Mismatch repair proteins expression and tumor‑infiltrating T‑cells in colorectal cancer

Abstract

Microsatellite instability (MSI) and tumor mutational burden (TMB) are indicators of the tumor mutational load, which can lead to immune cell recruitment. By contrast, the number of tumor-infiltrating T cells (TITs) is indicative of the host immune response to tumor cells. The present study evaluated if the expression of mismatch repair (MMR) proteins can be used as a precise tool to assess immunogenicity in the tumor microenvironment. A total of 73 colorectal cancer cases were enrolled in the present study. MMR protein expression was assessed using four-antibodies immunohistochemistry (IHC) targeting MLH1, MSH2, MSH6 and PMS2. TIT was assessed through IHC by counting CD3 + and CD8 + cells in tumor. The enrolled cases were classified into four groups according to MMR and TIT status i) Mismatch repair-proficient (pMMR) and a high number of TITs (pMMR/TIT-H); ii) pMMR and a low number of TITs (pMMR/TIT-L); iii) mismatch repair-deficient (dMMR) and TIT-H (dMMR/TIT-H); and iv) dMMR/TIT-L]. The present study evaluated the clinicopathological characteristics of the four groups, in addition to the difference of TMB. TMB analysis was counted the number of the somatic mutations through multi-genes panel using next-generation sequencing. Clinicopathological characteristics, including age, sex, pathological depth of invasion and lymph node metastasis, were not found to be statistically different between dMMR/TIT-H and dMMR/TIT-L groups. Tumors among pMMR/TIT-H group were associated with poorly differentiation compared with those in pMMR/TIT-L group (P=0.025). The median TMB among the dMMR/TIT-H group was the highest in four groups but the median TMB was <10 muts/Mb in dMMR/TIT-L, pMMR/TIT-H and pMMR/TIT-L groups, respectively. However, one tumor in the pMMR/TIT-H group showed high TMB. The present findings suggest that assessing MMR status alone may not be sufficient to precisely evaluate the antitumor immune response in the tumor microenvironment.

Genetic Analyses of Primary Liver Cancer Cell Lines: Correspondence With Morphological Features of Original Tumors

“…Unstained sections were immunostained with antibodies against human mismatch repair (MMR) proteins following the method described previously (29). Briefly, the expression of MMR proteins was assessed using a four-antibody immunohistochemical assay targeting MutL homolog 1 (MLH1 clone; ES05), MutS homolog 2 (MSH2 clone; FE11), MutS homolog 6 (MSH6 clone; EP49) and post-meiotic segregation 1 homolog 2 (PMS2 clone; EP51), and the DAKO EnVision system, as previously described (29). All antibodies and detection systems were purchased from Agilent Technologies, Inc.…”

“…We reassessed the date based on fibroblast growth factor-19 (FGF-19) amplification. Detailed procedures are described in our previous report (29). Briefly, the cells (2-10×10 3 cells per well) were seeded in 96well plates (Thermo Fisher Science, Roskilde, Denmark), cultured for 24 h, and the culture medium was changed to a new medium with or without lenvatinib at 1.875, 3.75, 7.5, 15, and 30 μM.…”