Mismatch repair deficiency screening in colorectal carcinoma by a four-antibody immunohistochemical panel in Pakistani population and its correlation with histopathological parameters

Mismatch Repair Deficient (dMMR) Colorectal Carcinoma in a Pakistani Cohort: Association With Clinical and Pathological Parameters

Introduction Microsatellite instability (MSI) is an important pathway in colorectal carcinoma (CRC) pathogenesis. MSI occurs due to mutations in mismatch repair (MMR) genes that include MutL protein homolog 1 (MLH1), postmeiotic segregation increased 2 (PMS2), MutS homolog 2 (MSH2), and MutS homolog 6 (MSH6). CRC with MSI is termed MMR deficient (dMMR) CRC. Conversely, CRC with intact MMR genes is called microsatellite stable (MSS) or MMR proficient (pMMR). In this study, we compared the clinicopathological features of dMMR CRC with pMMR CRC. Methods It was a retrospective study conducted in the Department of Histopathology, Liaquat National Hospital, Karachi, Pakistan, from March 2020 to February 2022, over a duration of two years. Biopsy-proven cases of CRC with upfront surgical resection were included in the study. Microscopic examination was performed to evaluate tumor type, grade, and extent of invasion, presence of necrosis, perineural invasion (PNI), lymphovascular invasion (LVI), peritumoral lymphocytes (PTL), intratumoral lymphocytes (ITL), and nodal metastasis. Immunohistochemical staining was performed using antibodies, namely, MLH1, PMS2, MSH2, and MSH6. Any loss of nuclear expression in tumor cells was termed dMMR or microsatellite instable, whereas the intact nuclear expression in tumor cells was labeled as MSS or pMMR. Results A total of 135 cases of CRC were included in the study. The mean age at diagnosis was 46.76 ± 17.74 years, with female predominance (60.7%). The loss of MLH1, PMS2, MSH2, and MSH6 expression was noted in 39.3%, 34.1%, 17.8%, and 16.3% cases, respectively. Overall, 59.3% of CRCs were pMMR, while 40.7% were dMMR. A significant association of MMR status was noted with respect to age, PNI, LVI, tumor grade, tumor (T) and nodal (N) stage, mucinous differentiation, and ITL. dMMR CRC was significantly above 50 years than pMMR CRC. The frequency of PNI and LVI was lower in dMMR CRC than in pMMR CRC. Conversely, the higher grade (grade 3) and higher T-stage (T4) were associated with dMMR CRC. Alternatively, the frequency of higher N stage (N2b) was more commonly seen in pMMR CRC. Moreover, mucinous differentiation and ITL were significantly associated with dMMR CRC. Conclusion A significant proportion of CRC patients in our population demonstrated dMMR status. dMMR CRC had a higher histological grade with a higher frequency of mucinous differentiation and higher T-stage. Conversely, the presence of LVI, PNI, and higher N stages were associated with pMMR CRC.

Early-Onset/Young-Onset Colorectal Carcinoma: A Comparative Analysis of Morphological Features and Biomarker Profile

