrepresentation of nonserous histologic subtypes. Knowledge of histologic subtype may aid clinicians in identifying the relatively large proportion of ovarian cancers due to MMR defects; such knowledge has potential implications for medical management.

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.

Microsatellite instability and mismatch repair protein defects in ovarian epithelial neoplasms in patients 50 years of age and younger

Ovarian malignancies occurring in the setting of hereditary nonpolyposis colorectal carcinoma syndrome typically present in young women, often as the first or "sentinel" cancer, but the frequency of microsatellite instability (MSI) and mismatch repair (MMR) defects in ovarian surface epithelial malignancies in women <or=50 years of age is neither well known nor well tested. Fifty-two ovarian surface epithelial carcinomas, including 4 with synchronous endometrial carcinomas, were identified in patients 50 years of age or younger and evaluated for evidence of MSI and MMR protein deficiency. Each case was tested for MSI by multiplex polymerase chain reaction amplification of the National Cancer Institute reference panel (BAT25, BAT26, D2S123, D5S346, and D17S250) and deficiency of MMR protein expression by immunohistochemistry (MLH1, MSH2, MSH6, and PMS2). MMR protein expression and MSI (in a subset of cases) were also evaluated in 50 unselected ovarian serous tumors of low malignant potential , a tumor common in younger women. Defects in MMR were detected in 5 of 52 (10%) ovarian carcinomas by at least 1 testing method, including 2 of 4 (50%) ovarian cancers presenting with synchronous endometrial cancer. Three of the 5 (60%) ovarian carcinomas were clear cell carcinomas (17% of all pure clear cell carcinomas) and the remaining 2 were high-grade carcinomas with endometrioid and mixed histology. Loss of MSH2 and MSH6 was detected in all of the affected clear cell carcinomas and a synchronous endometrial cancer with endometrioid histology. Loss of 1 or more MMR proteins was initially noted in 10/50 ovarian serous tumors of low malignant potential on tissue microarray, but further testing on full tissue sections showed intact protein expression and microsatellite stability in all informative cases. This study demonstrates a 10% rate of MMR-deficient ovarian cancer in women <or=50 years of age. MMR-deficient ovarian cancer is frequently associated with loss of expression of MSH2 and MSH6 proteins and clear cell histology. The occurrence of MMR inactivation in a significant proportion of ovarian clear cell carcinomas (17% in this study) suggests that this tumor may warrant targeted testing in women <or=50 years of age.

Prediction of the immunogenic potential of frameshift-mutated antigens in microsatellite instable cancer

Microsatellite instable (MSI) cancers express frameshift-mutated antigens, the C-terminal polypeptides of which are foreign to the immune system. Consequently, these antigens constitute a unique pool of tumor-specific antigens that can be exploited for patient diagnosis and selective, immune-mediated targeting of cancers. However, other than their sequence, very little is known about the characteristics of the majority of these proteins. We therefore developed a methodology for predicting their immunogenic behavior that is based on a gene-expression system, in which each of the proteins was fused to a short C-terminal polypeptide comprising two epitopes that can be readily detected by T-cells and antibodies, respectively. In this manner, accumulation of the antigens and processing of peptides derived thereof into MHC can be monitored systematically. The antigens, which accumulate in the cells in which they are synthesized, are of primary interest for cancer immunotherapy, because peptide epitopes derived thereof can be presented by dendritic cells in addition to the tumor cells themselves. As a result, these antigens constitute the best targets for a coordinated immune response by both CD8+ and CD4+ T-cells, which increases the likelihood that tumor-induced immunity would be detectable against these antigens in cancer patients, as well as the potential value of these antigens as components of anticancer vaccines. Our data indicate that, of 15 frameshift-mutated antigens examined in our study, 4 (TGFbetaR2-1, MARCKS-1, MARCKS-2 and CDX2-2) are of primary interest, and 4 additional antigens (TAF1B-1, PCNXL2-2, TCF7L2-2 and Baxalpha+1) are of moderate interest for further tumor immunological research.

Clinical significance of microsatellite instability in sporadic epithelial ovarian tumors

PURPOSE

We evaluated the expression of microsatellite instability (MSI) in sporadic ovarian tumors using 5 standard and 9 new MSI markers to determine the clinical significance of MSI in sporadic epithelial ovarian tumors.

MATERIALS AND METHODS

MSI was examined in 21 borderline and 25 malignant ovarian tumors. Polymerase chain reaction (PCR) was performed using the 5 markers recommended by the National Cancer Institute (NCI) for colon cancer and 9 additional markers. MSI was determined using fractional analysis by mixing the PCR products and size markers.

RESULTS

Using the 5 conventional MSI markers, MSI was found in 4 of 46 (8.6%) ovarian tumors, including 2 of 21 (9.5%) borderline ovarian tumors and 2 of 25 (8%) malignant ovarian tumors. Using the 9 additional MSI markers, MSI was observed in 7 of 46 (15.2%) ovarian tumors, including 3 of 21 (14.3%) borderline ovarian tumors and 4 of 25 (16%) malignant ovarian tumors. There was no statistically significant difference between MSI and clinicopathological factors, including histology and stage, although there was a trend toward an increased incidence of MSI in the serous type.

CONCLUSION

MSI was infrequent in ovarian tumors, including both borderline and malignant tumors. MSI was found to be uncommon in sporadic ovarian tumors, even by using additional MSI markers. The clinical significance of MSI is not strong in patients with sporadic ovarian tumors.

