GFRA1 and colorectal carcinoma: All cell lines exhibited endogenous expression of GFRα1, GFRα3 and RET. To determine the functional effects of ARTN in CRC progression, Caco2, DLD1 and HCT116 cells were stably transfected with the pIRESneo3-ARTN construct (-ARTN) or with pIRESneo3 as the vehicle control (-Vec).