Mismatch Repair Proteins Research Articles

Impact of mismatch repair deficiency on tumour regression grade after neoadjuvant chemotherapy in localized gastroesophageal adenocarcinoma.

The use of neoadjuvant chemotherapy (NAC) in patients with mismatch repair (MMR) deficient (dMMR) localized gastric and oeso-gastric junction (OGJ) adenocarcinoma is subject of debate. Histological response assessment might help to better evaluate the impact of dMMR on response to NAC. Patients with localized gastric/OGJ adenocarcinoma resected after NAC were retrospectively identified. MMR protein expression status was assessed by immunohistochemistry. The primary objective was the frequency of histological responders to NAC defined by tumour regression grade (TRG) using Mandard's (TRG1-2) and Becker's (TRG1) classifications, according to the MMR status. In total, 247 patients with 43 dMMR and 204 pMMR gastric/OGJ adenocarcinoma were identified. Among dMMR tumours, 18 (42%) arose from the OGJ. Histological response (Becker TRG1-2) was observed for 28% and 35% of dMMR and pMMR tumours, respectively (p=0.35). Similar results were observed with Mandard classification. With a median follow-up of 37.5 months, median disease-free and overall survival were not reached for the dMMR group. Histological response after NAC in patients with localized dMMR gastric/OGJ adenocarcinoma is not statistically different to those with pMMR tumours. This study provides additional data for the discussion about avoiding NAC in patients with dMMR gastric/OGJ adenocarcinomas.

Prognostic value of mismatch repair deficiency in patients receiving first-line fluoropyrimidine plus platinum chemotherapy for metastatic, recurrent, or locally advanced unresectable gastric cancer.

461 Background: In localized gastric cancer (GC), deficient mismatch repair (dMMR) tumors reportedly have a favorable prognosis. However, a potentially detrimental effect of the dMMR status was suggested in patients treated with adjuvant chemotherapy. It remains unclear whether the mismatch repair (MMR) status can impact clinical outcomes in patients with metastatic GC (mGC) receiving palliative chemotherapy. We examined the impact of the MMR status on survival outcomes of patients with HER2-negative mGC receiving first-line fluoropyrimidine plus platinum (FP) chemotherapy. Methods: We reviewed patients with histologically confirmed metastatic, recurrent, or locally advanced unresectable adenocarcinoma of the stomach or gastroesophageal junction receiving first-line FP chemotherapy between January 2015 and August 2018 at Asan Medical Center, Korea. MMR status was correlated with clinical characteristics and survival outcomes for patients with available MMR immunohistochemistry results. Results: Of 895 patients, we analyzed 543 with available MMR protein expression results, and dMMR was detected in 4.4% (n=24). Patients with dMMR exhibited a significantly higher median age than those with proficient MMR (pMMR) (64 vs. 58 years, p=0.044). No signet ring cell carcinoma (SRCC) was detected among dMMR tumors, whereas SRCC was found in 17.5% of pMMR tumors. Based on our prognostic model (Koo DH et al, 2011), only 4.2% of patients with dMMR were classified as the poor-risk group (vs. 16.8% of patients with pMMR, p=0.097). No significant difference in progression-free survival (PFS) was noted between patients with dMMR and pMMR tumors (median, 5.6 vs. 5.8 months, p=0.266). Patients with dMMR tumors tended to have better overall survival than those with pMMR tumors; this difference was not statistically significant (median, 17.9 vs. 12.2 months, p=0.183). In the good-risk subgroup, patients with dMMR tumors had a significantly worse PFS than those with pMMR tumors (median, 5.6 vs. 9.2 months, p=0.009); multivariate analysis revealed that MMR status was an independent factor for poor PFS in this subgroup. Conclusions: Survival outcomes of dMMR mGC did not differ from pMMR in patients who received first-line FP chemotherapy. However, in the good-risk subgroup, patients with dMMR tumors had a significantly shorter PFS than those with pMMR, suggesting a potentially reduced efficacy of cytotoxic chemotherapy in these patients.