Loss of DNA mismatch repair protein hMSH6 in ovarian cancer is histotype-specific

Microsatellite instability (MSI) due to defects in DNA mismatch repair genes may be involved in the development of a subset of human ovarian carcinomas. The role of one such gene, hMSH6, in ovarian cancer is not well documented. We investigated the expression of hMSH6 protein in different histotypes of ovarian carcinoma and the associations between loss of hMSH6 protein and tumor grade, disease stage, familial history of cancer and patient survival. We stained an ovarian carcinoma tissue microarray consisting of formalin-fixed, paraffin-embedded tissue samples from 322 patients with an anti-hMSH6 antibody and scored the results semiquantitatively as negative or positive. Twelve cases were excluded owing to loss of cores during staining. Absence of hMSH6 protein was noted in 20 of 230 serous carcinomas (8.7%), in 7 of 16 clear cell carcinomas (43.7%), in 4 of 34 endometrioid carcinomas (11.7%), in 1 of 14 malignant mixed Müllerian tumors, 2 of 6 mucinous carcinomas, 0 of 2 transitional cell carcinomas and in 0 of 8 undifferentiated carcinomas. Loss of hMSH6 protein was not associated with survival, patient age, tumor grade, or disease stage but was associated with clear cell, mucinous and endometrioid carcinoma histology (P<0.007). These findings indicate that loss of hMSH6 expression in ovarian carcinoma is more common in certain histologic subtypes, particularly in clear cell, endometrioid, and mucinous carcinoma, suggesting that loss of hMSH6 function may participate in the pathogenesis of these subtypes of cancer. Loss of hMSH6 expression did not predict survival and was not associated with disease stage, tumor grade, patient age or family history of cancer.

The high frequency of de novo promoter methylation in synchronous primary endometrial and ovarian carcinomas

PURPOSE

The methylation status of hMLH1, CDKN2A, and MGMT was investigated in a panel of synchronous cancers of the ovary and endometrium, fulfilling the clinicopathologic criteria for independent primary tumors to define the possible role of epigenetic mechanisms in the development of these cancers.

EXPERIMENTAL DESIGN

Bisulfite-converted DNA from 31 tumors (13 endometrial and 18 ovarian carcinomas) and from matched normal tissue of 13 patients was analyzed by a methylation-specific PCR assay at the CpG-rich 5' regions of all three genes. In all tumors, we also investigated the presence of microsatellite instability and hMLH1 immunohistochemical expression in relation to hMLH1 hypermethylation status.

RESULTS

Methylation of hMLH1, CDKN2A, and MGMT was detected in 39%, 41%, and 48% of endometrial and ovarian tumors, respectively. hMLH1 hypermethylation was observed in all tumors of five patients, and it was invariably associated with loss of hMLH1 protein and presence of microsatellite instability. CDKN2A and MGMT methylation was randomly detected among both endometrial (45% and 24% of cases, respectively) and ovarian carcinomas (39% and 39% of cases, respectively). Concordant methylation at two or three genes was observed in 35% of cases.

CONCLUSIONS

Epigenetic inactivation of hMLH1, CDKN2A, and MGMT may be a common and early event in the development of synchronous primary endometrial and ovarian carcinomas and may qualify as a marker of a field cancerization encompassing the ovary and endometrium. Detection of MGMT hypermethylation may be useful to define a set of gynecologic malignancies with a specific sensitivity to alkylating chemotherapy.

Absence of Microsatellite Instability and Lack of Evidence for Subclone Diversification in the Pathogenesis and Progression of Mycosis Fungoides

Mutator phenotypes with microsatellite instability (MSI) correlated with defects in the mismatch repair system are characteristic for a subset of solid neoplasms, but are rare in non-Hodgkin lymphomas. In mismatch repair-deficient mice, however, mutator-type non-Hodgkin lymphomas are the most frequent tumors. To determine the role of MSI in mycosis fungoides, we compared the states of the eight dinucleotide microsatellite loci DXS418, DXS453, DXS556, DXS1060, D1S201, D6S260, D9S162, and D10S215 in tumor cells of 12 well-characterized patients at early- and advanced-stage diseases to matched healthy tissue. We did not find any MSI, although all but one patient had progressed to advanced-stage disease within the timeframe of the study. Concordantly, the expression of mismatch repair genes was normal. These results suggest that progressive accumulation of mutations as detected by MS analysis does not play a major role in the pathogenesis or in the progression of mycosis fungoides.

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.

Patterns of loss of heterozygosity at 10q23.3 and microsatellite instability in endometriosis, atypical endometriosis, and ovarian carcinoma arising in association with endometriosis

Genetic aberrations, such as loss of heterozygosity (LOH) and mutations leading to functional inactivation of the PTEN tumor suppressor gene, located on chromosome 10q23.3, have been shown to be associated with approximately one third of ovarian adenocarcinomas. In addition, microsatellite instability (MSI) leading to the functional inactivation of the PTEN gene has also been reported for ovarian adenocarcinomas with frequencies varying from 6 to 37%. However, the frequency of PTEN gene abnormalities has not been well studied or evaluated in lesions such as typical and atypical endometriosis. The aim of this study was to investigate a possible sequential progression from endometriosis through atypical endometriosis to ovarian carcinoma by assessing LOH at 10q23.3 and MSI in those entities. Genomic DNA was analyzed for LOH and MSI at 3 loci on chromosome 10, using polymerase chain reaction amplification. Significant differences in LOH were seen between endometriosis (4.3%) and ovarian carcinoma (23.5%) at D10S608. The differences at the other 2 loci were not significant. A high frequency of MSI was found in endometriosis (82.6%) and atypical endometriosis (75%); however, the differences were not significant. These results suggest that LOH at D105608 may possibly be an important molecular event in the progression of endometriosis to carcinoma. This study highlights that endometriosis and atypical endometriosis might act as precursor lesions that have the potential to progress into ovarian adenocarcinoma.

The contribution of the hereditary nonpolyposis colorectal cancer syndrome to the development of ovarian cancer

OBJECTIVE

Ovarian cancer has one of the highest fractions of hereditary cases. The hereditary breast and ovarian cancer syndrome, primarily due to mutations in BRCA1 and BRCA2, is the main cause of heredity, but also the hereditary nonpolyposis colorectal cancer (HNPCC) syndrome confers an increased risk of ovarian cancer. In order to clarify the contribution of HNPCC to the development of ovarian cancer, we collected data on family history of cancer and characterized MMR function in a consecutive series of 128 tumors unselected for age at diagnosis and previously characterized for BRCA gene mutations.

METHODS

Expression of the MMR proteins MLH1, PMS2, MSH2, and MSH6 was analyzed by immunohistochemistry using tissue microarray sections. Tumors with reduced staining or loss of staining were also analyzed for microsatellite instability (MSI).

