The third mechanism is remodeling the tumor immune microenvironment: engineered bacteria secrete a repertoire of signaling molecules, such as cytokines, chemokines, and metabolites, to finely tune the spatiotemporal dynamics of innate and adaptive immunity, markedly expand and activate effector subsets including CD8+ T cells and NK cells, and even biosynthesize checkpoint inhibitors in situ, thereby synergistically inducing solid tumor regression, inhibiting metastasis, and establishing durable immune memory [107, 248–250]. This evidence concerns the gene CD8A and neoplasm.