IL8 derived from macrophages inhibits CD8 T-cell function by downregulating TIM3 expression through IL8-CXCR2 axis in patients with advanced colorectal cancer.

Background: T cell immunoglobulin and mucin domain-containing protein 3 (TIM3) is a vital immune checkpoint that regulates the immune response. However, the specific role of TIM3 in patients with colorectal cancer (CRC) have rarely been studied. In this study, we investigated the effect of TIM3 on CD8 T cells in CRC and explored the mechanism of TIM3 regulation in tumor microenvironment (TME).

Methods: Peripheral blood and tumor tissues of patients with CRC were collected to evaluate TIM3 expression using flow cytometry. Cytokines in the serum of healthy donors and patients with early- and advanced-stage CRC were screened using a multiplex assay. The effects of interleukin-8 (IL8) on TIM3 expression on CD8 T cells were analyzed using cell incubation experiments in vitro. The correlation between TIM3 or IL8 and prognosis was verified using bioinformatics analysis.

Results: TIM3 expression on CD8 T cells was obviously reduced in patients with advanced-stage CRC, whereas a lower TIM3 expression level was associated with poorer prognosis. Macrophage-derived IL8, which could inhibit TIM3 expression on CD8 T cells, was significantly increased in the serum of patients with advanced CRC. In addition, the function and proliferation of CD8 and TIM3CD8 T cells were inhibited by IL8, which was partly depending on TIM3 expression. The inhibitory effects of IL8 were reversed by anti-IL8 and anti-CXCR2 antibodies.

Conclusions: In summary, macrophages-derived IL8 suppresses TIM3 expression on CD8 T cells through CXCR2. Targeting the IL8/CXCR2 axis may be an effective strategy for treating patients with advanced CRC.