RESULTS

Loss of MMR protein expression was identified in 3 ovarian cancers, all of which had a MSI-high phenotype. DNA sequence analysis revealed disease-causing germline mutations (deletions of exons 4-6 in MLH1 and a 1-nucleotide deletion in exon 5 of MSH6) in two patients diagnosed at ages 40 and 49 years, both of whom had family histories suggestive of HNPCC. The genetic defect in the third case, which was a 47-year old woman without knowledge about her family history with loss of MLH1/PMS2 expression in the tumor tissue, remains elusive. A family history suggestive of HNPCC was identified in an additional case, but this tumor showed normal, retained MMR protein expression and a microsatellite stable phenotype.

CONCLUSIONS

About 2% of ovarian cancer is caused by germline mutations in the MMR-genes, a minor proportion as compared to the contribution of the BRCA-genes (11% in the present series). However, identification of HNPCC patients is important since it allows inclusion of high-risk individuals into control programs aimed at preventing the more frequent colorectal and endometrial cancers. Tumors within the HNPCC-spectrum should therefore be included when recording a family history of cancer among patients diagnosed with ovarian cancer.

Synchronous endometrioid carcinomas of the uterine corpus and ovary: alterations in the beta-catenin (CTNNB1) pathway are associated with independent primary tumors and favorable prognosis

Diagnosis of synchronous endometrioid carcinomas of the uterine corpus and ovary as either separate independent primary or as metastatic tumors requires careful consideration of a number of gross and histological features. Although such assessment is often sufficient, recent evidence has suggested that molecular analysis may facilitate the diagnosis in problematic cases. Furthermore, as independent synchronous tumors limited to the uterus and ovary are generally associated with favorable outcome, determination of genetic alterations associated with this group of neoplasms may indicate molecular markers of less aggressive behavior. We examined 12 cases of synchronous carcinomas of the uterus and ovary, correlating conventional gross and histological parameters with molecular genetic alterations common to single endometrioid carcinomas occurring in these sites. We identified a frequency of molecular alterations in both independent and metastatic tumors, including microsatellite instability (uterine tumors, 50% and 67%, respectively; ovarian tumors, 33% and 67%) and PTEN mutations (uterine tumors, 38% and 100%; ovarian tumors, 33% and 83%) that is higher than that observed in single sporadic tumors. Loss of heterozygosity for chromosome 17p and 10q was also frequently observed. Nuclear immunoreactivities for beta -catenin and CTNNB1 mutations were restricted to independent uterine and ovarian tumors and were absent in all of the metastatic tumors, providing direct evidence for a divergence of molecular oncogenetic mechanisms in the subset of synchronous endometrioid carcinomas. Furthermore, our data show that molecular genetic classification of synchronous independent versus metastatic tumors based on beta -catenin expression/mutation correlates with clinical outcome.

Molecular mechanisms of drug resistance

Resistance to chemotherapy limits the effectiveness of anti-cancer drug treatment. Tumours may be intrinsically drug-resistant or develop resistance to chemotherapy during treatment. Acquired resistance is a particular problem, as tumours not only become resistant to the drugs originally used to treat them, but may also become cross-resistant to other drugs with different mechanisms of action. Resistance to chemotherapy is believed to cause treatment failure in over 90% of patients with metastatic cancer, and resistant micrometastic tumour cells may also reduce the effectiveness of chemotherapy in the adjuvant setting. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanisms of drug resistance that operate to reduce drug sensitivity in cancer cells. Drug resistance can occur at many levels, including increased drug efflux, drug inactivation, alterations in drug target, processing of drug-induced damage, and evasion of apoptosis. Advances in DNA microarray and proteomic technology, and the ongoing development of new targeted therapies have opened up new opportunities to combat drug resistance. We are now able to characterize the signalling pathways involved in regulating tumour cell response to chemotherapy more completely than ever before. This will facilitate the future development of rational combined chemotherapy regimens, in which the newer targeted therapies are used in combination with cytotoxic drugs to enhance chemotherapy activity. The ability to predict response to chemotherapy and to modulate this response with targeted therapies will permit selection of the best treatment for individual patients.

Molecular genetic alterations in endometrioid carcinomas of the ovary: similar frequency of beta-catenin abnormalities but lower rate of microsatellite instability and PTEN alterations than in uterine endometrioid carcinomas

Endometrioid carcinomas of the ovary closely resemble their uterine counterparts. It has been suggested that the former tumors have the same molecular alterations (microsatellite instability [MSI], PTEN, and beta-catenin) described in endometrioid carcinomas of the uterus. We analyzed 55 ovarian carcinomas, including 22 endometrioid, 18 clear cell, and 15 mixed types. MSI was detected in 5 of 39 cases (13%). MLH1 promoter hypermethylation was identified in 2 of the 5 MSI-positive tumors. PTEN was mutated in 5 of 54 cases (9%); of these, 3 had MSI and exhibited frameshift mutations in short-coding mononucleotide repeats. Beta-catenin nuclear expression was detected in 11 of 54 cases (20%) by immunostaining; of these, 7 exhibited CTNNB1 gene mutations. These alterations were found more frequently in endometrioid carcinomas than in tumors of the other 2 groups. Among the former tumors, MSI was detected in 3 of 17 cases (17.5%); PTEN mutations, in 3 of 21 (14%); and beta-catenin, in 8 of 21 (38%). The molecular alterations were found more often in tumors associated with endometriosis than in tumors without endometriosis. Six endometrioid tumors demonstrating matrix metalloproteinase-7 (MMP-7) immunoreactivity with nuclear accumulation of beta-catenin had good outcomes, in contrast to poor outcomes in 7 of 9 predominantly nonendometrioid tumors demonstrating expression of MMP-7 only. We found a similar frequency of beta-catenin abnormalities but lower rates of MSI and PTEN alterations than in uterine endometrioid carcinomas. Alterations in beta-catenin and PTEN genes, as well as MSI, are frequent in low-stage ovarian carcinomas of endometrioid type that have a favorable prognosis.

