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

Interplay between altered metabolism and DNA damage and repair in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy and is often associated with both DNA repair deficiency and extensive metabolic reprogramming. While still emerging, the interplay between these pathways can affect ovarian cancer phenotypes, including therapeutic resistance to the DNA damaging agents that are standard-of-care for this tumor type. In this review, we will discuss what is currently known about cellular metabolic rewiring in ovarian cancer that may impact DNA damage and repair in addition to highlighting how specific DNA repair proteins also promote metabolic changes. We will also discuss relevant data from other cancers that could be used to inform ovarian cancer therapeutic strategies. Changes in the choice of DNA repair mechanism adopted by ovarian cancer are a major factor in promoting therapeutic resistance. Therefore, the impact of metabolic reprogramming on DNA repair mechanisms in ovarian cancer has major clinical implications for targeted combination therapies for the treatment of this devastating disease.

The significance of tissue-agnostic biomarkers in solid tumors: the more the merrier?

INTRODUCTION

To date, several emerging biomarkers have gained considerable interest in the field of predictive molecular oncology. The advent of precision medicine has led to the development of innovative drugs targeting rare molecular pathways independently from histology, defined as tissue-agnostic drugs.

AREAS COVERED

Although there is a lot of promise for this new tissue-agnostic model in the oncological scenario, crucial issues from both the diagnostic and therapeutic standpoint are emerging. This review aims to critically examine the role of tissue-agnostic biomarkers in different solid tumors, focusing on the prevalence and methods of detection of agnostic biomarkers together with drug approvals to guide clinicians in this evolving landscape.

EXPERT OPINION

To strengthen the framework for tissue-agnostic approvals, the dialogue between regulatory, industrial, and academic parties should be intensified. Critical questions include the development of an efficient network system that can overcome the heterogeneity of patients' inclusion criteria along with the increasingly difficult interpretation of next-generation sequencing (NGS) profiling technologies. Cost-effectiveness and risk-benefit studies are needed in the national context considering the modalities of access to diagnostic tests and reimbursement of treatments.

Frequency and clinical features of deficient mismatch repair in ovarian clear cell and endometrioid carcinoma

Objective

To clarify the frequency of deficient mismatch repair (dMMR) in Japanese ovarian cancer patients, we examined microsatellite instability (MSI) status and immunohistochemistry (IHC) subtypes, including endometrioid carcinoma (EMC), clear cell carcinoma (CCC), or a mixture of both (Mix).

Methods

We registered 390 patients who were diagnosed with EMC/CCC/Mix between 2006 and 2015 and treated at seven participating facilities. For 339 patients confirmed eligible by the Central Pathological Review Board, MSI, IHC, and MutL homolog 1 methylation analyses were conducted. The tissues of patients with Lynch syndrome (LS)-related cancer histories, such as colorectal and endometrial cancer, were also investigated.

Results

MSI-high (MSI-H) status was observed in 2/217 CCC (0.9%), 10/115 EMC (8.7%), and 1/4 Mix (25%). Additionally, loss of MMR protein expression (LoE-MMR) was observed in 5/219 (2.3%), 16/115 (14.0%), and 1/4 (25%) patients with CCC, EMC, and Mix, respectively. Both MSI-H and LoE-MMR were found significantly more often in EMC (p<0.001). The median (range) ages of patients with MMR expression and LoE-MMR were 54 (30–90) and 46 (22–76) (p=0.002), respectively. In the multivariate analysis, advanced stage and histological type were identified as prognostic factors.

Conclusion

The dMMR rate for EMC/CCC was similar to that reported in Western countries. In Japan, it is assumed that the dMMR frequency is higher because of the increased proportion of CCC.

The deficient mismatch repair (dMMR) rate in Japanese patients is currently unknown. This study determined the frequency of dMMR in Japanese ovarian cancer patients. The dMMR rate was similar to that reported in Western countries. We identified potential criteria for implementing microsatellite instability and immunohistochemistry analyses in Lynch syndrome screening.

