Scientists have also cultured hPSCs in vitro to perfectly modify four colorectal cancer mutation genes including APC, P53, KRAS, and SMAD4 and then screened the mutant cells to construct the human colorectal cancer model to explore the specific mechanism of the intestinal stem cell of colon cancer (Drost et al., 2015). The gene discussed is SMAD4; the disease is colorectal cancer.