Evidence that both genetic instability and selection contribute to the accumulation of chromosome alterations in cancer

Cancer cells contain many genetic alterations, and genetic instability may be important in tumourigenesis. We evaluated 58 breast and ovarian cancer cell lines for microsatellite instability (MSI) and chromosomal instability (CIN). MSI was identified in 3/33 breast and 5/25 ovarian cell lines, and 7/8 MSI lines showed an inactivation of mismatch repair. Average ploidy by centromeric fluorescence in situ hybridization (FISH) of MSI (n = 8, average ploidy = 2.65) and microsatellite stable (MSS; n = 7, average ploidy = 3.01) cell lines was not different, due to the presence of three aneuploid MSI lines, and two near-diploid MSS lines. However, the variability of the centromeric FISH data was different between MSI and MSS (P = 0.049). The complexity of structural chromosomal rearrangements was not different between MSI and MSS. Thus, MSI and numerical CIN are not mutually exclusive, and structural CIN occurs independently of MSI or numerical CIN. Dynamic genetic instability was evaluated in three cell lines-MSI diploid (MT-3), MSS diploid (SUM159) and MSS aneuploid (MT-1). Ten clones of each of these cell lines were analysed by centromeric FISH and six-colour chromosome painting. The variation in chromosome number was different among all three cell lines (P < 0.001). MT-3 appeared numerically constant (94% of centromeric FISH signals matched the mode). SUM159 was 88% constant; however, 7% of cells had duplicated chromosomes. MT-1 was 82% constant; most changes were chromosomal losses. The six-colour FISH data showed that SUM159 had more stable structural chromosomal alterations (e.g. chromosomal translocations) compared with MT-3 and MT-1, but had no increase in unstable changes (e.g. chromatid breaks) when compared with MT-3. MT-1 had fewer unstable changes than both MT-3 and SUM159. These data suggest that numerical CIN may contribute to aneuploidy, but that selection plays an important role, particularly for the accumulation of structural chromosomal changes.

Differential expression of protease activated receptor 1 (Par1) and pY397FAK in benign and malignant human ovarian tissue samples

Protease activated receptors (PAR) form a family of G-protein coupled receptors (GPCR) encoding their own ligands and uniquely activated via proteolytic cleavage. Although proteases in general have been implicated in the remodeling of the extracellular tumor microenvironment, the role of cell surface receptors activated by proteolysis is now emerging. In our present study we investigated the expression pattern of protease activated receptor 1 hPar1 in ovarian carcinoma tissue samples. Abundant hPar1 mRNA and protein were detected in "low malignant potential" and in invasive carcinomas, regardless of the histological subtype. In contrast, no hPar1 expression was detected on the cell surface of normal ovarian epithelium. The differential expression pattern of hPar1 was shown by in situ hybridization, immunohistochemistry and semi-quantitative RT-PCR analyses. In early stages of ovarian carcinoma (Ia), the contra lateral normal ovary showed strong PAR1 expression as opposed to the lack of expression in the ovarian epithelium obtained from normal individuals. In parallel, we analyzed the expression pattern of alphavbeta5 integrin and of activated focal adhesion kinase (FAK), a major focal contact protein, in these tissues. Although abundant expression of alphavbeta5 integrin was observed in all tissues specimens examined, regardless of either normal or malignant, the level of activated FAK was differentially expressed. Phosphorylated FAK was seen in invasive ovarian carcinoma, but not in the normal ovarian epithelium. The abundant hPar1 levels in pathological malignant ovarian carcinoma is likely to transmit signals leading to the phosphorylation of FAK and thereby alterations in the integrin functional state. Altogether our data suggest that hPar1 and FAK cooperate to promote ovarian cancer malignancy.

Pathophysiological Dynamics of Human Ovarian Surface Epithelial Cells in Epithelial Ovarian Carcinogenesis

Epithelial ovarian cancer is responsible for almost half of all the deaths from female genital tract tumors. Major impediments to the clinical treatment of this disease are the relatively asymptomatic progression and a lack of knowledge regarding defined precursor or malignant lesions. Most epithelial ovarian cancers are thought to arise from the transformation of ovarian surface epithelial cells, a single continuous layer of flat-to-cuboidal mesothelial cells surrounding the ovary. To improve our understanding of the pathogenesis of epithelial ovarian cancer, it is necessary to study the biological characteristics of normal ovarian surface epithelial cells. However, this approach has been hampered by the inability to purify and culture such human cells. During the past decade, procedures to isolate and culture human ovarian surface epithelial cells have been developed, and, subsequently, using viral oncogenes, several immortalized cells have been established. This new experimental system is being employed to improve our understanding of the genetic changes leading to the initiation of epithelial ovarian cancer and to identify events in the cancer's development. This review mainly describes the biological dynamics of ovarian surface epithelial cells in the pathogenesis of epithelial ovarian cancer, focusing on humans and excluding small animal models.

The replication error phenotype is associated with the development of distant metastases in hormonally treated patients with breast carcinoma

BACKGROUND

The positive replication error (RER+) phenotype defines a distinct subgroup of tumors with specific clinical, pathologic, and molecular features that have been documented well in hereditary nonpolyposis colon carcinoma (HNPCC). More recently, this phenotype also has been described in breast carcinoma.

METHODS

To determine the effect of RER phenotype on prognosis in patients with breast carcinoma, the authors examined matched archival tumor and normal tissue from 100 women with Stage I and Stage II breast carcinoma, all of whom were treated with hormonal therapy. Patients had been followed for a minimum of 5 years or until death. Seven microsatellite loci were examined, including hMLH1 (3p22, D3S1611), hMSH2 (2p16, D2S123), NM23-H1 (17q21), TP53-Dint (17p13), TP53-Penta (17p13), APC (5q21, D5S346), and HPC1 (1q24, D1S2883). The RER+ phenotype was defined as the presence of allelic shifts at three of the seven loci examined.

RESULTS

Twenty-five percent of patients were classified with the RER+ phenotype based on these criteria. The two groups, women with positive RER status and women with negative RER status, were comparable in terms of other factors that may influence prognosis: age, tumor size, lymph node status, disease stage, and estrogen receptor status. The development of distant metastases to the lung, liver, or brain was correlated significantly with the positive RER phenotype, with a relative risk of 2.625 (95% confidence interval, 1.059-6.057).

