CD8A and neoplasm: TMAO induces pyroptosis of tumor cells by activating the endoplasmic reticulum stress kinase PERK, thus enhancing the antitumor immune effect of CD8+ T cells.196 When tumor cells metastasize to distant sites through the circulatory system, they are exposed to severe stress within the blood vessels, such as hemodynamic shear forces and attacks of the immune system.197 Remarkably, circulating tumor cells can carry bacteria, which promote cytoskeletal reorganization and enhance the tumor cells’ resistance to fluid shear stress in the bloodstream.