Fig. 7

Increased expression of CD8 and CXCR3 and low IL-17A levels in the tumor stroma predicts better survival for CRC patients. a The expression levels of Th17 and CXCR3⁺CD8⁺ T cells in tumor tissues from early- and advanced-stage CRC patients were analyzed by flow cytometry. b Correlation between the concentration of the percentage of Th17 cells in CD4⁺T cells and CXCR3⁺CD8⁺ T cells in CD8⁺ T cells. Data were analyzed by Spearman’s rank correlation. c Expression of CD8, CXCR3, and IL-17A was measured in consecutive tumor sections of two patients by immunohistochemistry. d OS analysis of CRC patients with high and low IL-17A and CXCR3 expression (n = 70) presented as a Kaplan-Meier curve. High, IRS > 4; low, IRS ≤ 4. e OS of CRC patients with differential expression of CXCR3, CD8, and IL-17A. H, high, IRS > 4; L, low, IRS ≤ 4. f Diagram of the proposed mechanism. In the CRC circulation, Th17 cell-derived IL-17A activates the STAT3 pathway in CD8⁺ T cells, resulting in decreased CXCR3 expression and inhibiting migration of CD8⁺ T cells toward the CXCL10 secreted by tumor cells in tumor tissues. Targeting the STAT3 pathway leads to infiltration of CD8⁺ T cells into tumor tissues, eventually attenuating tumor progression