Introduction Colorectal carcinoma (CRC) is one of the most common cancers that involve the human body. Young-onset CRC (YO-CRC) or early-onset CRC (EO-CRC) is defined as CRC that develops before the age of 50 years, as opposed to CRC that is diagnosed after the age of 50, referred to as late-onset CRC (LO-CRC). EO-CRC is sparsely studied in our population. Therefore, in this study, we evaluated the clinicopathological parameters and biomarker profile of EO-CRC and compared them with those of LO-CRC. Methods This was a retrospective study conducted at the Department of Histopathology, Liaquat National Hospital, Karachi, Pakistan. A total of 254 biopsy-proven cases of CRC, reported over a period of nine years, were enrolled in the study. The specimens collected during surgery were sent to the laboratory for histopathological and immunohistochemical (IHC) status examinations. IHC staining of the specimens was performed using antibodies, namely, MutL protein homolog 1 (MLH1), postmeiotic segregation increased 2 (PMS2), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6), and human epidermal growth factor receptor 2 (HER2/neu), on representative tissue blocks. A comparison of morphological and biomarker profiles between EO-CRC and LO-CRC was performed. Results The mean age at diagnosis was 46.27±17.75 years, with female predominance (59.8%). A significant difference between the two groups (EO-CRC and LO-CRC) was noted with respect to laterality, tumor site, tumor grade, tumor type, presence of pre-existing polyps, perineural invasion (PNI), lymphovascular invasion (LVI), and IHC markers. EO-CRC (as opposed to LO-CRC) significantly affected the left colon (92.6% vs. 72.9%, p<0.001), with the rectosigmoid being the most common site in the majority of cases (72.1% in EO-CRC vs. 61% in LO-CRC). EO-CRC showed a higher frequency of PNI and LVI than LO-CRC (42.6% vs. 23.7%, p=0.001; 29.4% vs. 18.6%, p=0.046, respectively). A significantly higher proportion of EO-CRCs were mucinous (42.6%) and medullary carcinoma (11.8%). Although the majority (54.4%) of cases of EO-CRC were grade 2 tumors at the time of diagnosis, a significantly higher proportion of them were grade 3 (44.1%) compared with LO-CRC. IHC comparisons between the two age groups showed that a significantly higher proportion of cases of EO-CRC showed positive HER2/neu expression (27.1%) compared with LO-CRC (13.2%). Conversely, the loss of expression of microsatellite instability (MSI) markers was more commonly seen in LO-CRS compared with EO-CRC. Conclusions We found a relatively higher frequency of EO-CRC in our population. Moreover, compared with LO-CRCs, EO-CRCs were associated with prognostically poor histological parameters, such as mucinous and medullary carcinoma, high-grade, PNI, and LVI. Similarly, EO-CRC had a higher positive expression of HER2/neu with intact MSI markers compared with AO-CRC; all these characteristics indicate poor biological behavior in EO-CRC.

Potential predictors for CDX2 expression loss and mismatch repair deficiency in colorectal cancer

CDX2 expression loss is commonly associated with mismatch repair deficiency (dMMR) in colorectal cancer (CRC). However, there are only a few studies that have attempted to correlate CDX2 expression loss with specific MMR genes (MLH1, MSH2, MSH6, PMS2). This is a retrospective study of 327 patients who underwent surgery due to CRC. Nine patients (2.9%) had two synchronous CRCs, making the total sample 336 CRC. Histopathological data such as tumor type, tumor grade, perineural, lymphatic, and vascular invasion, pT stage, pN stage, peritumoral and intratumoral lymphocytic infiltration were collected and recorded in the database. After immunohistochemical analysis, CDX2 expression, MLH1, MSH2, MSH6, and PMS2 deficiency were also recorded. CDX2 expression loss was detected in 19 out of 336 CRCs (5.9%) and was associated with ascending colon CRC, partially mucinous adenocarcinoma, poorly differentiated carcinoma, and dMMR. Forty-four (13.1%) of CRCs were dMMR. We found a statistically significant association between CDX2 expression loss and MLH1 and PMS2 deficiency. Considering that most expression phenotypes include pairs of MMR genes, we analyzed MLH1/PMS2 and MSH2/MSH6 as heterodimers. Analysis of heterodimers showed a similar result, namely, that MLH1/PMS2 heterodimer deficiency was significantly associated with CDX2 expression loss. We also constructed a regression model for CDX2 expression loss and for dMMR. Poor tumor differentiation and MLH1/PMS2 heterodimer deficiency have been identified as potential predictors for CDX2 expression loss. CRC in the ascending colon and CDX2 expression loss have been identified as positive potential predictors of dMMR with rectal cancer as negative potential predictor of dMMR. Our study showed a significant association between CDX2 expression loss and MLH1 and PMS2 deficiency in CRC. We also managed to produce a regression model for CDX2 expression and showed that poor tumor differentiation and MLH1/PMS2 heterodimer deficiency are independent factors for CDX2 expression loss. We were the first to include CDX2 expression in a regression model for dMMR and showed that CDX2 expression loss can be used as a predictive factor for dMMR, which should be confirmed by further studies.

