CEACAM5 and colorectal carcinoma: FvcA, a type Vc trimeric autotransporter adhesin, also known as CbpF, binds both carcinoembryonic antigen (CEA), a tumor protein associated with many cancers, including CRC, and CEACAM1 (95), a type 1 membrane receptor protein that is highly expressed in the tumor microenvironment, where it functions in tolerance and exhaustion (96).