AQP9 weakens the cytotoxicity of CD8+ T cells in colon adenocarcinoma by boosting M2 polarization of macrophages under hypoxia conditions.

Background: Colon adenocarcinoma (COAD) is a leading cause of cancer mortality, with Aquaporin 9 (AQP9) implicated in its progression. M2 macrophages in the tumor microenvironment (TME) promote cancer metastasis, but the role of AQP9 on M2 macrophages remains unelucidated.

Research design and methods: Using COAD cell lines, AQP9 expression was analyzed via RT-qPCR and Western blot (WB). Hypoxic conditions were simulated to assess HIF-1α and AQP9 interactions through ChIP and dual-luciferase assays. AQP9 knockdown effects on proliferation/migration were tested via colony formation and wound healing. M2 macrophage polarization and CD8+ T cell cytotoxicity were evaluated using flow cytometry, ELISA, and IHC in co-culture systems.

Results: AQP9 was upregulated in COAD and correlated with poor prognosis. After AQP9 in COAD cells was knocked down, the abilities of tumor cells to migrate and proliferate were dampened. Hypoxia upregulated HIF-1α, which transcriptionally activated AQP9. Knocking down AQP9 repressed the M2 polarization of macrophages, thereby reinforcing the cytotoxicity of CD8⁺ T cells. No adverse events were reported in vitro.

Conclusion: AQP9 promotes COAD progression by driving HIF-1α-mediated M2 polarization, impairing CD8+ T cell function. Key limitations include the lack of in vivo validation and clinical cohort analysis.