pMMR Colorectal Cancer Research Articles

The risk of developing a mismatch repair deficient colorectal cancer after undergoing cholecystectomy

Objectives: Mismatch repair deficient (dMMR) colorectal cancer (CRC) is caused by inactivation of the MMR DNA repair system, most commonly via epigenetic inactivation of the MLH1 gene, and these tumors occur most frequently in the right colon. The objective was to determine whether cholecystectomy (CCY) increases the risk of a dMMR CRC by comparing CCY incidence in patients with dMMR CRC and proficient MMR (pMMR) CRC to unaffected controls.Materials and methods: All patients diagnosed with CRC in Iceland from 2000 to 2009 (n = 1171) were included. They had previously been screened for dMMR by immunohistochemistry (n = 129 were dMMR). Unaffected age- and sex-matched controls (n = 17,460) were obtained from large Icelandic cohort studies. Subjects were cross-referenced with all pathology databases in Iceland to establish who had undergone CCY. Odds ratios were calculated using unconditional logistic regression.Results: Eighteen (13.7%) dMMR CRC cases and 90 (8.7%) pMMR CRC cases had undergone CCY compared to 1532 (8.8%) controls. CCY-related odds ratios (OR) were 1.06 (95% CI 0.90–1.26, p = .577) for all CRC, 1.16 (95% CI 0.66–2.05 p = .602) for dMMR CRCand 1.04 (95% CI 0.83–1.29, p = .744) for pMMR CRC. Furthermore, OR for dMMR CRC was 0.51 (95% CI 0.16–1.67, p = .266), 2.04 (95% CI 0.92–4.50, p = .080) and 1.08 (95% CI 0.40–2.89, p = .875) <10 years, 10–20 years and >20 years after a CCY, respectively.Conclusions: There was no evidence of increased risk of developing dMMR CRC after CCY although a borderline significantly increased 2-fold risk was observed 10–20 years after CCY. Larger studies are warranted to examine this further.

Accuracy of four mononucleotide-repeat markers for the identification of DNA mismatch-repair deficiency in solid tumors

BackgroundTo screen tumors with microsatellite instability (MSI) arising due to DNA mismatch repair deficiency (dMMR), a panel of five quasi-monomorphic mononucleotide-repeat markers amplified in a multiplex PCR (Pentaplex) are commonly used. In spite of its several strengths, the pentaplex assay is not robust at detecting the loss of MSH6-deficiency (dMSH6). In order to overcome this challenge, we designed this study to develop and optimize a panel of four quasi-monomorphic mononucleotide-repeat markers (Tetraplex) for identifying solid tumors with dMMR, especially dMSH6.MethodsTo improve the sensitivity for tumors with dMMR, we established a quasi-monomorphic variant range (QMVR) of 3–4 bp for the four Tetraplex markers. Thereafter, to confirm the accuracy of this assay, we examined 317 colorectal cancer (CRC) specimens, comprising of 105 dMMR [45 MutL homolog (MLH)1-deficient, 45 MutS protein homolog (MSH)2-deficient, and 15 MSH6-deficient tumors] and 212 MMR-proficient (pMMR) tumors as a test set. In addition, we analyzed a cohort of 138 endometrial cancers (EC) by immunohistochemistry to determine MMR protein expression and validation of our new MSI assay.ResultsUsing the criteria of ≥ 1 unstable markers as MSI-positive tumor, our assay resulted in a sensitivity of 97.1% [95% confidence interval (CI) = 91.9–99.0%] for dMMR, and a specificity of 95.3% (95% CI = 91.5–97.4%) for pMMR CRC specimens. Among the 138 EC specimens, 41 were dMMR according to immunohistochemistry. Herein, our Tetraplex assay detected dMMR tumors with a sensitivity of 92.7% (95% CI = 80.6–97.5%) and a specificity of 97.9% (95% CI = 92.8–99.4%) for pMMR tumors. With respect to tumors with dMSH6, in the CRC-validation set, Tetraplex detected dMSH6 tumors with a sensitivity of 86.7% (13 of 15 dMSH6 CRCs), which was subsequently validated in the EC test set as well (sensitivity, 75.0%; 6 of 8 dMSH6 ECs).ConclusionsOur newly optimized Tetraplex system will help offer a robust and highly sensitive assay for the identification of dMMR in solid tumors.

Systemic neutrophil lymphocyte ratio and mismatch repair status in colorectal cancer patients: correlation and prognostic value.

