CD8A and neoplasm: However, tumor cells produce immunosuppressive metabolites in the TME, leading to poor activation and impaired function of CD8+T cells.12 These metabolites, such as lactate, kynurenine, cholesterol, succinate, and D-2-hydroxyglutarate (D-2HG), accumulate within the TME and impair the ability of CD8+T cells,13–17 leading to immune exhaustion and dysfunction.