ABCB1 and acute promyelocytic leukemia: In line with earlier findings, subsequent study using semi-quantitative RT PCR demonstrated that ATRA can induce ABCB1 mRNA expression in several hematological malignancy cell lines, including human acute T-cell leukemia (H9), chronic myeloid leukemia in blast crisis (K562), AML (KG-1), and APL (NB4), as well as in their RARα-transfected derivatives (H9/RAR, K562/RAR, KG-1/RAR, and NB4/RAR), irrespective of the baseline transporter expression levels [76].