Microsatellite Instability: From the Implementation of the Detection to a Prognostic and Predictive Role in Cancers

Microsatellite instability (MSI) has been identified in several tumors arising from either germline or somatic aberration. The presence of MSI in cancer predicts the sensitivity to immune checkpoint inhibitors (ICIs), particularly PD1/PD-L1 inhibitors. To date, the predictive role of MSI is currently used in the selection of colorectal cancer patients for immunotherapy; moreover, the expansion of clinical trials into other cancer types may elucidate the predictive value of MSI for non-colorectal tumors. In clinical practice, several assays are used for MSI testing, including immunohistochemistry (IHC), polymerase chain reaction (PCR) and next-generation sequencing (NGS). In this review, we provide an overview of MSI in various cancer types, highlighting its potential predictive/prognostic role and the clinical trials performed. Finally, we focus on the comparison data between the different assays used to detect MSI in clinical practice.

Targeting DNA Damage Response Pathway in Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC) is one of the major types of ovarian cancer and is of higher relative prevalence in Asians. It also shows higher possibility of resistance to cisplatin-based chemotherapy leading to poor prognosis. This may be attributed to the relative lack of mutations and aberrations in homologous recombination-associated genes, which are crucial in DNA damage response (DDR), such as BRCA1, BRCA2, p53, RAD51, and genes in the Fanconi anemia pathway. On the other hand, OCCC is characterized by a number of genetic defects rendering it vulnerable to DDR-targeting therapy, which is emerging as a potent treatment strategy for various cancer types. Mutations of ARID1A, PIK3CA, PTEN, and catenin beta 1 (CTNNB1), as well as overexpression of transcription factor hepatocyte nuclear factor-1β (HNF-1β), and microsatellite instability are common in OCCC. Of particular note is the loss-of-function mutations in ARID1A, which is found in approximately 50% of OCCC. ARID1A is crucial for processing of DNA double-strand break (DSB) and for sustaining DNA damage signaling, rendering ARID1A-deficient cells prone to impaired DNA damage checkpoint regulation and hence sensitive to poly ADP ribose polymerase (PARP) inhibitors. However, while preclinical studies have demonstrated the possibility to exploit DDR deficiency in OCCC for therapeutic purpose, progress in clinical application is lagging. In this review, we will recapitulate the preclinical studies supporting the potential of DDR targeting in OCCC treatment, with emphasis on the role of ARID1A in DDR. Companion diagnostic tests (CDx) for predicting susceptibility to PARP inhibitors are rapidly being developed for solid tumors including ovarian cancers and may readily be applicable on OCCC. The potential of various available DDR-targeting drugs for treating OCCC by drawing analogies with other solid tumors sharing similar genetic characteristics with OCCC will also be discussed.

A preoperative prediction model for predicting coexisting adnexa malignancy of patients with G1/G2 endometrioid endometrial cancer

OBJECTIVE

To identify the predictors of coexisting adnexa malignancy (CAM) before surgery for patients with G1/G2 endometrioid endometrial cancer (EEC).

METHODS

Patients with G1/G2 EEC who received surgery in Fudan University Shanghai Cancer Center from 1996 to 2017 were enrolled. Univariate and multivariate logistic regression were performed to identify the predictors for CAM, and the nomogram was constructed and evaluated the discrimination and calibration.

RESULTS

Among the 1511 patients in the study cohort, 66 (4.4%) coexisted adnexa malignancy (51 metastatic and 15 synchronous primaries). In the univariate logistic regression analysis, CA125 level (>35 U/ml), histologic grades, myometrial invasion depth in magnetic resonance imaging (MRI), adnexal involvement in MRI/surgical exploration (SEP) were found to be significant predictors for CAM (P < .001, 0.047, 0.011, <0.001, respectively). The multivariate analysis demonstrated that high CA125 level (P < .001; OR: 2.945; 95%CI: 1.700-5.101), deep myometrial invasion (P = .011; OR: 2.194; 95%CI: 1.200-4.011), and suspected adnexal involvement in MRI/SEP (P < .001; OR: 11.524; 95%CI: 6.726-19.744) were independent predictors for CAM (AUC = 0.786). In 338 patients with MMR results, eighty-seven (25.7%) were detected MSI-high. There were 5.7% (5/87) patients diagnosed with CAM in the MSI-high group compared with 4.4% (11/251) in the MSS group.

