CD8A and neoplasm: 1. Tumor progression stage: Activates the Smad2/3-Snail pathway, induces epithelial-mesenchymal transition (EMT), and enhances the migration and invasion capabilities of tumor cells;2. Inhibits the cytotoxicity of CD8+ T cells, promotes the differentiation of regulatory T cells (Treg), and constructs an immunosuppressive microenvironment;3. Promotes tumor angiogenesis and distant metastasis processes such as bone metastasis