Through the detail mechanism by which HDAC1 promoting drug resistance of AML remains unclear, we found that in HL-60/ADM cells, K562/A02 cells and primary BMCs of refractory AML, HDAC1 downregulating Apoptotic protease activating factor 1 (Apaf-1), a putative tumor suppressor gene that has been reported to closely correlated with drug resistance in lymphoma [37, 38] and as well as in AML [39], through directly combined with its promoter (Additional file 3: Figure S3). The gene discussed is APAF1; the disease is lymphoma.