Discordance between germline genetic findings and abnormal tumor immunohistochemistry staining of mismatch repair proteins in individuals with suspected Lynch syndrome.

Tumor immunohistochemical staining (IHC) of DNA mismatch repair (MMR) proteins is often used to guide germline genetic testing and variant classification for patients with suspected Lynch syndrome. This analysis examined the spectrum of germline findings in a cohort of individuals showing abnormal tumor IHC. We assessed individuals with reported abnormal IHC findings and referred for testing with a six-gene syndrome-specific panel (n=703). Pathogenic variants (PVs) and variants of uncertain significance (VUS) in MMR genes were designated expected/unexpected relative to IHC results. The PV positive rate was 23.2% (163/703; 95% confidence interval [CI], 20.1%-26.5%); 8.0% (13/163; 95% CI, 4.3%-13.3%) of PV carriers had a PV in an unexpected MMR gene. Overall, 121 individuals carried VUS in MMR genes expected to be mutated based on IHC results. Based on independent evidence, in 47.1% (57/121; 95% CI, 38.0%-56.4%) of these individuals the VUSs were later reclassified as benign and in 14.0% (17/121; 95% CI, 8.4%-21.5%) of these individuals the VUSs were reclassified as pathogenic. Among patients with abnormal IHC findings, IHC-guided single-gene genetic testing may miss 8% of individuals with Lynch syndrome. In addition, in patients with VUS identified in MMR genes predicted to be mutated by IHC, extreme caution must be taken when the IHC results are considered in variant classification.

Current Landscape and Potential Challenges of Immune Checkpoint Inhibitors in Microsatellite Stable Metastatic Colorectal Carcinoma.

Colorectal cancer (CRC) is the third most frequent cancer and the second most common cause of cancer-related death in Europe. High microsatellite instability (MSI-H) due to a deficient DNA mismatch repair (dMMR) system can be found in 5% of metastatic CRC (mCRC) and has been established as a biomarker of response to immunotherapy in these tumors. Therefore, immune checkpoint inhibitors (ICIs) in mCRC with these characteristics were evaluated with results showing remarkable response rates and durations of response. The majority of mCRC cases have high levels of DNA mismatch repair proteins (pMMR) with consequent microsatellite stability or low instability (MSS or MSI-low), associated with an inherent resistance to ICIs. This review aims to provide a comprehensive analysis of the possible approaches to overcome the mechanisms of resistance and evaluates potential biomarkers to establish the role of ICIs in pMMR/MSS/MSI-L (MSS) mCRC.

Unexpected moves: a conformational change in MutSα enables high-affinity DNA mismatch binding.

The DNA mismatch repair protein MutSα recognizes wrongly incorporated DNA bases and initiates their correction during DNA replication. Dysfunctions in mismatch repair lead to a predisposition to cancer. Here, we study the homozygous mutation V63E in MSH2that was found in the germline of a patient with suspected constitutional mismatch repair deficiency syndrome who developed colorectal cancer before the age of 30. Characterization of the mutant in mouse models, as well as slippage and repair assays, shows a mildly pathogenic phenotype. Using cryogenic electron microscopy and surface plasmon resonance, we explored the mechanistic effect of this mutation on MutSα function. We discovered that V63E disrupts a previously unappreciated interface between the mismatch binding domains (MBDs) of MSH2 and MSH6 and leads to reduced DNA binding. Our research identifies this interface as a 'safety lock' that ensures high-affinity DNA binding to increase replication fidelity. Our mechanistic model explains the hypomorphic phenotype of the V63E patient mutation and other variants in the MBD interface.

Synchronous colorectal malignancies with distinct morphology and mismatch repair protein immunoprofiles forming a fistula tract: a case report

Synchronous colorectal carcinomas occur in approximately 3.5% of all colorectal carcinoma cases. Studies have shown that many synchronous carcinomas have different profiles of microsatellite instability status in the same patient. We present a case to highlight the contrasting histological features and immunoprofiles of synchronous medullary carcinoma and adenocarcinoma in the ascending colon, forming a fistula tract. The adenocarcinoma showed retained mismatch repair protein staining with immunohistochemistry, while the medullary carcinoma showed loss of MLH1 and PMS2, with BRAF V600E mutation confirmed on molecular testing.