Expression of DNA mismatch repair proteins in melanoma patients treated with immune checkpoint inhibitors

PURPOSE

To investigate the protein expression of DNA mismatch repair (MMR) proteins in patients with cutaneous melanoma (CM) under immune checkpoint inhibitor (ICI) therapy.

METHODS

Immunohistochemistry was performed on tumor tissue for MMR proteins MLH1, MSH2, MSH6, and PMS2 in 50 metastatic CM patients treated with ICI (ipilimumab, nivolumab, pembrolizumab).

RESULTS

Best overall response (BOR) rate was 48% (24/50). Reduced MMR protein expression (nuclear expression in < 80% of tumor cells) was observed in 8 patients (16%). Compared to other clinical parameters, baseline neutrophil/lymphocyte ratio and reduced intratumoral MMR protein expression (P = 0.0033) were determined as the only parameters significantly associated with favorable BOR. However, in this small study population, reduced MMR protein expression did not reach statistical significance in multivariate analysis.

CONCLUSION

Reduced MMR protein expression is observed in CM and might predict favorable BOR in patients treated with ICI, as was observed for other entities. However, these findings need to be substantiated in larger patient cohorts.

An Evaluation of the Immunohistochemical Expression of Mismatch Repair Proteins (MSH2, MSH6, MLH1, and PMS2) in Prostate Adenocarcinoma

Background and objective

Mismatch repair (MMR) proteins are an integral part of the cell cycle, and they play an important role in the genomic stability of the microsatellite complex. Microsatellite instability (MSI) is associated with Lynch and multi-tumor syndromes. Identifying patients with Lynch syndrome is essential for screening, early detection, and surveillance of other Lynch syndrome-associated tumors. The role of MMR deficiency is well known in colorectal and endometrial adenocarcinoma. However, the role of MMR deficiency in prostatic adenocarcinoma is a matter of controversy. A few studies have been published to analyze the association between MMR deficiency and prostatic adenocarcinoma. In this study, we used immunohistochemistry to look into the expression of four MMR proteins in prostatic adenocarcinoma: MSH2, MSH6, MLH1, and PMS2.

Methodology

This was a cross-sectional descriptive study involving 74 cases of acinar prostatic adenocarcinoma, diagnosed with hematoxylin & eosin (H&E), over a period of six months between December 2021 and May 2022 at the Chughtai Institute of Pathology in Lahore, Pakistan. We performed the immunohistochemical (IHC) analysis and interpretation of four antibodies, i.e., MSH2, MSH6, MLH1, and PMS2.

Results

In our study, the age of the patients ranged from 50 to 98 years, with a mean age of 67.99 ± 9.59 years. The specimens were collected through transurethral resection of the prostate (TURP), transurethral vaporization of the prostate (TVP), core biopsy, and radical prostatectomy. Isolated loss of each MSH2 and PMS2 was noted in nine cases (12.20%) and MSH6 in two cases (2.70%). There was no loss noted for MLH1. Furthermore, simultaneous loss of MSH2/MSH6 was observed in one case (1.35%).

Conclusion

Our study findings revealed a low frequency of IHC expression of MMR proteins, especially the concurrent loss of paired MMR proteins. However, prostatic adenocarcinoma is associated with the isolated loss of MMR proteins. Thus, the present study does not warrant reflex testing/screening in every case of prostatic adenocarcinoma, because of its low frequency, which is probably suggestive of its sporadic pattern.

The Molecular Associations of Signet-Ring Cell Carcinoma in Colorectum: Meta-Analysis and System Review

