Reshaping tumor immune microenvironment by Epstein-Barr virus activation in the stroma of colorectal cancer

The formation of tumor immune microenvironment (TIM) is complicated and poorly understood. Little is known about the effect of a viral infection potentially inducing an additional immune response in the TIM. Here, we identify Epstein -Barr virus (EBV) expression in the TIM in colorectal cancer (CRC) tissue through EBV-encoded RNA in-situ hybridization and RNA sequencing data and investigate the effects of EBV on TIM composition and clinical outcomes. EBV was detected in tumor-infiltrating lymphocytes, but not in cancer cells. EBV positivity was associ-ated with older age, male sex, and SMAD4 mutations. EBV-positive tumors were characterized by enrichment in chemokine/cytokine signaling pathways and altered immune cell composition, including plasma and CD4 T cells, as well as can-cer cells intrinsically enriched pathways related to immune tolerance, leading to poor prognosis. In conclusion, we identified EBV expression in TIM and suggested its association with poor prognosis by altering the TIM in CRC.