For example, Wang et al. found that All-trans retinoic acid (ATRA) down-regulated Chk1 in FLT3-ITD AML cells, and the combination of ATRA and DNA damage drug SN38 significantly improved the anti-tumor effect of either ATRA or SN38 when used alone25. The gene discussed is CHEK1; the disease is acute myeloid leukemia.