CONCLUSIONS

A nomogram with pre- and intra-operative factors was constructed to predict CAM in G1/G2 EEC patients, which may help clinicians in decision-making for ovarian preservation for these patients.

High homogeneity of MMR deficiency in ovarian cancer

OBJECTIVE

Mismatch repair (MMR) deficiency and Bethesda panel microsatellite instability (MSI) are increasingly analyzed to identify tumors that might benefit from immune checkpoint inhibitors, but tumor heterogeneity is a potential obstacle for such analyses. In ovarian cancer, data on intratumoral heterogeneity of MMR deficiency/MSI are lacking.

METHODS

N = 582 ovarian cancers were screened for MMR deficiency by immunohistochemistry (IHC) on a tissue microarray. 10 cases suspect for MMR deficiency were identified among 478 interpretable cancers and repeated IHC on large sections combined with polymerase chain reaction (PCR)-based MSI analysis validated MMR deficiency/MSI in 9 of these tumors.

RESULTS

MMR deficiency/MSI was predominantly seen in endmetrioid cancers (8 of 35, 23%) and also in 1 of 358 serous carcinomas (0.3%), but was absent in 34 mucinous carcinomas, 23 clear cell carcinomas, 17 malignant mixed Mullerian tumors (carcinosarcomas), and 11 mixed carcinomas. MMR deficiency involed protein loss of PMS2/MLH1 in 6 cases and of MSH2 and/or MSH6 in 3 cases. 7 MMR deficient cancers were MSI-high (all endometrioid), one was MSI-low (endometrioid) and one cancer with unequivocal MMR protein loss exhibited microsatellite stability (serous). MLH1 promotor methylation was observed in 4 of 5 endometrioid cancers with MLH1 protein loss. Immunostaining of all available cancer-containing tissue blocks (n = 114) of tumors with confirmed MMR deficiency/MSI revealed uniform MMR status throughout the entire tumor mass.

CONCLUSIONS

Our data show that MSI is present in a substantial proportion of endometrioid ovarian cancers but can also occur in other tumor subtypes. MMR deficiency/MSI typically involves the entire tumor mass, suggesting that MMR inactivation occurs early in tumorigenesis in a subset of ovarian cancers.

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.

Prevalence and molecular characteristics of defective mismatch repair epithelial ovarian cancer in a Japanese hospital-based population

Background

The prevalence and molecular characteristics of defective mismatch repair epithelial ovarian cancers in the Japanese population have scarcely been investigated.

Methods

Immunohistochemistry for mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) was performed in formalin-fixed paraffin-embedded sections prepared from resected primary epithelial ovarian cancers in patients who underwent oophorectomy at our institution between April 2005 and September 2014. Genetic and/or epigenetic alterations of the mismatch repair genes were investigated in patients with loss of any mismatch repair proteins in the tumor.

Results

There were 305 patients with a median age of 54 years (range, 18-83 years). Loss of expression in the ovarian tumor of one or more mismatch repair proteins was observed in 3 of the 305 patients (0.98%): 2 patients MLH1/PMS2 loss and 1 patient showed MSH2/MSH6 loss. Genetic testing of these three patients failed to reveal any pathogenic germline mutations of MLH1 or MSH2. One patient with MLH1/PMS2 loss showed hypermethylation of the promoter region of MLH1. Somatic mutations were found in each of the alleles of MLH1 (c.545dupG and deletion of exons 2-19) in the other patient with MLH1/PMS2 loss. In the patient with MSH2/MSH6 loss, two somatic mutations were detected in MSH2 (c.229_230delAG and c.1861C>T), although we could not determine whether these mutations were biallelic or not.

Conclusions

The prevalence of defective mismatch repair epithelial ovarian cancer in the Japanese hospital-based population was extremely low. Molecular mechanism involved in such defective mismatch repair ovarian cancers seems to be epigenetic events through MLH1 promotor hypermethylation or somatically mutated mismatch repair genes without germline mismatch repair mutation.

