Etoposide is another agent used in many induction regimens.21, 22 All three of these agents are substrates for CYP3A4,23, 24 and cytarabine is also inactivated by cytidine deaminase (CDA).25, 26 Chemotherapeutics can induce CYP3A4 activity in human liver cells.28 Thus, the clinical status of the AML and its treatment could theoretically influence the expression of CYP3A4 and CDA in the BM microenvironment, and hence impact associated drug resistance. Here, CDA is linked to acute myeloid leukemia.