CHEK1 and acute myeloid leukemia: Consistent with the above findings, panobinostat decreases the expression of BRCA1, CHK1, and RAD51, potently enhanced DNA DSBs and apoptosis, and abrogated S and/or G2/M checkpoints induced by cytarabine or DNR in 3 out of the four AML cell lines (THP-1, U937, and OCI-AML3, Figures 2 and S2A, C, and E).