Background: Signet ring cell carcinoma (SC) accounts for 1% of total colorectal cancer (CRC) cases and is associated with aggressive behaviors, such as lymphatic invasion and distant metastases, resulting in poor prognosis. To date, there is still a lack of consensus on the genetic etiology underpinning this cancer subtype. This study aimed to clarify the molecular associations of SC by using meta-analysis and a systematic review. Methods: PubMed, Embase, and Cochrane Library were searched for studies evaluating the KRAS, BRAF, P53 statuses, and microsatellite instability (MSI) in CRC patients with different histological subtypes, including SC. The diagnosis of SC is defined as the signet ring cells comprising ≥50 percent of the tumor mass. By dividing the studies into subgroups based on the composition of control groups, such as classic adenocarcinoma (AC; no SC components) and non-SC (including those with SC components < 50%), the relative risk (RR) of molecular alterations for SC in each study were pooled using a random-effects model. Two reviewers identified trials for inclusion, assessed quality, and extracted data independently. Results: Data from 29 studies consisting of 9366 patients were included in this analysis. SC was associated positively with MSI (RR 1.78, 95% CI 1.34 to 2.37; 95% CI 0.77 to 4.15; p = 0.0005), BRAF mutation (RR 1.99, 95% CI 1.21 to 3.26; 95%CI 0.68 to 5.82; p = 0.0146), and negatively with KRAS mutation (RR 0.48, 95% CI 0.29 to 0.78; 95% CI 0.09 to 2.49; p = 0.0062). No association was found between SC and P53 expression (RR 0.92, 95% CI 0.76 to 1.13; 95%CI 0.61 to 1.39; p = 0.3790). Moreover, it was associated negatively with P53 gene mutations (RR 0.92, 95% CI 0.77 to 1.09; 95% CI 0.46 to 1.82; p = 0.1568), and P53 protein (RR 0.93, 95% CI 0.58 to 1.49; 95% CI 0.40 to 2.17; p = 0.6885). Conclusions: The molecular etiology of SC may be associated with the BRAF and MSI pathways. Its features, such as the high frequency of BRAF mutation, could partly explain its less favorable outcomes and limited effects of traditional chemotherapy.

Expression of Mismatch Repair Proteins in Merkel Cell Carcinoma

Simple Summary

Merkel cell carcinoma (MCC) is a rare and highly malignant skin cancer with neuroendocrine differentiation. About 80% are Merkel cell polyomavirus (MCPyV) positive. The aim of this work was to immunohistochemically investigate the expression of mismatch repair proteins (MSH2, MSH6, MLH1, and PMS2) in MCC (n = 56). In a second step, tumors with a low expression were tested for microsatellite instability. Microsatellite instability in MCC could have an impact on immune checkpoint inhibitor therapy (ICI) outcome. This study showed a significant association between low expression of mismatch repair proteins and a negative MCPyV status. Microsatellite instability was detected in only one case. Future studies will establish whether this subset of MCC patients respond better to ICI.

Abstract

We aimed to assess for the first time the mismatch repair (MMR) protein expression in Merkel cell carcinoma (MCC). Immunohistochemistry was performed for MLH1, MSH2, MSH6, and PMS2 on patients’ tumor tissue (n = 56), including neighbored healthy control tissue. In cases with low-level MMR expression (<10th percentile), we performed multiplex PCR in combination with high-resolution capillary electrophoresis in order to confirm microsatellite instability (MSI). Microscopic evaluation revealed a high median expression for all MMR proteins studied (91.6–96.3%). However, six patients (56/10.7%) had low-level MLH1 expression, six (55/10.9%) had low-level MSH2 expression, five (56/8.9%) had low-level MSH6 expression, and six (54/11.1%) had low-level PMS2 expression. Together, we observed nine (56/16.1%) patients who had low-level MMR expression of at least one protein. Of the patients with low-level MMR expression, MSI evaluation was possible in five cases, revealing one case with high-level MSI. In all MMR proteins assessed, low-level expression was significantly (p = 0.0004 to p < 0.0001) associated with a negative Merkel cell polyomavirus (MCPyV) status. However, the expression profiles of the MMR proteins did not correlate with clinical outcome measures such as disease relapse or death (p > 0.05). MCC appears to be a malignancy characterized by low-level MMR rather than completely deficient MMR in a subset of cases, predominantly affecting MCPyV-negative tumors. Future studies will establish whether this subset of MCC patients respond better to immune checkpoint inhibitor therapy.

