ABCB1 and leukemia: The decrease in MDR-1 expression and consequently an increase in cellular sensitivity to doxorubicin was observed after the increase of the cellular levels of miR-451 in a doxorubicin-resistant breast cancer cell line (MCF-7/DOX) [75], miR-331-5p in resistant K562/DOX leukemia cells [76], and miR-27a in a chronic myeloid leukemia cell line (K562) [76].