ALDH1A1 and colorectal carcinoma: HOXA4 and HOXA9 knockdown also changed the expression of SC markers, such as ALDH1, ALCAM, (CD166) and LGR5. Treatment of CRC cells with the differentiating agent all-trans-retinoic acid (ATRA) decreased HOXA4, HOXA9, and HOXD10 expression in parallel with decreases in SC levels.