Assessment of mismatch repair deficiency, CDX2, beta-catenin and E-cadherin expression in colon cancer: molecular characteristics and impact on prognosis and survival - an immunohistochemical study

Microsatellite instability (MSI) or the deficiency of mismatch repair (MMR) proteins is one of the molecular pathways of colorectal tumorigenesis and may have important clinical implications in predicting the treatment response. We evaluated the relationship between clinicopathological features and MMR proteins [mutL homologue 1 (MLH1), mutS homologue 2 (MSH2), mutS homologue 6 (MSH6), postmeiotic segregation increased 2 (PMS2)], adhesion molecules (E-cadherin, beta-catenin) and caudal-type homeobox 2 (CDX2) in 31 patients with colon adenocarcinoma, using immunohistochemistry. We also aimed to assess the prognostic value of the studied proteins. MLH1 loss was correlated to PMS2 loss (p=0.006) and MSH2 loss (p=0.023); MSH2 loss was significantly associated to MSH6 loss (p=0.011). Tumors with MSH6 loss, together with tumors with PMS2 loss, covered all the patients with MSI status. We found a significant correlation between MSI tumors and mucinous histological type (p=0.03), but no significant associations with other clinicopathological features or with survival rate. There was a significant correlation between E-cadherin expression and differentiation degree (p=0.018) and between beta-catenin expression and lymph node invasion (p=0.046). No significant association between CDX2 loss and any clinical or pathological features was found (p>0.05). No significant differences were identified in overall survival according to E-cadherin, beta-catenin or CDX2 expression (p>0.05). In our study, PMS2 loss was significantly correlated with CDX2 loss (p=0.03). In conclusion, the molecular analysis of biological markers for colon cancer may be important for patient stratification, in order to select the optimal treatment algorithm. Our results suggest that probably the double panel (MSH6 and PMS2) is enough to detect the MSI status, instead of using the quadruple panel.

Clinicopathologic Factors Associated with Mismatch Repair Status Among Filipino Patients with Young-Onset Colorectal Cancer

Introduction

Young-onset colorectal cancer is recognized as a distinct disease that may be sporadic or hereditary in nature. Microsatellite instability testing is recommended as a routine procedure in evaluating colorectal cancer specimens, especially in young-onset disease, because of implications in management. Immunohistochemistry of mismatch repair proteins serves as an inexpensive alternative to microsatellite instability testing with the added advantage of monitoring protein expression levels that may suggest underlying genetic or epigenetic alterations. This descriptive study aimed to determine the frequencies of proficient and deficient mismatch repair status among Filipino young-onset colorectal cancer patients, and to investigate their clinicopathologic profile.

Methods

Tumor tissues were prospectively collected from patients from two tertiary hospitals in the Philippines. Patients of age ≤45 years with resected adenocarcinoma of the colon or rectum were recruited.

Results

Seventy-seven out of 124 patients had tumor samples sent for immunohistochemistry. Of these, 61 samples (79%) were found to have proficient status while 16 samples (21%) had deficient status. Mismatch repair protein deficiencies, when present, more commonly involved MSH2 and MSH6 (9%) rather than MLH1 and PMS2 (5%). The deficient group had a mean age of 37.1 years and a female preponderance (56.25%), presenting as locally advanced ascending or descending colon tumors with mucinous histology in half of the population. The mismatch repair proficient group presented as locally advanced rectal and sigmoid tumors but with fewer mucinous adenocarcinomas (26.2%) compared to the deficient group. In both the mismatch repair proficient and deficient patients with family history reports, most did not have any known relative with cancer (75.4% and 68.75%, respectively).

Conclusion

This is the first attempt to perform mismatch repair testing among young-onset colorectal cancer patients in the Philippines and to gather data on their clinicopathologic characteristics. However, the limited sample size precludes conclusive results for the associations of mismatch repair with clinicopathologic features.

Prognostic Value and Immunohistochemical Analysis of Mismatch Repair Deficiency in Patients with Stage II and III Colorectal Carcinoma-A Single-Center Study

