Bioinformatics Analysis Reveals Microrchidia Family Genes as the Prognostic and Therapeutic Markers for Colorectal Cancer.

Aim: The aim of this study is to examine the role of the microrchidia (MORC) family, a group of chromatin remodeling proteins, as the therapeutic and prognostic markers for colorectal cancer (CRC).

Background: MORC protein family genes are a highly conserved nucleoprotein superfamily whose members share a common domain but have distinct biological functions. Previous studies have analyzed the roles of MORCs as epigenetic regulators and chromatin remodulators; however, the involvement of MORCs in the development and pathogenesis of CRC was less examined.

Objective: The current work examined the role of the MORCs as the therapeutic and prognostic markers for CRC.

Methods: The expressions and prognostic significance of MORC family genes in CRC were explored. The role of these genes in tumor immunity was comprehensively analyzed in terms of their functions in immune cell infiltration, tumor microenvironment (TME), and their interaction with immune regulatory genes such as immunosuppressive genes, immune checkpoints and immunostimulatory genes. The relations between MORC family genes, tumor mutation burden (TMB), DNA, mismatch repair (MMR), RNA methylation, microsatellite instability (MSI), and drug sensitivity were investigated using the R statistical software. The expressions of MORC4 in 150 CRC tissues and 60 paracancer tissues were detected by immunohistochemical method. CRC cell proliferation, migration, and invasion were measured by cell counting kit-8 (CCK-8), scratch assay, and transwell cell invasion assay.

Results: The expressions of MORC2 and MORC4 were significantly upregulated, whereas those of MORC1 and MORC3 were noticeably downregulated in CRC in comparison to their expressions in normal colorectal mucosal tissues. Patients with high-expressed MORC2 showed a more unfavorable prognosis than those with a low MORC2 level. Functional annotation analysis identified 100 MORC family genes with the most significant negative or positive correlations to diabetic cardiomyopathy, amyotrophic lateral sclerosis, oxidative phosphorylation, Huntington's disease, thermogenesis, Parkinson's disease, olfactory transduction, Alzheimer's disease, prion disease. MORC3 expression was positively correlated with Stromal score, Immune score and ESTIMATE score, while MORC2 expression was negatively related to the three scores in CRC, these correlations were not statistically significant. Additionally, the MORC family genes were significantly positively correlated with tumor-infiltrating immune cells such as T helper cells and exhibited close relations to some immunosuppressive genes such as CXCR4 and PVR, immunostimulatory genes such as TGFBR1, KDR, and CD160 as well as some immune checkpoint genes. It was found that the expressions of some members of MORC family genes were positively correlated with DNA methylation, MSI, TMB, MMRs, and drug sensitivity in CRC and that the mRNA and protein levels of MORC4 were remarkably upregulated in CRC tissues than in adjacent normal tissues (P<0.05). In the MORC4 knockdown group, DLD-1 cell proliferation was more inhibited than in the negative control (NC) and siRNA groups (P<0.05). Furthermore, the migratory capacity of DLD-1 cells and the number of cells crossing the basement membrane in the MORC4 knockdown group were reduced compared to the NC and siRNA groups (all P<0.05).

Conclusion: The expressions of MORC family genes were significantly different in CRC samples, which was related to the immune cell infiltration and prognosis of CRC. Thus, the MORC family genes were considered as markers for indicating the clinical immunotherapy and prognostic outcome of CRC.