CONCLUSIONS

The presence of high-frequency RER+ may predict for the development of distant metastatic disease in patients with early-stage breast carcinoma who are treated with hormonal therapy.

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

Microsatellite instability and loss of heterozygosity has been implicated in ovarian carcinogenesis. The reported frequency of microsatellite instability in human ovarian cancer varies significantly owing to the use of heterogeneous tumor histotypes and various microsatellite markers in different laboratories. In this study, we determined the frequency of microsatellite instability in 74 ovarian endometrioid carcinomas using four microsatellite markers (BAT25, BAT26, D5S346, D17S250), and examined hMLH1 and hMSH2 protein expression. In all, 20% of the tumors were microsatellite instability high (two or more markers showing instability) and 12% were microsatellite instability low (one marker showed instability). Loss of hMLH1 and/or hMSH2 expression was found in nine of 15 microsatellite instability-high tumors. The microsatellite instability-high phenotype tended to occur more frequently in low-grade tumors (P=0.053), but did not correlate with clinical stage. Totally, 38% of cases also displayed loss of heterozygosity at D17S250; this loss of heterozygosity was associated with high clinical stage (P=0.097). Our results indicate that both microsatellite and loss of heterozygosity at D17S250 are involved in the development of ovarian endometrioid carcinoma.

Genetic alterations in ovarian cancer cells that might account for sensitivity to chemotherapy in patients

The cellular response to anticancer agent treatments is determined by many factors that could be altered in tumor cells. The induction of apoptosis of cancer cells is thought to be important for the overall response of these cells. Despite the introduction of new and potent anticancer agents, the survival rate for patients with ovarian cancer remains poor. In general ovarian cancer cells present a poor propensity to undergo apoptosis, which could be one of the reasons for this relatively poor response observed in the clinic. Induction of apoptosis is the result of activation and repression of pro- and antiapoptotic genes, which are regulated by complex mechanisms. Many cancer cells activate a "survival" program to escape disruption and allow propagation. In this review we have analyzed the role of genetic alterations observed in ovarian cancer cells in determining cellular response to drug treatment.

Mismatch repair genes and microsatellite instability as molecular markers for gynecological cancer detection

Due to major developments in genetics over the past decade, molecular biology tests are serving promising tools in early diagnosis and follow-up of cancer patients. Recent epidemiological studies revealed that the risk for each individual to develop cancer is closely linked to his/her own genetic potentialities. Some populations that are defective in DNA repair processes, for example in Xeroderma pigmentosum or in the Lynch syndrome, are particularly prone to cancer due to the accumulation of mutations within the genome. Such populations would benefit from the development of tests aimed at identifying people who are particularly at risk. Here, we review some data suggesting that the inactivation of mismatch repair is often found in endometrial cancer and we discuss molecular-based strategies that would help to identify the affected individuals in families with cases of glandular malignancies.

Microsatellite instability, MLH-1 promoter hypermethylation, and frameshift mutations at coding mononucleotide repeat microsatellites in ovarian tumors

BACKGROUND

Microsatellite instability (MI) is frequent in endometrial carcinomas (ECs), but its occurrence in ovarian tumors is uncertain. Microsatellite instability positive ECs frequently are associated with frameshift mutations in coding mononucleotide tracts in IGFIIR, BAX, hMSH6, and hMSH3.

METHODS

DNA from 52 consecutive patients with ovarian tumors (10 benign, 7 borderline, and 35 malignant) was obtained from neoplastic and normal tissue. After preliminary results, the series was expanded by including 41 additional, previously selected, endometrioid and clear cell carcinomas. Microsatellite instability analysis was assessed by evaluating three (CA)n dinucleotide repeats (D2S123, D5S346, D17S250) and two mononucleotide tracts (BAT 25 and BAT 26). Frameshift mutations at coding mononucleotide repeats (IGFIIR, TGF beta II, BAX, hMSH6, and hMSH3) were investigated by single-strand conformation polymorphism analysis and DNA sequencing. MLH-1 methylation was assessed by methylation specific PCR.

RESULTS

Microsatellite instability was identified in only 2 of the 52 (3.8%) tumors of the initial series (1 endometrioid and 1 clear cell carcinoma). After expanding the initial series of 15 endometrioid and clear cell carcinomas with 41 additional endometrioid and clear cell carcinomas, MI was found in 7 of the total series of 56 endometrioid and clear cell carcinomas (12.5%). Frameshift mutations in coding mononucleotide tracts were detected in BAX (6 of 7), IGFIIR (1 of 7), and MSH3 (2 of 7). MLH-1 promoter hypermethylation was identified in three of six MI positive tumors.

CONCLUSIONS

Microsatellite instability was infrequent in this series of ovarian tumors, and it was limited to endometrioid and clear cell carcinomas. Like EC, many ovarian carcinomas with MI follow the same process of MLH-1 promoter methylation and accumulation of mutations in coding mononucleotide tracts.

Microsatellite instability, MLH-1 promoter hypermethylation, and frameshift mutations at coding mononucleotide repeat microsatellites in ovarian tumors

BACKGROUND

Microsatellite instability (MI) is frequent in endometrial carcinomas (ECs), but its occurrence in ovarian tumors is uncertain. Microsatellite instability positive ECs frequently are associated with frameshift mutations in coding mononucleotide tracts in IGFIIR, BAX, hMSH6, and hMSH3.

METHODS

DNA from 52 consecutive patients with ovarian tumors (10 benign, 7 borderline, and 35 malignant) was obtained from neoplastic and normal tissue. After preliminary results, the series was expanded by including 41 additional, previously selected, endometrioid and clear cell carcinomas. Microsatellite instability analysis was assessed by evaluating three (CA)n dinucleotide repeats (D2S123, D5S346, D17S250) and two mononucleotide tracts (BAT 25 and BAT 26). Frameshift mutations at coding mononucleotide repeats (IGFIIR, TGF beta II, BAX, hMSH6, and hMSH3) were investigated by single-strand conformation polymorphism analysis and DNA sequencing. MLH-1 methylation was assessed by methylation specific PCR.