Age is the best predictor of MLH1 promotor methylation in mismatch repair deficient endometrial carcinoma

Background: When endometrial carcinoma immunohistochemistry displays mismatch repair (MMR) protein loss, it is accompanied by reflex MLH1-promoter methylation testing. Hypermethylation associated with de novo functional loss is distinct from germline pathogenic variants seen in Lynch syndrome.

Noninvasive detection of microsatellite instability in patients with endometrial cancer.

The analysis of mismatch repair proteins in solid tissue is the standard of care (SoC) for the microsatellite instability (MSI) characterization in endometrial cancer (EC). Uterine aspirates (UAs) or circulating-DNA (cfDNA) samples capture the intratumor heterogeneity and provide a more comprehensive and dynamic molecular diagnosis. Thus, MSI analysis by droplet-digital PCR (ddPCR) in UAs and cfDNA can provide a reliable tool to characterize and follow-up the disease. The UAs, paraffin-embedded tumor tissue (FFPE) and longitudinal plasma samples from a cohort of 90 EC patients were analyzed using ddPCR panel and compared to the SoC. A high concordance (96.67%) was obtained between the analysis of MSI markers in UAs and the SoC. Three discordant cases were validated as unstable by ddPCR on FFPE samples. Besides, a good overall concordance (70.27%) was obtained when comparing the performance of the ddPCR assay on UAs and cfDNA in high-risk tumors. Importantly, our results also evidenced the value of MSI analysis to monitor the disease evolution. MSI evaluation in minimally invasive samples shows great accuracy and sensitivity and provides a valuable tool for the molecular characterization and follow-up of endometrial tumors, opening new opportunities for personalized management of EC.

B7-H4 Further Stratifies Patients With Endometrial Cancer Exhibiting a Nonspecific Molecular Profile.

Endometrial cancer is classified into 4 molecular subtypes: DNA polymerase epsilon ultramutated, mismatch repair deficient, p53 mutant, and nonspecific molecular profile (NSMP). Additional biomarkers are urgently needed to better characterize the NSMP subtype, the largest group with heterogeneous pathologic features and prognoses. To investigate the expression of B7 homolog 3 (B7-H3), B7 homolog 4 (B7-H4), and V-set and immunoglobulin domain containing 3 (VSIG-3, a ligand for B7-H5) in 833 patients with endometrial cancer and determine their associations with clinicopathologic and molecular features as well as survival outcomes. Molecular classification was determined by polymerase epsilon sequencing and immunohistochemical staining for p53 and mismatch repair proteins. B7-H3, B7-H4, VSIG-3, and programmed death ligand-1 (PD-L1) were detected via immunohistochemistry. The positivity rates for B7-H3 in each of the tumor and immune cells, B7-H4 (exclusively in tumor cells), and VSIG-3 (exclusively in tumor cells) were 89.0%, 42.3%, 71.5%, and 99.8%, respectively. B7-H3 and B7-H4 positivity in tumor cells was associated with favorable pathologic features and prognosis. In contrast, B7-H3 expression in immune cells was frequent in samples with unfavorable pathologic features; those with p53-mutant subtype, PD-L1 positivity, and a high density of CD8+ T cells; and in patients with poor prognoses. Positive B7-H4 expression was a predictor of improved survival in patients with the NSMP subtype independent of tumor stage or pathologic features. The NSMP subgroup of endometrial cancer can be further stratified by B7-H4 status. Incorporating B7-H4 status into the molecular classification of NSMP could improve the ability to predict disease relapse.