Mismatch repair deficiency is associated with MSI phenotype, increased tumor-infiltrating lymphocytes and PD-L1 expression in immune cells in ovarian cancer

OBJECTIVE

The role of mismatch repair (MMR) deficiency in ovarian cancer (OC) pathogenesis and its association with other clinicopathologic features, such as microsatellite instability (MSI) and expression of checkpoint proteins, remain largely elusive.

METHODS

We performed Immunohistochemistry (IHC) for MLH1, MSH2, MSH6 and PMS2 on full-section slides from 419 OCs to assess the MMR status. The clinical relevance of MMR deficiency was analyzed in combination with clinical data. The MSI status (by MSI assay) and expression of CD3, CD8, PD-1 and PD-L1 (by IHC) were compared in OCs with different MMR status.

RESULTS

We found that 2.6% OCs were MMR-negative, 4.3% OCs were MMR-low, and 63.6% of MMR-negative OCs were of endometrioid subtype. A significantly higher proportion of MMR-negative OCs were diagnosed at stage I or II compared to MMR-proficient OCs (p=0.0041). MSI was observed in all tested MMR-negative OCs, 14.3% of tested MMR-low OCs and 3.2% of tested MMR-proficient OCs. In addition, MMR-negative OCs had better progression free survival compared to MMR-proficient and MMR-low OCs (p=0.0046). Furthermore, the majority of OCs were PD-1-positive in intratumoral lymphocytes regardless of MMR status; while MMR-negative OCs exhibited significantly increased CD3+ and CD8+ tumor-infiltrating lymphocytes, and PD-L1+ intratumoral immune cells compared to MMR-proficient OCs.

CONCLUSION

Our data suggests that MMR deficient OC is a unique molecular subgroup, characterized by early stage of diagnosis, MSI phenotype, and increased tumor-infiltrating lymphocytes. These patients may be good candidates for anti-PD-1/PD-L1 therapy.

Screening for Lynch syndrome using risk assessment criteria in patients with ovarian cancer

Objective

Lynch syndrome is a cancer predisposition syndrome caused by germline mutation of DNA mismatch repair (MMR) genes. Lynch syndrome only causes about 0.4% of cases of ovarian cancer, which suggests that universal screening may not be cost-efficient. However, the frequency of Lynch syndrome in ovarian cancer is unclear in the Asian population. The goal of the study was to investigate a screening strategy using family history.

Methods

The subjects were 129 patients with ovarian cancer. Clinical and family history were collected using a self-administered questionnaire, and Society of Gynecologic Oncology (SGO) criteria 2007 and PREMM₅ were used for risk assessment. Microsatellite instability, immunohistochemistry, and methylation of MMR genes were analyzed.

Results

Of the 129 cases, 25 (19.4%) met the SGO criteria, and 4 of these 25 had MSI-high and MMR deficiency. Two cases had loss of MSH2 and MSH6, indicating MSH2 mutation, and the other two had loss of MLH1 and PMS2, including one without MLH1 methylation indicating MLH1 mutation. These results show that screening using family history can detect Lynch syndrome in 12.0% (3/25) of ovarian cancer cases. The 3 cases were positive for PREMM₅, but negative for Amsterdam II criteria and revised Bethesda guidelines. Genetic testing in one case with MSH2 and MSH6 deficiency confirmed the diagnosis of Lynch syndrome with MSH2 mutation.

Conclusion

This is the first study of screening for Lynch syndrome in ovarian cancer using clinical and family history in an Asian population. This approach may be effective for diagnosis in these patients.

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.

Laboratory Assays in Evaluation of Lynch Syndrome in Patients with Endometrial Carcinoma

This article reviews the main tissue testing modalities for Lynch Syndrome in the pathology laboratory, such as immunohistochemistry and PCR based analyses, and discusses their routine application, interpretation pitfalls, and troubleshooting of common technical performance issues. Discrepancies between laboratory and genetic testing may arise, and are examined in the context of the complexity of molecular abnormalities associated with Lynch Syndrome. The merits of targeted versus universal screening in a changing healthcare climate are addressed. In the absence of comprehensive screening programs, specific tumor topography and histological features that may prompt pathologist-initiated molecular tumor testing are outlined.