RESULTS

Microsatellite instability was identified in only 2 of the 52 (3.8%) tumors of the initial series (1 endometrioid and 1 clear cell carcinoma). After expanding the initial series of 15 endometrioid and clear cell carcinomas with 41 additional endometrioid and clear cell carcinomas, MI was found in 7 of the total series of 56 endometrioid and clear cell carcinomas (12.5%). Frameshift mutations in coding mononucleotide tracts were detected in BAX (6 of 7), IGFIIR (1 of 7), and MSH3 (2 of 7). MLH-1 promoter hypermethylation was identified in three of six MI positive tumors.

CONCLUSIONS

Microsatellite instability was infrequent in this series of ovarian tumors, and it was limited to endometrioid and clear cell carcinomas. Like EC, many ovarian carcinomas with MI follow the same process of MLH-1 promoter methylation and accumulation of mutations in coding mononucleotide tracts.

Loss of heterozygosity at the RB-1 locus and pRB immunostaining in epithelial ovarian tumors: a molecular, immunohistochemical, and clinicopathologic study

Alterations in the retinoblastoma gene (RB-1) are common in human neoplasia. The frequency of loss of heterozygosity (LOH) at the RB-1 locus on chromosome 13q14 was studied in a series of 51 epithelial ovarian tumors (10 benign, 7 borderline, and 34 malignant). LOH was scored by the absence or reduction of the signal to < 50% of one of the alleles in tumor DNA compared with normal DNA. LOH results were correlated with retinoblastoma protein (pRB) immunostaining. LOH at the RB-1 locus was observed in 9 tumors (17.6%), specifically in 1 of 7 borderline tumors and 8 of 34 ovarian carcinomas (23.5%). Among the malignant tumors, LOH occurred more frequently in carcinomas with serous differentiation (7/23; 30%). A heterogeneous (10% to 70% cells) or diffuse (> 70% cells) pRB immunostaining was less frequent in benign (1/10; 10%) and borderline (2/7; 28%) tumors than in ovarian carcinomas (15/34; 44%), an observation that correlated with the higher proliferative index in carcinomas than in benign and borderline tumors. However, lack or only focal (< 10% cells) pRB immunostaining occurred in the vast majority of tumors with LOH at the RB-1 locus (7/9; 77%), a finding that may suggest a tumor suppressor role for RB-1 in these tumors. The results suggest that RB-1 may play a role in a subset of ovarian carcinomas, particularly those exhibiting serous differentiation.

Molecular genetics of ovarian cancer

This is a review of the approaches that can be used to analyze genetic changes in ovarian cancer. Traditional gene localization methods are discussed, followed by a section on gene identification techniques. Once a putative disease-associated gene has been cloned, mutations have to be identified and analyzed. There are numerous mutation detection methods, and the most common ones are outlined. In the penultimate section, the role of immunohistochemistry as a surrogate method for mutation analysis is considered. Finally, the possible use of functional assays is discussed. At present, it would appear that DNA chip technology for the detection of mutations, and microarray analysis of gene expression, are two important techniques likely to have a significant impact on the genetic analysis of ovarian cancer.

The clinical features of ovarian cancer in hereditary nonpolyposis colorectal cancer

OBJECTIVE

Hereditary nonpolyposis colorectal cancer (HNPCC) is a hereditary cancer susceptibility disorder associated with a very high risk for carcinoma of the colon and an elevated risk for certain extracolonic cancers including ovarian cancer. Our aim in this study was to describe the clinicopathologic features of ovarian cancer in HNPCC family members.

METHODS

. Members of the International Collaborative Group on HNPCC collected retrospective data on 80 ovarian cancer patients who were members of HNPCC families, including 31 known mutation carriers, 35 presumptive carriers (by colorectal/endometrial cancer status), and 14 at-risk family members.

RESULTS

Mean age at diagnosis of ovarian cancer was 42.7. Nonepithelial tumors made up only 6.4% of the cancers, and borderline tumors comprised just 4.1% of the epithelial cancers. Among frankly malignant epithelial cases, most cancers were well or moderately differentiated, and 85% were FIGO stage I or II at diagnosis. Synchronous endometrial cancer was reported in 21.5% of cases.

CONCLUSIONS

Ovarian cancer in HNPCC differs from ovarian cancer in the general population in several clinically important respects. It occurs at a markedly earlier age. It is more likely to be epithelial. If it is a frankly invasive epithelial cancer, it is more likely to be well or moderately differentiated. HNPCC patients with ovarian cancer are more likely to have a synchronous endometrial cancer than other ovarian cancer patients and are more likely to be diagnosed at an early stage.

Microsatellite instability and mutational analysis of transforming growth factor beta receptor type II gene (TGFBR2) in sporadic ovarian cancer

AIMS

To investigate the possible role of mutations in the transforming growth factor beta receptor type II gene (TGFBRII) in ovarian cancer and its relation to microsatellite instability (MSI), 43 sporadic ovarian tumours were analysed for mutations over the entire coding region of the TGFBRII gene.

METHODS

Mutational analysis was performed using the polymerase chain reaction (PCR), single strand conformation polymorphism (SSCP) gel analysis, and direct sequencing. MSI analysis included both mononucleotide and dinucleotide microsatellite markers used for radiolabelling and gene scanning.

RESULTS

No pathogenic mutations were detected, although sequencing of the polyadenine (poly A) tract in exon 3 using conventional techniques revealed a spurious frameshift mutation that was not present in the same samples analysed using a proofreading Taq polymerase. MSI analysis demonstrated an MSI negative phenotype in 40 of the 43 tumours. None of the three MSI positive tumours demonstrated MSI for mononucleotide markers only.