Diagnostic and therapeutic challenges of glioblastoma as an initial malignancy of constitutional mismatch repair deficiency (CMMRD): two case reports and a literature review

BackgroundConstitutional mismatch repair deficiency (CMMRD) results from a biallelic germline pathogenic variant in a mismatch repair (MMR) gene. The most common CMMRD-associated malignancies are brain tumors; an accurate diagnosis is challenging when a malignant brain tumor is the only tumor at presentation. We describe two cases of glioblastoma as the initial CMMRD malignancy and discuss current diagnostic and therapeutic challenges.Case presentationTwo children with brain tumors without remarkable family history had biallelic pathogenic germline variants in PMS2. Patient 1: A 6-year-old girl presented biallelic PMS2 germline pathogenic variants. Glioblastomas at the left frontal lobe and right temporal lobe were resistant to immune-checkpoint inhibitor, temozolomide, and bevacizumab. Patient 2: A 10-year-old boy presented biallelic PMS2 germline variants. His glioblastoma with primitive neuroectodermal tumor-like features responded to chemoradiotherapy, but he developed advanced colon cancer and acute lymphocytic leukemia. In both patients, only a monoallelic PMS2 germline variant was detected by conventional gene tests. PMS2 immunohistochemistry showed lack of staining at both the tumors and normal tissue as vascular endothelial cells. Further gene tests revealed large genomic deletion including the entire PMS2 gene, confirming biallelic PMS2 germline variants.ConclusionConventional multi-gene panel tests are insufficient for detecting large deletions of MMR genes, resulting in misdiagnoses of CMMRD as Lynch syndrome. PMS2 variants have low cancer penetrance; family histories may thus be absent. Long-range gene analyses or immunohistochemical staining of MMR proteins in normal tissue should be considered for pediatric brain tumors with a single allele MMR variant when CMMRD is suspected.

Unique Patterns of Heterogeneous Mismatch Repair Protein Expression in Colorectal Cancer Unveil Different Degrees of Tumor Mutational Burden and Distinct Tumor Microenvironment Features

Mismatch repair (MMR) protein expression in colorectal cancer (CRC) cells is usually homogeneously retained or lost. Rare lesions may show a heterogeneous pattern of MMR protein expression. We evaluated MMR protein expression (MLH1, MSH2, MSH6, and PMS2) in 200 CRCs, identifying 3 groups with proficient MMR protein expression (MMRp), deficient MMR protein expression (MMRd), and heterogeneous MMR protein expression (MMRh). MMRh tumors were microdissected on the basis of the expression of the heterogeneous marker. DNA was extracted and subjected to targeted sequencing. RNA was purified from bulk tumors of all MMRh cases and in a control series of 15 MMRp and 10 MMRd CRCs and analyzed using the PanCancer IO 360 Panel (NanoString Technologies). Twenty-nine of the 200 cases (14.5%) were MMRd. Nine cases (4.5%) showed a heterogeneous pattern of MMR expression, with 6 tumors harboring concomitant loss of one of the other MMR proteins, thus featuring areas with double loss at immunohistochemistry (IHC) testing (MMRh double-loss cases). Four of the 6 MMRh double-loss cases were suitable for a separate sequence variant analysis of IHC double-negative and IHC single-negative components of the tumor. In all lesions, both components exhibited a high tumor mutation burden (TMB). Nevertheless, a significant increase in TMB in the double-negative components was observed (mean TMB: negative, 70 mut/Mb vs positive, 59 mut/Mb) because of a higher number of subclonal variants compared with the other component. Comparative gene expression analyses among MMRd, MMRp, and MMRh CRCs highlighted differential gene expression patterns and an increased number of tumor-infiltrating lymphocytes in MMRh lesions, which is also characterized by a substantial population of exhausted CD8+ lymphocytes. We describe a unique subgroup of CRCs showing heterogeneous expression of MMR proteins in a background of concomitant loss of one of the other markers.

Nontraditional Roles of DNA Polymerase Eta Support Genome Duplication and Stability.

