CEACAM5 and colorectal cancer: To evaluate CEA‐dependent CAR‐HMs activation, colorectal cancer cell lines (MC38CEA and CT26CEA) that stably express high levels of CEA were generated following published protocols (Figure S3, Supporting Information).[36] CARs were stably integrated into CAR‐HMs and CAR‐mediated downstream signaling pathways were significantly activated upon exposure to MC38CEA and CT26CEA cells (Figure2a,b; Figure S4a, Supporting Information).