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.

Features of ovarian cancer in Lynch syndrome (Review)

Lynch syndrome is a hereditary ovarian cancer with a prevalence of 0.9-2.7%. Lynch syndrome accounts for 10-15% of hereditary ovarian cancers, while hereditary breast and ovarian cancer syndrome accounts for 65-75% of these cancers. The lifetime risk for ovarian cancer in families with Lynch syndrome is ~8%, which is lower than colorectal and endometrial cancers, and ovarian cancer is not listed in the Amsterdam Criteria II. More than half of sporadic ovarian cancers are diagnosed in stage III or IV, but ≥80% of ovarian cancers in Lynch syndrome are diagnosed in stage I or II. Ovarian cancers in Lynch syndrome mostly have non-serous histology and different properties from those of sporadic ovarian cancers. A screening method for ovarian cancers in Lynch syndrome has yet to be established and clinical studies of prophylactic administration of oral contraceptives are not available. However, molecular profiles at the genetic level indicate that ovarian cancer in Lynch syndrome has a more favorable prognosis than sporadic ovarian cancer. Inhibitors of the phosphatidylinositol 3-kinase/mammalian target of the rapamycin pathway and anti-epidermal growth factor antibodies may have efficacy for the disease. To the best of our knowledge, this is the first review focusing on ovarian cancer in Lynch syndrome.

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.

Role of the clinical pathology laboratory in the evaluation of endometrial carcinomas for Lynch syndrome

Molecular diagnostic testing of endometrial carcinomas in the pathology laboratory has recently emerged as a key component of the clinical evaluation of Lynch syndrome in many centers. Testing modalities involve immunohistochemical and PCR-based analyses. This article outlines the routine application of these analyses, provides a practical guide for troubleshooting some of the common technical issues related to their performance, and reviews common pitfalls in their interpretation. Discrepancies between tissue testing and genetic testing results are discussed in the context of the current understanding of endometrial cancer biology. The merits of universal versus targeted tissue testing based on clinical patient history and histological tumor appearance are also addressed.

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.

The Role of Ect2 Nuclear RhoGEF Activity in Ovarian Cancer Cell Transformation

Ect2, a Rho guanine nucleotide exchange factor (RhoGEF), is atypical among RhoGEFs in its predominantly nuclear localization in interphase cells. One current model suggests that Ect2 mislocalization drives cellular transformation by promoting aberrant activation of cytoplasmic Rho family GTPase substrates. However, in ovarian cancers, where Ect2 is both amplified and overexpressed at the mRNA level, we observed that the protein is highly expressed and predominantly nuclear and that nuclear but not cytoplasmic Ect2 increases with advanced disease. Knockdown of Ect2 in ovarian cancer cell lines impaired their anchorage-independent growth without affecting their growth on plastic. Restoration of Ect2 expression rescued the anchorage-independent growth defect, but not if either the DH catalytic domain or the nuclear localization sequences of Ect2 were mutated. These results suggested a novel mechanism whereby Ect2 could drive transformation in ovarian cancer cells by acting as a RhoGEF specifically within the nucleus. Interestingly, Ect2 had an intrinsically distinct GTPase specificity profile in the nucleus versus the cytoplasm. Nuclear Ect2 bound preferentially to Rac1, while cytoplasmic Ect2 bound to RhoA but not Rac. Consistent with nuclear activation of endogenous Rac, Ect2 overexpression was sufficient to recruit Rac effectors to the nucleus, a process that required a functional Ect2 catalytic domain. Furthermore, expression of active nuclearly targeted Rac1 rescued the defect in transformed growth caused by Ect2 knockdown. Our work suggests a novel mechanism of Ect2-driven transformation, identifies subcellular localization as a regulator of GEF specificity, and implicates activation of nuclear Rac1 in cellular transformation.

