Real-time polymerase chain reaction (qRT-PCR) analysis The mRNA expression levels of the ABCB1 (Hs01069047), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH; Hs00985689) genes were measured using the TaqMan® gene expression assay (Applied Biosystems, Foster City, CA, USA). The GAPDH gene was used as an endogenous control, and each sample was analyzed in triplicate. The relative expression levels were calculated using the 2-ΔΔCtmethod with bone marrow as a calibrator. The high and low expression cut-off points were determined by the mean values observed in healthy donors.