Mismatch repair deficiency is strongly associated with responsiveness to anti-PD-1 in other cancers and can be detected using immunohistochemistry for MLH1, MSH2, MHS6, and PMS2.
By immunohistochemistry and molecular studies, we detected mismatch repair protein deficiency, microsatellite instability (MSI) and MLH1 promoter methylation in the derived carcinoma, but not in the benign teratoma, indicating mismatch repair deficiency was implicated in the process of malignant transformation.
Mismatch repair deficiency was associated with tumor development and progression therefore, current study was aimed to investigate MLH1 and MSH2 expression in breast cancer and correlate patients' clinicopathological factors with status of mismatch repair genes.
In a proof-of-concept study delayed tumorigenesis and prolonged survival has been shown in a clinically-relevant mouse model for MMR-D-related diseases (=MLH1 knock out mice).
Biallelic germline mutations in the DNA mismatch repair gene MLH1 lead to constitutional mismatch repair-deficiency syndrome and an increased risk for childhood hematopoietic malignancies, including lymphoma and leukemia.
Interestingly, after identification of its mismatch repair-deficiency (MLH1/PMS2-absent, MSH2/MSH6-intact), pembrolizumab-based immunotherapy was initiated, leading to a marked clinical response.
Lesions of both sites showed a DNA mismatch repair deficiency with immunohistochemical loss of MLH1 and PMS2 expression without MLH1 promoter hypermethylation.
Patients whose tumors showed MMR deficiency (MMR-D) and wild-type BRAF were selected to undergo mutational analysis of the MLH1 and MSH2 genes using Sanger sequencing.
Universal tumor screening for LS is routinely performed on colon cancer, and screening has identified patients with unexplained MMR deficiency that lack MLH1 methylation and a germline mutation.
Tumors with MMR abnormalities by IHC or MSI and MLH1 methylation were classified as epigenetic MMR deficiency while those without MLH1 methylation were classified as probable MMR mutations.
Our findings have clinical relevance regarding therapeutic targeting of BRCA2 vulnerabilities, EGFR mutations or other identified oncogenic drivers such as NTRK in MSH2/MLH1-mutant CRCs or other tumors with mismatch repair deficiency.
Constitutional mismatch repair deficiency syndrome is a cancer predisposition syndrome caused by autosomal recessive biallelic (homozygous) germline mutations in the mismatch repair genes (MLH1, MSH2, MSH6, and PMS2).
We identified dMMR CRC resected at Ohio State University from 1999 to 2013 and stained a corresponding metastasis for all four MMR proteins (MLH1, MSH2, MSH6, PMS2) with IHC.
This study provides statistical evidence that MMR deficiency is correlated with hypermethylation of hMLH1 promoter and upregulation of hsa-miR-155, hsa-miR-141 and hsa-miR-21 in prostate cancer.
Thus, a case with the clinical condition of hereditary non-polyposis colorectal cancer as defined by the Amsterdam criteria may be one of Lynch syndrome characterized by a germline defect in one of the several MMR genes, one of the yet-to-be-defined "Lynch-like syndrome" if there is evidence of MMR deficiency in the tumor but no detectable germline MMR defect or tumor MLH1 promoter methylation, or "familial colorectal cancer type X" if there is no evidence of MMR deficiency.
This study compared two biomarkers in tumours with mismatch repair deficiency; quantification of methylation of the MLH1 promoter region using a novel assay and BRAF c.1799T>A, p.(Val600Glu) mutation status in the identification of constitutional mutations.
Tumor MMR-deficiency was observed for 22 cases [69 %; 95 % confidence interval (CI) 50-83 %], with the highest prevalence of MMR-deficiency in tumors from MSH2 mutation carriers (19/23, 83 %) compared with MLH1 and MSH6 carriers combined (3/9, 33 %; p = 0.01).