CONCLUSIONS

These findings suggest that: (1) MSI (both conventional and mononucleotide) is infrequent in ovarian cancer and (2) inactivation of the MSH2, MLH1, and MSH6 mismatch repair genes and TGFBR2 gene mutations do not play a major role in ovarian cancer tumorigenesis. The spurious TGFBR2 frameshift mutations detected by sequencing after conventional PCR underline the importance of confirming putative mutations in repetitive sequences by alternative methods.

beta-Catenin expression pattern, beta-catenin gene mutations, and microsatellite instability in endometrioid ovarian carcinomas and synchronous endometrial carcinomas

beta-Catenin gene mutations and microsatellite instability (MI) have been reported in endometrioid ovarian carcinomas. In colon but not endometrial cancer, beta-catenin gene mutations are associated with a replication error phenotype and MI. In this study the authors investigate whether beta-catenin mutations and MI are two independent oncogenic pathways in endometrioid ovarian carcinomas. They also evaluate the usefulness of these molecular markers in determining the primary origin of simultaneous tumors in the ovary and endometrium. This study was performed on 26 patients diagnosed with primary endometrioid ovarian carcinoma, five of whom also had pathologically diagnosed primary synchronous endometrioid endometrial carcinoma. Immunohistochemical and molecular analyses indicated that there were 25 primary ovarian tumors with four primary synchronous endometrial cancers and one ovarian metastasis of a primary endometrial carcinoma. All studies were performed on formalin-fixed, paraffin-embedded tissue samples. The beta-catenin expression pattern (nuclear vs. membranous) was analyzed immunohistochemically. Mutations in exon 3 of the beta-catenin gene were studied by polymerase chain reaction, single-strand conformational polymorphism, and direct sequencing. MI status was established by studying BAT-26 and BAT-25 mononucleotide repeats. In the group with 21 single ovarian tumors, 18 (85%) had beta-catenin nuclear expression, eight (38%) had beta-catenin gene mutations (always associated with beta-catenin nuclear expression), and four (19%) had MI. Only one case (5%) had both beta-catenin gene mutations and MI. The mutations affected one of the serine/threonine residues targeted for phosphorylation by glycogen synthase kinase-3beta or adjacent residues. At codon 32, a GAC-to-TAC (D32Y) change was found; at codon 33, two TCT-to-TGT (S33C) changes were found; at codon 37, three TCT-to-TTT (S37F) changes and one TCT-to-TGT (S37C) change were found; and, lastly, one ACC-to-GCC change at codon 41 (T41A) was detected. Four of the 25 endometrioid ovarian carcinomas (16%) had an associated synchronous endometrial carcinoma. There was a higher percentage of beta-catenin mutations (n = 3, 75%) in synchronous ovarian carcinomas than in single ones, although with a similar percentage of MI (n = 1, 25%). beta-catenin mutations were S37C in two cases and D32G in one. One of the four endometrial carcinomas showed an S33C beta-catenin mutation, and two carcinomas had MI. None of the four tumors had both beta-catenin gene mutation and MI. beta-catenin gene mutations were always associated with a nuclear beta-catenin expression pattern, whereas MI was associated with a membranous pattern. In one patient both the ovarian and the endometrial carcinomas had beta-catenin gene mutations, in another patient both tumors showed MI, whereas in the remaining two patients the ovarian carcinomas showed beta-catenin gene mutations and the endometrial carcinomas showed MI. To summarize, the results of this study suggest that beta-catenin mutations and MI could represent two independent pathways in endometrioid ovarian carcinomas because they occur simultaneously very infrequently (in 5% of these cases). beta-catenin mutations are always associated with a nuclear beta-catenin expression pattern, whereas cases with a replication error -plus phenotype showed no abnormal beta-catenin subcellular localization. The study of the beta-catenin expression pattern, beta-catenin mutations, and MI, together with conventional clinicopathologic findings, could aid in distinguishing between the metastatic or independent origin of simultaneous endometrioid ovarian and endometrial carcinomas. Tumors with identical immunohistochemical and molecular features should therefore be considered to have a common origin.

Precursor lesions of ovarian epithelial malignancy

Most ovarian carcinomas arise from the mesothelial surface lining of the ovaries, or from invaginations of this lining into the superficial ovarian cortex to form cortical inclusion cysts. The native ovarian surface mesothelium is of an 'uncommitted' phenotype, and has potential to modulate to epithelial or mesenchymal phenotypes in response to signals such as those associated with ovulation. The exposure of the mesothelial lining of an inclusion cyst to the ovarian stromal microenvironment may be responsible for the phenotypic change to Müllerian epithelium so commonly seen in these cysts. Müllerian metaplasia is usually to a serous phenotype, and it is possible that undefined molecular events occurring in an inclusion cyst that has undergone Müllerian metaplasia may initiate neoplastic change in these cysts. This may be the developmental pathway of most invasive serous carcinomas. Occasional rare cases of ovarian intraepithelial neoplasia, manifested by epithelial atypia in an inclusion cyst or on the surface epithelium without invasive carcinoma, are identified histologically. Serous borderline tumours represent a separate category and in most cases probably do not progress to frank carcinoma. Mucinous carcinomas may in some cases have arisen from pre-existing benign and borderline mucinous tumours. Endometriosis of the ovary is associated with genetic abnormalities and is frequently found in association with clear cell and endometrioid carcinomas, suggesting that in many cases these latter two types of carcinoma may have arisen directly from endometriotic deposits. Ovaries removed prophylactically from women with a family history of ovarian carcinoma or with a mutation in one of the genes predisposing to ovarian carcinoma should be processed in their entirety, and examined closely not just for obviously neoplastic lesions, but also for more subtle morphological abnormalities of the surface epithelium or the epithelium lining cortical inclusion cysts.

Are DNA mismatch repair deficiencies responsible for accumulation of genetic alterations in epithelial ovarian cancers?

To investigate the association of DNA mismatch repair deficiencies in the development and/or progression of epithelial ovarian cancers, the relationship between replication errors (RERs) and genetic alterations in three genes (p53, c-erbB2, K-ras) and loss of heterozygosity (LOH) on 6q27 was investigated in 70 patients with epithelial ovarian cancers. The presence of RERs was examined by PCR using five microsatellite markers. Mutations of p53 were analyzed by PCR-SSCP and sequencing. Amplification of c-erbB2 was analyzed by Southern blot hybridization. Point mutations of K-ras codon 12 were identified by PCR-PHFA, while 6q27LOH was examined by Southern blot hybridization. As a result, 18 of 70 patients with epithelial ovarian cancers (26%) were RER-positive and 52 patients (74%) were RER-negative. Tumors with two or three genetic alterations accounted for 28% and 33% of RER-positive tumors, respectively, and these were significantly more frequent than in the RER-negative tumors (17% and 6%, respectively)(P =.002). These results are consistent with mismatch repair deficiencies being involved in the development and/or progression of a proportion of epithelial ovarian cancers through accumulation of genetic alterations.