DNA polymerase eta (Pol η) is a Y-family polymerase and the product of the POLH gene. Autosomal recessive inheritance of POLH mutations is the cause of the xeroderma pigmentosum variant, a cancer predisposition syndrome. This review summarizes mounting evidence for expanded Pol η cellular functions in addition to DNA lesion bypass that are critical for maintaining genome stability. In vitro, Pol η displays efficient DNA synthesis through difficult-to-replicate sequences, catalyzes D-loop extensions, and utilizes RNA-DNA hybrid templates. Human Pol η is constitutively present at the replication fork. In response to replication stress, Pol η is upregulated at the transcriptional and protein levels, and post-translational modifications regulate its localization to chromatin. Numerous studies show that Pol η is required for efficient common fragile site replication and stability. Additionally, Pol η can be recruited to stalled replication forks through protein-protein interactions, suggesting a broader role in replication fork recovery. During somatic hypermutations, Pol η is recruited by mismatch repair proteins and is essential for VH gene A:T basepair mutagenesis. Within the global context of repeat-dense genomes, the recruitment of Pol η to perform specialized functions during replication could promote genome stability by interrupting pure repeat arrays with base substitutions. Alternatively, not engaging Pol η in genome duplication is costly, as the absence of Pol η leads to incomplete replication and increased chromosomal instability.

Incorporating Molecular Classification When Stratifying the Survival Risk of Patients with High-Grade Endometrial Carcinomas.

Assessing survival risk in patients with high-grade endometrial carcinomas has remained challenging. We aimed to investigate the distribution of molecular subtypes and assess their prognostic role in a large cohort of 355 patients with high-grade endometrial carcinoma. Molecular classification was determined using DNA polymerase epsilon (POLE) sequencing as well as immunohistochemical staining for p53 and mismatch repair (MMR) proteins. Endometrial carcinomas were stratified into four subtypes: POLE ultramutated, MMR-deficient, non-specific molecular profile (NSMP), and p53-mutant. This study included 177 and 178 patients with endometrioid and non-endometrioid carcinomas, respectively. Forty-two patients (11.8%) were categorized as POLE ultramutated, 106 (29.9%) as MMR-deficient, 128 (36.1%) as p53-mutant, and 79 (22.2%) as NSMP. Patients of different molecular subtypes had distinct survival times; molecular classification, but not histotype, was significantly associated with survival outcomes. When incorporating molecular classification into the stratification model, 52 patients (15.5%) switched risk groups, with 40 (11.9%) shifting to a lower risk for having a POLE mutation and 12 (3.6%) shifting to a higher risk owing to p53-mutant status. Molecular classification may provide more accurate prognostic information among patients with high-grade endometrial carcinomas and improve their stratification for purposes of clinical management.

Extensive molecular profiling of squamous cell anal carcinoma in a phase 2 trial population: Translational analyses of the “CARACAS” study

BackgroundMolecular characteristics of squamous cell anal carcinoma (SCAC) are poorly explored. Immune checkpoint inhibitors showed limited activity in phase I/II trials, but predictive and prognostic biomarkers are lacking. Patients and methodsIn the phase II randomised trial CARACAS (NCT03944252), avelumab alone (Arm A) or with cetuximab (Arm B) was tested in pre-treated advanced SCAC , with overall response rate being the primary end-point. On pre-treatment tumour tissue samples, we assessed Human papillomavirus status, programmed-death ligand 1 (PD-L1) expression, mismatch repair proteins expression, tumour mutational burden (TMB) and comprehensive genomic profiling by FoundationOne CDx. Tumour-infiltrating lymphocytes were characterised on haematoxylin-eosine-stained samples. Primary objective was to describe response to immunotherapy in the CARACAS trial population according to molecular and histological characteristics. Secondary objectives were to assess progression-free survival (PFS) and overall survival (OS) according to molecular biomarkers. ResultsHigh PD-L1 (>40 with combined positive score) was significantly more frequent in patients with disease control (p = 0.0109). High TMB (>10 mutations per megabase) was related to better OS (hazard ratio (HR) = 0.09; 95%confidence interval (CI) 0.01–0.68; p = 0.019) and PFS (HR = 0.44; 95%CI = 0.15–1.27; p = 0.129). High expression of PD-L1 conferred longer OS (HR = 0.46; 95%CI = 0.19–1.08; p = 0.075) and PFS (HR = 0.42; 95%CI = 0.20–0.92; p = 0.03). Neither OS (HR = 1.30; 95%CI = 0.72–2.36; p = 0.39) or PFS (HR = 1.31; 95%CI = 0.74–2.31; p = 0.357) was affected by high (>1.2) Tumour-infiltrating lymphocytes count. High TMB and PD-L1identified patients were with significantly better OS (HR = 0.33; 95%CI = 0.13–0.81; p = 0.015) and PFS (HR = 0.48; 95%CI = 0.23–1.00; p = 0.015). ConclusionsTo our knowledge, TranslaCARACAS is the first study to document prognostic role of TMB and PD-L1 in advanced SCAC patients treated with immune checkpoint inhibitors.