Application of Immunohistochemistry and Molecular Diagnostics to Clinically Relevant Problems in Endometrial Cancer Bojana Djordjevic, Shannon Westin, Russell R. Broaddus

A number of different clinical scenarios are presented in which lab-based analyses beyond the usual diagnosis based on light microscopic examination of H&E stained slides - immunohistochemistry and PCR-based assays such as sequencing, mutation testing, microsatellite instability analysis, and determination of MLH1 methylation - are most helpful for guiding diagnosis and treatment of endometrial cancer. The central goal of this information is to provide a practical guide of key current and emerging issues in diagnostic endometrial cancer pathology that require the use of ancillary laboratory techniques, such as immunohistochemistry and molecular testing. The authors present the common diagnostic problems in endometrial carcinoma pathology, types of endometrial carcinoma, description of tissue testing and markers, pathological features, and targeted therapy.

Crystal structure of Δ-[Ru(bpy)₂dppz]²⁺ bound to mismatched DNA reveals side-by-side metalloinsertion and intercalation

DNA mismatches represent a novel target in the development of diagnostics and therapeutics for cancer, because deficiencies in DNA mismatch repair are implicated in cancers, and cells that are repair-deficient show a high frequency of mismatches. Metal complexes with bulky intercalating ligands serve as probes for DNA mismatches. Here, we report the high-resolution (0.92 Å) crystal structure of the ruthenium 'light switch' complex Δ-[Ru(bpy)(2)dppz](2+) (bpy = 2,2'-bipyridine and dppz = dipyridophenazine), which is known to show luminescence on binding to duplex DNA, bound to both mismatched and well-matched sites in the oligonucleotide 5'-(dCGGAAATTACCG)(2)-3' (underline denotes AA mismatches). Two crystallographically independent views reveal that the complex binds mismatches through metalloinsertion, ejecting both mispaired adenosines. Additional ruthenium complexes are intercalated at well-matched sites, creating an array of complexes in the minor groove stabilized by stacking interactions between bpy ligands and extruded adenosines. This structure attests to the generality of metalloinsertion and metallointercalation as DNA binding modes.

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.

Identification of cancer patients with Lynch syndrome: clinically significant discordances and problems in tissue-based mismatch repair testing

Tissue-based microsatellite instability (MSI) analysis and immunohistochemistry for DNA mismatch repair proteins are accepted screening tools to evaluate patients with cancer for Lynch syndrome. These laboratory analyses are thus important tools in cancer prevention. Quality assurance review was conducted to identify test discordances and problems. These results were then analyzed in conjunction with genetic testing outcomes. Six hundred and forty-six consecutive tumors from 2002 to 2010 were examined. MSI-low tumors were excluded so that 591 tumors comprised the final analyses. Discordance was defined as a discrepancy between immunohistochemical and MSI analysis. Problem was defined as indeterminate or questionable immunohistochemical or MSI results. All results and clinical and family histories were centrally reviewed by two pathologists and one genetics counselor. Discordances and problems were identified in 23 of 591 (3.9%) of the tumors. Twelve of 102 MSI-high carcinomas (11.8%) and one of 489 microsatellite stable tumors had discordant immunohistochemistry. Of these 13 tumors, 11 were from patients who had personal and/or family cancer histories concerning for a germline mismatch repair gene mutation. In addition to discordances, 10 tumors with problematic immunohistochemical profiles were identified. Accurate evaluation of MSI was possible in all tumors. In summary, concordance between immunohistochemistry and MSI was high, particularly for tumors that are microsatellite stable. Greater frequency of test discordance was identified in the tumors that were MSI-high. Thus, a major consequence of the use of immunohistochemistry by itself as a screen is the failure to identify colorectal and endometrial cancer patients who likely have Lynch syndrome.