Background and objectives: Deficient mismatch repair (MMR) status is associated with good prognosis but poor therapeutic response to adjuvant chemotherapy in patients with colorectal cancer. However, there are some opposed arguments considering therapeutic outcomes in patients with evidenced MMR deficiency in colorectal cancer. The aim of the study was the investigation of prognostic value and immunohistochemical analysis of the MMR-deficiency tumors. Materials and Methods: The study enrolled 104 patients with resected stage II and III colorectal cancer samples from the period 2018–2019. Results: The tumors with deficient MMR status were significantly associated with age up to 50 years and right-sided localization (p < 0.001). During the follow-up period of 22.43 ± 6.66 months, 21 patients (20.2%) died, whereas 14 patients (13.5%) had relapses. The loss of mutL homologue 1/postmeiotic segregation increased 2 (MLH1/PMS2) expression, compared to proficient MMR tumors, was associated with shorter disease-free survival in patients with lymphovascular invasion (p < 0.05), perineural invasion (p < 0.01), stage III (p < 0.05) and high-grade tumor (p < 0.05). Conclusions: This retrospective pilot study of a single-center cohort of patients with stage II and III colorectal cancer highlights the clinical importance of using immunohistochemistry (IHC) analysis as a guide for diagnostic algorithm in a country with limited resources, but with a high prevalence of colorectal carcinoma in the young patients. MMR-deficiency tumors compared with proficient MMR colorectal cancer was not shown to be a significant predictor of disease-free and overall survival.

Worldwide variation in lynch syndrome screening: case for universal screening in low colorectal cancer prevalence areas

To perform a systematic assessment of universal Lynch syndrome (LS) screening yield in colorectal cancer (CRC) patients around the world. Universal screening for LS is recommended in all CRC patients. However, the variation in yield of LS screening in the setting of significant global variation in CRC prevalence is unknown. A systematic review of articles in the MEDLINE database was performed to identify studies performing universal screening for LS. All cases with microsatellite instability (MSI-H) or missing one or more proteins on immunohistochemistry (IHC) were considered screening positive. The overall pooled yield of universal LS screening in 97 study arms from 89 identified studies was 11.9% (5649/47545) and the overall pooled percentage of confirmed LS patients was 1.8% (682/37220). LS screening positivity varied significantly based on geographic region (Kruskal Wallis test, p < 0.001) and reported 5-year CRC prevalence in the country (Fisher's exact, p < 0.001). Significant inverse correlation was found between LS screening positivity and 5-year CRC prevalence (Pearson correlation, r =  - 0.56, p < 0.001). The overall yield of LS screening was 15.00% (382/2553) and rate of confirmed LS was 7.7% (113/1475) in LS screening done in patients ≤ 50 years (16 studies). There is significant geographic variation in LS screening positivity with higher yield in countries with lower prevalence of CRC. Our results highlight the importance of universal LS screening in younger patients and low CRC prevalence countries.

Clinicopathologic characteristics of resectable colorectal cancer with mismatch repair protein defects in Chinese population: Retrospective case series and literature review

Colorectal cancer (CRC) represents a major malignancy globally, with microsatellite instability as its second top molecular mechanism of carcinogenesis. Immunohistochemical (IHC), whose sensitivity and specificity exceed 90%, is used routinely to detect 4 MMR proteins (MLH1, PMS2, MSH2, and MSH6) for screening mismatch repair system defects. We aimed to assess associations of clinicopathologic characteristics with MMR status in resectable CRC patients.Stage I-III CRC cases administered surgical resection in Zhejiang Cancer Hospital in 2013 to 2015 were retrospectively analyzed. MLH1, MSH2, MSH6, and PMS2 protein amounts were evaluated immunohistochemically. Clinicopathological information, including age, sex, tumor location, histological subclass, disease stage, regional lymph node (LN) metastasis, American Joint Committee on Cancer (AJCC) 8th edition stage, and survival data were retrospectively reviewed.A total of 133 CRC cases were assessed, including 74 (55.6%), 45 (33.8%), 55 (41.4%), and 77 (57.9%) not expressing MLH1, MSH2, MSH6, and PMS2, respectively. There were significant associations of MLH1, MSH2, MSH6, and PMS2 proteins with age and sex (P < .05). MLH1, MSH2, and MSH6 (but not PMS2) showed positive associations with primary tumor location (P < .05). Of the 133 patients, 70 and 63 cases were affected on the right and left sides, respectively; significant associations of primary site with age and sex were observed (P < .05). Regarding the MMR status, MLH1, MSH2, and MSH6 protein expression levels were positively associated with primary site (P < .05). Five-year overall survival (OS) rates were 84.2% and 79.2% in left-side and right-side cases, respectively; 5-year disease-free survival (DFS) rates were 74.0% and 69.8%, respectively. Survival had no differences between left- and right-side patients in terms of OS (P = .318) and DFS (P = .481).These data demonstrate that 4 major dMMR proteins are expressed differently in left- and right-side CRCs, and survival is comparable in right- and left-side resectable CRC cases with dMMR.

