SMAD4 and colorectal carcinoma: However, loss in the TGF-β receptor or SMAD4 commonly occurs in sporadic CRC patients and cell lines, such as SW480, HT-29, SW620 (absent SMAD4 protein and allelic loss at SMAD4), CaCO2 (SMAD4 point mutations and rapid SMAD4 protein degradation), and HCT-116 (mutation in TGFBIIR) [46].