Microsatellite instability is a late event in the carcinogenesis of uterine cervical cancer

OBJECTIVE

The purpose of this study was to elucidate the role of genetic instability and LOH in the progression of cervical cancer and also to analyze for correlations between these genetic abnormalities and the clinicopathological characteristics of cervical cancers.

METHODS

Seventy-two DNA samples were obtained from 29 carcinoma in situ, 8 microinvasive carcinoma, and 35 invasive cancers. Seven highly polymorphic microsatellite markers representing the chromosome 3p, 6p, and 6q arms were examined by PCR amplification.

RESULTS

Microsatellite instability was detected in 8 of 35 (22.9%) invasive cancers and in 1 of 37 (2.7%) early stage cancers (microinvasive cancer and carcinoma in situ). The incidence of MI was statistically higher in invasive cancers (P < 0.02). On the other hand, loss of heterozygosity (LOH) of chromosome 3p was identified in 6/41 (14.6%) invasive cancers and in 3/27 (11.1%) carcinomas in situ. There was no statistical difference between the two groups. There were no significant correlations between the presence of MI or 3p LOH and clinicopathological characteristics including the histological type, FIGO stage, depth of myometrial invasion, lymphovascular involvement, lymph node metastasis, and recurrence.

CONCLUSION

Our results indicate that genomic instability is a late event during the carcinogenesis of cervical cancer and is associated with the conversion of cervical intraepithelial neoplasia to an invasive phenotype. To the contrary, LOH of chromosome 3p plays an early role in the development of cervical intraepithelial neoplasia. No significant correlation was observed between the presence of MI or LOH and clinicopathological characteristics.

Microsatellite instability in germ cell tumors of the testis and ovary

OBJECTIVES

Widespread replication-type error (RER) is a genetic alteration that has been observed in many different neoplasms and has been associated with defective DNA repair activity. There are conflicting data regarding the role that this type of genetic instability plays in the development and progression of adult germ cell tumors.

METHODS

Universal amplification was performed on 104 paired specimens of tumor and constitutional DNA isolated from adult male and female germ cell tumors, in addition to subpopulations of carcinoma in situ (CIS), the precursor of testicular germ cell tumors (TGCTs). Preamplified DNA samples of TGCTs and ovarian germ cell tumors (OGCTs) were assayed for the presence of RER at 78 and 64 microsatellite loci, respectively.

RESULTS

RER was observed at a single microsatellite locus in 7 of 24 individual testicular germ cell tumors, including subpopulations of CIS isolated from one of these patients. There was some evidence of RER clustering for microsatellite loci mapping to the short arm of chromosome 12. Genetic instability was more frequent in OGCTs, with widespread RER observed at 38 of 64 microsatellite loci. These alterations were noted in 12 of 36 malignant OGCTs showing RER at 1 or more loci, including 3 OGCTs demonstrating RER at more than 6 separate microsatellite loci.

CONCLUSIONS

The pathogenetic significance of genetic instability in germ cell tumors remains uncertain, although the results of this study suggest a lesser role in TGCTs compared to that in OGCTs.

DNA replication error is frequent in ovarian granulosa cell tumors

DNA replication errors (RER) have been detected in epithelial ovarian cancers, as well as in other human tumor types. These observations suggest that this genetic defect is present in ovarian granulosa cell tumors, and that a DNA mismatch repair deficiency may be involved in their development and/or progression. We therefore assayed tissue samples from 29 patients with granulosa cell tumors for RER, using polymerase chain reaction (PCR) and 5 microsatellite markers. The RER were observed at greater than or equal to 1 loci in 15 (58%) of 26 informative cases. The incidence of RER was unrelated to the patient's age or the histologic subtype or clinical stage of the tumors. The RER, however, were observed in 57% (8/14) of the informative patients with stage IA disease. These findings suggest that a DNA mismatch repair deficiency may contribute to the pathogenesis of ovarian granulosa cell tumors, and that this deficiency may be an early event in their development and/or progression.

Expression of a homeobox gene (SIX5) in borderline ovarian tumours

AIMS

To assess the expression of SIX5 (a homeobox gene) mRNA in surface coelomic epithelium, endocervical epithelium, Fallopian tube epithelium, and benign, borderline, and malignant epithelial ovarian tumours.

METHODS

10 normal premenopausal ovaries, 10 normal Fallopian tubes, 10 normal cervices, 10 normal postmenopausal ovaries, 10 benign epithelial ovarian tumours, 10 malignant epithelial ovarian tumours, and 40 borderline epithelial ovarian tumours were studied retrospectively. The tissues had been fixed in formalin and embedded in paraffin wax. The tumours had previously been typed into mucinous, serous, or mixed tumours and assigned to the borderline category according to the FIGO/WHO criteria. Expression was assessed by in situ binding of SIX5 specific sense and antisense riboprobes. Hybridization of the riboprobes was detected using a standard immunohistochemical technique and the results correlated with expression in the normal epithelium of the endocervix, Fallopian tube, surface coelomic epithelium, and ovarian tumours.

RESULTS

Expression of SIX5 mRNA was demonstrated in normal Fallopian tube epithelium and normal endocervical epithelium. SIX5 mRNA was not detected in normal ovarian epithelial tissue at any of the times studied during the menstrual cycle. Expression of SIX5 was not shown in benign epithelial ovarian tumours or in any of the malignant epithelial ovarian tumours. In 31 of 37 borderline epithelial ovarian tumours (84%), SIX5 expression was found in the epithelial cells.

CONCLUSIONS

SIX5 expression is present in the normal epithelium throughout most of the female reproductive tract, suggesting it may have a role in maintaining epithelial differentiation in these tissues. SIX5 expression appears to be restricted to borderline epithelial ovarian tumours and may be a marker of epithelial differentiation in these tumours; thus borderline ovarian tumours may not be part of a continuum of disease between benign and malignant epithelial ovarian tumours. Further investigation of expression of SIX5 may clarify the molecular processes that promote differentiation of the ovarian surface epithelium.