TROP2 increases growth and metastasis of human oral squamous cell carcinoma through activation of the PI3K/Akt signaling pathway

Most malignant neoplasms of the oral cavity are oral squamous cell carcinoma (OSCC), which is a type of highly malignant tumor with a propensity for forming distant metastases. Trophoblast cell surface antigen 2 (TROP2) is a transmembrane protein that is overexpressed in several types of tumor cells, although its role and regulatory mechanism in OSCC have not been determined. The aim of the present study was to examine the effects of TROP2 in human OSCC cell lines. The present study demonstrated that TROP2 protein expression was upregulated in OSCC cell lines. Transfection of short hairpin RNA (shRNA) targeting TROP2 (sh‑TROP2) reduced cell proliferation, migration and invasion of OSCC cell lines, whereas overexpression of TROP2 increased proliferation, migration and invasion. sh‑TROP2 transfection in OSCC cell lines inhibited tumor growth in OSCC mouse models. Furthermore, TROP2 expression activated the phosphoinositide 3‑kinase (PI3K)/Akt signaling pathway in human OSCC cells. These results suggest that TROP2 induces cell growth, migration and invasion through activation of the PI3K/Akt signaling pathway in OSCC cells.

Microsatellite Instability in Endometrial Carcinoma by Immunohistochemistry, Association with Clinical and Histopathologic Parameters

Objective: We aimed to investigate the frequency of microsatellite instability (MSI) in endometrial carcinoma in our population and its association with clinico-pathologic features. Methods: A total of 126 cases of primary endometrial carcinoma were included in the study that underwent surgical resections. All slides of these cases were reviewed and representative paraffin fixed tissue blocks were selected for MLH1, MSH2, MSH6 and PMS2 IHC staining. IHC expression was categorized into five groups: no loss of expression; loss of expression of all four antibodies; combined loss of MLH1/PMS2; combined loss of MSH2/MSH6; and isolated loss of MLH1. Pathological records of all cases were retrieved from patient files. Result: Abnormal expression of MSI was noted in 56 cases (44.4%) among which 16 cases showed loss of nuclear expression of all markers, 34 cases showed loss of MLH1/PMS2 expression, 4 cases showed loss of MSH2/MSH6 while only 2 cases revealed isolated loss of MLH. Personal and family history suggestive of inherited cancer susceptibility was revealed in 11 cases most of which were associated with MSH2/MSH6 loss. Significant association of MSI expression was found with tumor stage and personal/family history of endometrial/ colon cancer. Conclusion: A high frequency of endometrioid cancers in our study showed abnormal expression of MSI markers, most of which depicted MLH1/PMS2 loss and were not associated with inherited cancer susceptibility. On the other hand, a minority of cases showed loss of all MSI markers or MSH2/MSH6 loss and were significantly associated with family/personal history of cancer. Therefore, we suggest that epigenetic changes in MLH1 locus may be a predominant pathway of tumorigenesis in our population rather than inherited mutation of MSI genes; however more large scale studies with genetic testing are required to validate this observation.

Additional loss of MSH2 and MSH6 expression in sporadic deficient mismatch repair colorectal cancer due to MLH1 promoter hypermethylation

Colorectal cancer (CRC) is common with 3% of cases associated with germline mutations in the mismatch repair pathway characteristic of Lynch syndrome (LS). The UK National Institute for Health and Care Excellence recommends screening for LS in all patients newly diagnosed with CRC, irrespective of age. The Yorkshire Cancer Research Bowel Cancer Improvement Programme includes a regional LS screening service for all new diagnoses of CRC. In the first 829 cases screened, 80 cases showed deficient mismatch repair (dMMR) including four cases showing areas with loss of expression of all four mismatch repair proteins by immunohistochemistry. The cases demonstrated diffuse MLH1 loss associated with BRAF mutations and MLH1 promoter hypermethylation in keeping with sporadic dMMR, with presumed additional double hit mutations in MSH2+/-MSH6 rather than underlying LS. Recognition and accurate interpretation of this unusual phenotype is important to prevent unnecessary referrals to clinical genetics and associated patient anxiety.

