GPR4 and colorectal cancer: On one hand, GPR4-knock out (KO) mice showed reduced tumorigenesis after the orthotropic transplantation of cells from murine breast (4T1) or colon cancer (CT26) cell lines [156] while suppression of GPR4 in human colorectal cancer (HCT116) cells significantly attenuated tumor growth of subcutaneous xenografts and reduced liver invasion in a metastasis model in nude mice [153].