Purpose: Mismatch repair-deficient (dMMR) colorectal cancer (CRC) is associated with increased local immune response as compared with mismatch repair-proficient (pMMR) CRC. We evaluated the relationship between MMR status and systemic inflammatory factors, including neutrophil lymphocyte ratio (NLR) and C-reactive protein (CRP). We also assessed the prognostic value of these parameters.Methods and materials: We analysed the relationship between MMR status (obtained by histochemical analysis), neutrophil and lymphocyte counts, NLR, and CRP level. The impact of systemic inflammatory factors on survival was also evaluated in dMMR and pMMR CRC patients.Results: A total of 1353 male and 892 female patients were eligible for analysis, of which, 253 patients (11.3%) were found to have dMMR status. Patients with dMMR status presented with increased neutrophil counts, and higher NLR and CRP levels in early stage CRC. In stage IV CRC patients, no correlation between MMR status and systemic inflammatory factors was found. Lymphocyte counts did not correlate with MMR status. High NLR was a prognostic factor for poor survival in pMMR CRC. However, NLR was not a prognostic factor in dMMR CRC.Conclusions: Our results suggest that dMMR CRC correlates with higher neutrophil count, NLR and CRP levels only in non-metastatic patients, and NLR has prognostic value only in pMMR CRC.

Mismatch repair–deficient colorectal cancer: a model of immunogenic and immune cell–rich tumor despite nonsignificant programmed cell death ligand-1 expression in tumor cells

Mismatch repair-deficient (dMMR) colorectal cancers (CRCs) are good responders to anti-programmed cell death ligand-1 (PD-L1) immunotherapy, but the value of PD-L1 testing remains unclear. We studied PD-L1 expression and the tumor immune microenvironment in dMMR CRC as a model of good responders to immunotherapy. We examined 35 dMMR and 34 mismatch repair-proficient (pMMR) CRCs using immune cell markers (CD3, CD4, CD8, CD20, CD68, and FOXP3) as well as programmed cell death receptor-1 (PD-1) and PD-L1 immunohistochemistry staining in whole tumor specimens and tissue microarray slides to compare 4 PD-L1 immunohistochemistry clones (SP142, E1L3N, 22C3, and 28.8). We observed no significant difference in PD-L1 expression between dMMR and pMMR CRCs. Only 2 dMMR tumors had membranous PD-L1 staining. Expression of PD-L1 was greater in stromal immune cells of dMMR CRC, which also contained more numerous intraepithelial (CD3+, CD8+, FOXP3+, and PD-1+) and stromal (CD8+, PD-1+) lymphocytes than did pMMR tumors. Immune cell quantification discriminated better between dMMR and pMMR tumors than did PD-L1 expression. Tumor heterogeneity and variations in PD-L1 expression were noted with different antibodies, especially for PD-L1+ immune cells, which were more numerous at the invasion margin. Given the poor correlation with mismatch repair status and technical limitations, the value of PD-L1 testing to accompany the development of anti-PD-1/PD-L1 immunotherapy remains unclear. Further clinical trials are required to determine which parameters are valuable predictive biomarkers of the response to immunotherapy among mismatch repair status, PD-L1 expression, and immune cell quantification in CRC.

Early genetic aberrations in patients with sporadic colorectal cancer.

Chromosome instability (CIN) is widely observed in both sporadic and hereditary colorectal cancer (CRC). Defects in APC and WNT signaling are primarily associated with CIN in hereditary CRC, but the genetic causes for CIN in sporadic CRC remain elusive. Using high-density SNP array and exome data from The Cancer Genome Atlas (TCGA), we characterized loss of heterozygosity (LOH) and copy number variation (CNV) in the peripheral blood, normal colon, and corresponding tumor tissue in 15 CRC patients with proficient mismatch repair (MMR) and 24 CRC patients with deficient MMR. We found a high frequency of 18q LOH in tumors and arm-specific enrichment of genetic aberrations on 18q in the normal colon (primarily copy neutral LOH) and blood (primarily copy gain). These aberrations were specific to the sporadic, pMMR CRC. Though in tumor samples genetic aberrations were observed for genes commonly mutated in hereditary CRC (eg, APC, CTNNB1, SMAD4, BRAF), none of them showed LOH or CNV in the normal colon or blood. DCC located on 18q21.1 topped the list of genes with genetic aberrations in the tumor. In an independent cohort of 13 patients subjected to Whole Genome Sequencing (WGS), we found LOH and CNV on 18q in adenomatous polyp and tumor tissues. Our data suggests that patients with sporadic CRC may have genetic aberrations preferentially enriched on 18q in their blood, normal colon epithelium, and non-malignant polyp lesions that may prove useful as a clinical marker for sporadic CRC detection and risk assessment.