The expression of P-glycoprotein in leukemia cells is associated with the upregulated expression of nestin, a class 6 filament protein

Abstract

Multidrug resistance (MDR) is a serious obstacle to the effective chemotherapeutic treatment of leukemia. Expression of plasma membrane P-glycoprotein (P-gp), a transporter involved in drug efflux, is the most frequently observed molecular causality of MDR. We observed the coexpression of P-gp and the filament protein nestin in the acute myeloid leukemia (AML) cell lines SKM-1 and MOLM-13 following the induction of P-gp expression using vincristine. Nestin is considered a marker of neural stem cells and neural progenitor cells. The aim of this study was to determine whether there is causal relationship between the expression of P-glycoprotein and the expression of nestin in both of these AML cell lines. The expression of P-gp was induced in SKM-1 cells by selective pressure using vincristine (VCR), mitoxantrone (MTX), azacytidine (AzaC) and lenalidomide (LEN). Whereas the selective pressure of VCR, MTX and AzaC also induced P-gp expression in MOLM-13 cells, LEN was found to be ineffective in this regard. In all cases in which P-gp expression was induced in SKM-1 and MOLM-13 cells, its expression was associated with the induction of nestin mRNA expression and the presence of a 200–220kDa nestin-immunoreactive protein band in western blots. Silencing P-gp expression using s10418 siRNA (known as the P-gp silencer) was associated with the downregulation of the nestin transcript level, demonstrated using RT-PCR. Nestin mRNA was also observed in two P-gp-positive variants of L1210 cells that were obtained either by selection with VCR or by transfection with a retrovirus encoding human P-gp. Detectable levels of nestin transcripts were not observed in P-gp-negative parental L1210 cells. Taken together, these results indicated that the induction of P-gp expression is causally associated with the expression of nestin in leukemia cells.