Fast and label-free automated detection of microsatellite status in early colon cancer using artificial intelligence integrated infrared imaging

PurposeMicrosatellite instability (MSI) due to mismatch repair (MMR) defects accounts for 15–20% of colon cancers (CC). MSI testing is currently standard of care in CC with immunohistochemistry of the four MMR proteins representing the gold standard. Instead, label-free quantum cascade laser (QCL) based infrared (IR) imaging combined with artificial intelligence (AI) may classify MSI/microsatellite stability (MSS) in unstained tissue sections user-independently and tissue preserving. MethodsParaffin-embedded unstained tissue sections of early CC from patients participating in the multicentre AIO ColoPredict Plus (CPP) 2.0 registry were analysed after dividing into three groups (training, test, and validation). IR images of tissue sections using QCL-IR microscopes were classified by AI (convolutional neural networks [CNN]) using a two-step approach. The first CNN (modified U-Net) detected areas of cancer while the second CNN (VGG-Net) classified MSI/MSS. End-points were area under receiver operating characteristic (AUROC) and area under precision recall curve (AUPRC). ResultsThe cancer detection in the first step was based on 629 patients (train n = 273, test n = 138, and validation n = 218). Resulting classification AUROC was 1.0 for the validation dataset. The second step classifying MSI/MSS was performed on 547 patients (train n = 331, test n = 69, and validation n = 147) reaching AUROC and AUPRC of 0.9 and 0.74, respectively, for the validation cohort. ConclusionOur novel label-free digital pathology approach accurately and rapidly classifies MSI vs. MSS. The tissue sections analysed were not processed leaving the sample unmodified for subsequent analyses. Our approach demonstrates an AI-based decision support tool potentially driving improved patient stratification and precision oncology in the future.

Histopathologic Features for Overall Survival in Merkel Cell Carcinoma: A Case Series with Intact Mismatch Repair Protein Expression.

In a study of Merkel cell carcinoma (MCC), a fusion transcript between MLH1 and SPATA4 was identified. This fusion has the potential to generate the inactive or dominant-negative form of the protein. Therefore, we aimed to investigate whether mismatch repair protein deficiency occurr in MCC cases or not, in addition to the overall survival association with histopathologic features. A retrospective review of 15 patients diagnosed with a biopsy-proven Merkel Cell Carcinoma between 2012 and 2019 was performed. Mismatch repair (MMR) protein expressions were evaluated by immunohistochemistry. The median follow-up time was 36 months (mean 41, range 2-103 months). Six (40%) patients died during follow-up. The overall survival (OS) at 1 year, 2 years, 3 years, and 5 years were 87%, 80%, 62%, and 53%, respectively. The patients diagnosed at < 60 years had an improved OS compared to those ≥60 years of age (p=0.016). Patients in clinical stage I had better OS than patients in clinical stage IV (p=0.011). Cases with pathological tumor stage (pT) 1 had better OS than pT3 and pT4 (p=0.045). Adjuvant radiotherapy or adjuvant radiotherapy+chemotherapy treatment improved OS compared to adjuvant chemotherapy (p=0.003). MMR protein nuclear expression was intact in 12 cases available for immunohistochemical study. To the best of our knowledge, this is the second study that preferentially investigated the mismatch repair protein status of Merkel Cell Carcinoma. No mismatch repair protein deficiency of MCC cases was identified in the current study.