RhoGDI2 antagonizes ovarian carcinoma growth, invasion and metastasis

Previous studies described functional roles for Rho GDP dissociation inhibitor 2 (RhoGDI2) in bladder, gastric and breast cancers. However, only limited expression and no functional analyses have been done for RhoGDI2 in ovarian cancer. We determined RhoGDI2 protein expression and function in ovarian cancer. First, protein gel blot analysis was performed to determine the expression levels of RhoGDI2 in ovarian cells lines. RhoGDI2 but not RhoGDI1 protein expression levels varied widely in ovarian carcinoma cell lines, with elevated levels seen in Ras-transformed ovarian epithelial cells. Next, immunohistochemistry was performed to detect RhoGDI2 expression in patient samples of ovarian cysts and ovarian cancer with known histological subtype, stage, grade and outcome. RhoGDI2 protein was significantly overexpressed in high-grade compared with low-grade ovarian cancers, correlated with histological subtype, and did not correlate with stage of ovarian cancer nor between carcinomas and benign cysts. Unexpectedly, stable suppression of RhoGDI2 protein expression in HeyA8 ovarian cancer cells increased anchorage-independent growth and Matrigel invasion in vitro and in tail-vein lung colony metastatic growth in vivo. Finally, we found that RhoGDI2 stably-associated preferentially with Rac1 and suppression of RhoGDI2 expression resulted in decreased Rac1 activity and Rac-associated JNK and p38 mitogenactivated protein kinase signaling. RhoGDI2 antagonizes the invasive and metastatic phenotype of HeyA8 ovarian cancer cells. In summary, our results suggest significant cell context differences in RhoGDI2 function in cancer cell growth.

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.

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.

Sampling strategies for tissue microarrays to evaluate biomarkers in ovarian cancer

INTRODUCTION

Tissue microarrays (TMA) enable rapid analysis of biomarkers in large-scale studies involving archival tumor specimens, however, their utility in heterogeneous tumors such as ovarian cancer is limited.

METHODS

In this study, immunohistochemical analysis was done on TMAs comprised of epithelial ovarian cancer (EOC) to estimate the prevalence of loss of expression of three mismatch repair proteins. TMAs were initially created using cores sampled from the center of donor tissue blocks from 59 EOC cases. Full sections were subsequently created and levels of expression were compared between tissues sampled from the central portion versus the periphery. Follow-up analyses were done by obtaining cores from the periphery of up to five additional donor blocks per case. A linear mixed model for each protein was used to investigate differences between results from the initial and follow-up blocks.

RESULTS

In the original TMAs created using centrally sampled cores, loss of mismatch repair expression was noted in 17 (29%) of the 59 cases. By comparison, analyses from peripherally sampled cores revealed loss of expression in only 6 of these 17 cases. For each protein, significant differences (P < 0.05) were detected between results from the initial donor block and the majority of the follow-up blocks.

CONCLUSIONS

Our investigations, based on EOC, suggest that sampling variability in protein expression may result when TMAs are used. Thus, at least for EOC, it is important to preferentially sample from the periphery of tumor blocks where exposure to tissue fixatives is optimal.

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.

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.

Expression of mismatch repair proteins, hMLH1/hMSH2, in non-small cell lung cancer tissues and its clinical significance

BACKGROUND

hMLH1 and hMSH2 have been implicated to be involved in the DNA mismatch repair (MMR) system. The purpose of this study is to investigate the expression of hMLH1 and hMSH2 DNA MMR proteins in non-small cell lung cancer (NSCLC) tissue and to elucidate their clinical significance.

METHODS

The hMLH1 and hMSH2 protein expression was evaluated by immunohistochemistry for a consecutive series of 113 NSCLC patients. The expressions of each protein were examined for an association with the clinicopathological variables, including genetic alterations analyzed by high resolution fluorescent microsatellite analysis.

RESULTS

Regarding the hMLH1 expression, the MSI-positive patients showed significantly lower scores than the MSI-negative patients. For hMSH2 expression, the patients with a 20 or higher pack-year index (PYI) showed significantly higher scores than the patients with a PYI less than 20. The expression status of proteins did not affect both the disease free and overall survival of the patients. No significant correlation was observed among the scores for the proteins.

CONCLUSIONS

The expressions of hMLH1 and hMSH2 are independently regulated and play different roles in NSCLC. The genetic instability is possibly due to the reduced expression of hMLH1 protein, and hMSH2 expression is associated with smoking status.

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.