CYP3A4 and leukemia: In this study we determined whether vitamin D sufficient vs. deficient mice differ in (a) intestinal expression of VDR target genes, such as Cyp3a, or (b) systemic exposure to the orally administered Cyp3a metabolized leukemia therapies dexamethasone and dasatinib, or (c) dexamethasone’s anti-leukemic efficacy.