Mis-Match Repair (MMR) Protein Expression and Microsatellite Instability (MSI) Analysis in Sporadic Adenocarcinoma Diagnosed on Colonoscopic Biopsy

Background and aim Colorectal adenocarcinoma is a major cause of morbidity and mortality worldwide. Mismatch repair MMR protein expression plays a crucial role in the development and progression of colorectal adenocarcinomas. Immunohistochemistry IHC is a widely used technique to assess MMR protein expression. However there is limited data on the prospective evaluation of MMR protein expression by IHC on endoscopic biopsies of colorectal adenocarcinomas. In this study we aimed to evaluate the MMR protein expression by IHC on endoscopic biopsies of colorectal adenocarcinomas at a tertiary care center.Methods Forty-Two colonoscopic endoscopic biopsies pathologically diagnosed as colorectal adenocarcinoma were analyzed for IHC expression of MMR proteins MLH1 PMS2 MSH2 and MSH6.Results Out of the 42 cases 22 52.3 were mismatch repair proficient pMMR while the remaining 20 47.6 were mismatch repair deficient dMMR. MLH1PMS2- was the most common pattern accounting for 20 of dMMR cases and MLH1-PMS2-MSH2-MSH6- or the ldquoNull Patternrdquo was the least common with 10 of dMMR cases.Conclusion Evaluation of MMR proteins using immunohistochemistry is relatively easy in routine testing and is a useful tool in detecting MSI in CRC.nbspnbsp

Expression of PD-L1 in Microsatellite Instability High Tumours: A Retrospective Study

Introduction: Microsatellite Instability (MSI) is the hallmark of Lynch syndrome/Constitutional Mismatch Repair Deficiency (CMMRD) and is also found in many sporadic cancers like colorectal cancer, endometrial, gastric, small intestine, urothelial, central nervous system and sebaceous gland neoplasms. MSI is a predictive biomarker for immunotherapy and Immunohistochemistry (IHC) antibodies against four Mismatch Repair (MMR) proteins: MutL Homolog 1 (MLH1), MutS Homolog 2 (MSH2), MutS Homolog 6 (MSH6) and Postmeiotic Segregation increased 2 (PMS2) can identify the MSI status of the tumour. In addition to MSI, immune checkpoint programmed cell death protein 1 (PD-1) expression and its ligand PD-L1 are biomarkers that can predict response to immunotherapy. Considering this increasing interest to identify deficient MMR (dMMR) status in different cancers, authors have assessed the expression of PDL1 and status of MSI in various cancer types. Aim: To evaluate the expression of PD-L1 in MSI-high status tumours. Materials and Methods: This retrospective cross-sectional study was done in the Department of Pathology, Panimalar Medical College Hospital and Research Institute for a period of six months from July 2022 to December 2022. A total of 151 cases were identified for the period of three years from January 2020 to December 2022. The slides and blocks were retrieved from the archives. Tumour sections from the paraffin embedded tissues were deparaffinised and antigen retrieval was done. IHC using four antibodies (MLH1, MH2, MSH6 and PMS2) was performed on these slides to assess the MSI status. The slides were reviewed and were further subjected to PD-L1 IHC. PD-L1 expression on tumour cells was compared with the MSI status of different cancer types. The p-value was calculated using t-test and p&lt;0.5 was considered statistically significant. Statistical analysis was done using International Business Machines (IBM) Statistical Package for the Social Sciences (SPSS) software version 21.0. Results: A total of 151 cases were included in the present study. A positive nuclear stain for the four MMR proteins denote expression of wild type MMR proteins, hence MSI low status. A loss of nuclear expression denotes mutation of MMR proteins and hence MSI high (MSI-H) status. The MSI was high in nine out of 48 cases (18.75%) of colon cancer, three out of 15 cases (20%) of endometrial cancers, three out of 20 cases (15%) of gastric cancers. Rest were one out of sixteen cases of ovarian cancer, one out of two malignant melanoma and one out of three glioblastoma. Out of these, PD-L1 was positive in seven of the 18 MSI-H cases (38.88% of MSI-H cases). The MSI was low/ stable in the remaining 133 cases. The p-value of significance was 0.03 (statistically significant). Conclusion: This study shows a significant association of MSI-H with PD-L1 expression in tumours. Further large scale studies can help in assessing the role of PD-L1 as an effective therapeutic biomarker in MSI-high status patients who can benefit from targeted therapy

Screening of Endometrial Cancer Related to Lynch Syndrome in China by Suction Curettage-Based Cytology and Histology: A Retrospective Study.

