ITGAE Defines CD8+ Tumor-Infiltrating Lymphocytes Predicting a better Prognostic Survival in Colorectal Cancer

BACKGROUND: Tumor-infiltrating lymphocytes (TIL) in colorectal tumor tissue are significantly correlated with a favorable prognosis, such as CD8+ lymphocytes, which are also called tumor-reactive lymphocytes. However, not all tumor-infiltrating T cells confer benefit to patients. Therefore, it is of substantial benefit to identify a biomarker to demarcate these tumor-reactive lymphocytes. METHODS: We investigated whether ITGAE could be used to discriminate reactive CD8+ lymphocytes in colorectal cancer (CRC). TCGA colorectal cancer data sets (n1 = 492, n2 = 386) and FUSCC set (n3 = 276) were used in this study. Further phenotyping of ITGAE+ cells and the mechanistic basis were investigated. FINDINGS: In the training and testing sets from TCGA, ITGAE expression, which is strongly correlated with cytotoxic T cell markers (CD8/CD3/PD1), independently predicted longer disease-free survival (DFS) and overall survival (OS). In line with this, the association between ITGAE+ lymphocytes and survival has been confirmed in the FUSCC cohort for validation (P = .026). ITGAE + cells in the series always co-stained with CD8 were preferentially located in the tumor. Interestingly, ITGAE+ lymphocytes tended to associate with the epithelial–mesenchymal transition (EMT) with decreased Snail and increased E-cadherin expression accompanied. Finally, gene set enrichment analysis showed that immune activation was significantly enriched in the high ITGAE+ TIL group, accompanied by enriched EMT-related pathways. INTERPRETATION: Because of the specified expression of tumor-reactive CD8+ T-cells, ITGAE may be a promising biomarker for the rapid identification of immune infiltration in CRC.