ALDH1A1 and colorectal carcinoma: ALDH1 is abundant in tumor samples from patients with CRC (21, 84), which can be used as a particular marker for CSCs of colorectal cancer (85), mainly including ALDH1A1, ALDH1B1, and ALDH1A3, are associated with poor prognosis and resistance to chemotherapy in colorectal cancer (86–88).