To explore the feasibility of sampling Chinese patients by suction curettage for cytological and histological screening of endometrial cancer related to Lynch syndrome. This retrospective study enrolled patients who underwent endometrial biopsy at our hospital between May 2018 and January 2019. Endometrial sampling (cytological and micro-histological specimens) was conducted by suction curettage. The gold standard for diagnosis was traditional sharp dilation and curettage (D&C). The sensitivity, specificity, and diagnostic accuracy of cytology, micro-histology, and the combination of cytology and micro-histology were calculated. Additionally, receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic efficiency of three screening methods. Mismatch repair proteins were further detected using immunohistochemistry (IHC) in endometrial cancer. This retrospective finally enrolled 100 patients, which satisfactory samples were obtained from 96 patients for liquid-based cytology and 93 patients for microtissue histology. The concordance rates with D&C, sensitivity, and specificity were 94.8%, 76.9%, and 97.5% for liquid-based cytology, 96.8%, 84.6%, and 98.8% for microtissue histology, and 99.0%, 92.3%, and 100.0% for liquid-based cytology and microtissue histology combined, respectively. The AUC of ROC curves in liquid-based cytology, microtissue histology, and the combined methods for diagnostic ability were 0.873, 0.917, and 0.962, respectively. Absence rates of MLHl, MSH2, MSH6, and PMS2 proteins were 15.3% (2/13), 0% (0/13), 7.7% (1/13), and 15.3% (2/13) in the 13 endometrial cancer samples. Liquid-based cytology and microtissue histology samples from suction curettage combined IHC are useful for endometrial cancer screening.

Association of molecular subgroups with pathological parameters in endometrial carcinomas.

The integration of molecular features into the already existing pathological classification of endometrial carcinomas will offer significant prognostic information. As the literature search reveals, there are no studies from India that have classified these carcinomas based on molecular subtypes. The aim of the study was to classify endometrial carcinomas into four subtypes based on their molecular and immunohistochemical features and to find out the association of each of these molecular subtypes with the other pathological parameters. A prospective study was done on 37 consecutive cases of fresh hysterectomy specimens, biopsy-proven as endometrial carcinomas between November 2019 and August 2020. Three immunohistochemical markers ( p53 , mismatch repair proteins, MutS homolog6 and Postmeiotic seggregation 2 respectively[ MSH6 , and PMS2] ), along with DNA (deoxyribonucleic acid) sequencing of selected regions of the POLE gene was performed in each of the 37 cases. Endometrial carcinomas were subclassified into four subtypes, and the association of each of these four subtypes with the other pathological parameters was also explored. Statistical analysis was done using the IBM Statistical Package for the Social Science (SPSS) Version 20.0 software (IBM SPSS, USA). Among the 37 cases studied, eight (21.6%) cases were p53 abnormal, eight (21.6%) cases showed MMR-D (mismatch repair deficient), one case (2.7%) showed mutation of POLE , and 21 cases (56.8%) were assembled under p53 wild-type. Higher grade endometrial carcinomas showed more (80.0%) p53 abnormal ( P < 0.001). All the p53 wild-type (100%) were of Type 1 endometrial carcinoma subtype ( P = 0.001) and low-grade type (90.5%; P = 0.005). Our study confirms that the type of carcinoma and grade correlates with p53 expression, p53 abnormal being associated with higher grade and type 2 endometrial carcinomas, whereas p53 wild-type is associated with low-grade and type 1 endometrial carcinoma. There was only one case of the POLE subtype identifiable in our study.