USP32 Promotes Cancer Cell Invasion, Macrophage M2 Polarization, and CD8+ T Cell Apoptosis in Gastric Cancer Through Upregulation of DAPK1.

M2-like macrophages and CD8+T cells are key immune components that influence tumor behavior and treatment response. Ubiquitin-specific protease 32 (USP32) is established as a key oncogenic factor in gastric cancer (GC). This study aimed to investigate the role of USP32 in regulating M2 macrophage polarization and CD8+T cell dysfunction in GC. Macrophages derived from THP1 cells (THP1-M0) or CD8+T cells were co-cultured with transfected AGS and HGC-27 GC cells. The proportion of CD206 M2 macrophages and the apoptosis of CD8+T cells were assessed by flow cytometry. Cell invasion was analyzed by transwell assay. The interaction between USP32 and death-associated protein kinase 1 (DAPK1) was verified by GST pull down and Co-immunoprecipitation (Co-IP) experiments. The effect on tumor growth was tested by subcutaneous xenograft studies. USP32 and DAPK1 were overexpressed in GC tissues and cell lines. Mechanistically, USP32 stabilized DAPK1 protein through deubiquitination. DAPK1 downregulation reversed USP32-mediated enhancement in GC cell invasion, macrophage M2 polarization, and CD8+T cell apoptosis in vitro. USP32 depletion exhibited an in vivo anti-growth effect on AGS subcutaneous xenografts. This study identifies the USP32/DAPK1 cascade as a crucial regulator of M2 macrophage polarization and CD8+T cell apoptosis in GC, providing a novel mechanistic link between post-translational regulation and tumor immune evasion.