Immunohistochemical Expression of MMR Proteins with Clinicopathological Correlation in Colorectal Cancer in Egypt

BACKGROUND:

Microsatellite instability (MSI) is the genetic pathway underlying 15% of sporadic colorectal carcinoma (CRC) and hereditary non-polyposis CRC. MSI-H CRC has a distinct clinicopathological characteristic including excess mucin and signet ring component, proximal colon, Crohn’s like reaction, lymphocytic infiltration, and better survival.

AIM:

This research aims to screen Egyptian CRC patients for MSI status by IHC testing of expression of the MMR proteins in correlation to its clinicopathological features.

MATERIAL AND METHODS:

Immunohistochemistry study for mismatch repair proteins (MMR) was done on 115 cases of CRC. Their expressions were assessed and correlated to clinicopathological parameters in an attempt to obtain the most significant predictors of MSI.

RESULTS:

MSI (low and high) represents 67% of the study cases. The most frequent expression pattern was combined loss of MLH, and PMS2 (38% of MSI) followed by a combined loss of MSH2, and MSH6 (29% of MSI). There was significant correlation of expression pattern of MMR proteins with the laterality, lymphovascular emboli, perineural invasion, grade, T stage, N stage, signet ring component, tumor infiltrating lymphocyte, and peritumoral lesion (0.014, 0.035, 0.012, 0.033, 0.013, 0.000, 0.041, 0.012, and 0.009 respectively). Proximal location (right sided) and lower grade, higher nodal stage, and marked TIL were selected as predictors of MS-H CRC (0.005, 0.031, 0.025, and 0.000 respectively).

CONCLUSION:

All clinicopathological and histological parameters should be assessed in CRC for the sake of predicting MSI. The optimal approach to MSI evaluation is (IHC) assessment of MMR proteins.

Mismatch repair status and high expression of PD-L1 in nasopharyngeal carcinoma

Purpose

To analyze the mismatch repair (MMR) status and PD-L1 expression in nasopharyngeal carcinoma (NPC), and investigate whether PD-L1 and MMR status could be used as a biomarker for predicting response of immune checkpoint blockades (ICBs) treatment.

Patients and methods

A total of 108 patients were initially histopathologically diagnosed with NPC between December 2017 and September 2018. All tissue specimens were collected before any treatment. Tumor tissue MMR status was determined by both immunohistochemistry and PCR. The expression of PD-L1 in NPC tissue was analyzed immunohistochemically. High PD-L1 expression in tumor cells (TC) or tumor-infiltrating immune cells (TIIC) was defined as ≥50% of corresponding cells with membranous staining.

Results

Tissue samples were obtained from 102 patients after written informed consent was obtained. Seventy-one (69.6%) patients were treated in our hospital after diagnosis. Disease in stages I-III accounted for 35 (49.3%) cases, while stage IVa-IVb was identified in 36 (50.7%) cases. Only two of 102 patients were identified as MMR-deficient (dMMR) by IHC and PCR. High PD-L1 expression in TC was confirmed in 77 of the 102 (75.5%) NPC cases, while only 13 of the 102 (12.7%) NPC cases were considered to exhibit high PD-L1 expression in TIIC. PD-L1 expression in TC was positively correlated with T stage (P=0.033), while PD-L1 expression in TIIC was negatively associated with plasma Epstein-Barr virus DNA load (P=0.021), N stage (P=0.009), M stage (P=0.014), and clinical stage (P=0.001).

Conclusion

dMMR is a rare event in NPC and may not be a prospective biomarker to predict the effectiveness of treatment with ICBs in clinical practice. It was also determined that high PD-L1 expression in NPC is quite common and the importance of distinguishing PD-L1 expression in TC and TIIC was highlighted.