Cytotoxic CD8+ T cells and tissue resident memory cells in colorectal cancer based on microsatellite instability and BRAF status

BACKGROUND Recent studies in non-colorectal malignancy have associated T resident memory(T_(RM)) cells with improved patient survival. It is unknown if T_(RM) plays a role in colorectal cancer(CRC).AIM To examine the potential role of T_(RM) cells in providing immunogenicity in CRC stratified by microsatellite instability(MSI) and BRAF status.METHODS Patients with known MSI and BRAF mutation status were eligible for inclusion in this study. CRC tumour sections stained with haematoxylin and eosin were microscopically reviewed and the images scanned prior to assessment for location of invading edge and core of tumour. Sequential sections were prepared for quantitative multiplex immunohistochemistry(IHC) staining. Opal Multiplex IHC staining was performed with appropriate positive and negative controls and imaged using a standard fluorescent microscope fitted with a spectral scanning camera(Mantra) in conjunction with Mantra snap software. Images were unmixed and annotated in in Form 2.2.0. Statistical analysis was performed using Graphpad Prism Version 7 and Stata Version 15.RESULTS Seventy-two patients with known MSI and BRAF status were included in the study. All patients were assessed for MSI by IHC and high resolution capillary electrophoresis testing and 44 of these patients successfully underwent quantitative multiplex IHC staining. Overall, there was a statistically significant increase in CD8+ T_(RM) cells in the MSI(BRAF mutant and wild type) group over the microsatellite stable(MSS) group. There was a statistically significant difference in CD8+ T_(RM) between high level MSI(MSI-H):BRAF mutant [22.57, 95% confidence interval(CI): 14.31-30.84] vs MSS [8.031(95%CI: 4.698-11.36)], P = 0.0076 and MSI-H:BRAF wild type [16.18(95%CI: 10.44-21.93)] vs MSS [8.031(95%CI: 4.698-11.36)], P = 0.0279. There was no statistically significant difference in CD8 T cells(both CD8+CD103-and CD8+CD103+T_(RM)) between MSI-H: BRAF mutant and wild type CRC.CONCLUSION This study has shown that CD8+ T_(RM) are found in greater abundance in MSI-H CRC, both BRAF mutant and MSI-H:BRAF wild type, when compared with their MSS counterpart. CD8+ T_(RM) may play a role in the immunogenicity in MSI-H CRC(BRAF mutant and BRAF wild type). Further studies should focus on the potential immunogenic qualities of T_(RM) cells and investigate potential immunotherapeutic approaches to improve treatment and survival associated with CRC.

Characterisation of colonic dysplasia-like epithelial atypia in murine colitis

AIM To determine if exacerbation of pre-existing chronic colitis in Winnie(Muc2 mutant) mice induces colonic dysplasia.METHODS Winnie mice and C57BL6 as a genotype control, were administered 1% w/v dextran sulphate sodium(DSS) orally, followed by drinking water alone in weeklong cycles for a total of three cycles. After the third cycle, mice were killed and colonic tissue collected for histological and immunohistochemical evaluation. Inflammation and severity of dysplasia in the colonic mucosa were assessed in H&E sections of the colon. Epithelial cell proliferation was assessed using Ki67 and aberrant β-catenin signalling assessed with enzyme-based immunohistochemistry. Extracted RNA from colonic segments was used for the analysis of gene expression using real-time quantitative PCR. Finally, the distribution of Cxcl5 was visualised using immunohistochemistry.RESULTS Compared to controls, Winnie mice exposed to three cycles of DSS displayed inflammation mostly confined to the distal-mid colon with extensive mucosal hyperplasia and regenerative atypia resembling epithelial dysplasia. Dysplasia-like changes were observed in 100% of Winnie mice exposed to DSS, with 55% of these animals displaying changes similar to high-grade dysplasia, whereas high-grade changes were absent in wild-type mice. Occasional penetration of the muscularis mucosae by atypical crypts was observed in 27% of Winnie mice after DSS. Atypical crypts however displayed no evidence of oncogenic nuclear β-catenin accumulation, regardless of histological severity. Expression of Cav1, Trp53 was differentially regulated in the distal colon of Winnie relative to wild-type mice. Expression of Myc and Ccl5 was increased by DSS treatment in Winnie only. Furthermore, increased Ccl5 expression correlated with increased complexity in abnormal crypts. While no overall difference in Cxcl5 mucosal expression was observed between treatment groups, epithelial Cxcl5 protein appeared to be diminished in the atypical epithelium. CONCLUSION Alterations to the expression of Cav1, Ccl5, Myc and Trp53 in the chronically inflamed Winnie colon may influence the transition to dysplasia.