Reversal of Imatinib resistance in BCR-ABL-positive leukemia after inhibition of the Na+/H+ exchanger.

The present study was undertaken to estimate the therapeutic benefit to down-regulate the Na(+)/H(+) exchanger 1 (NHE1) for reversing chemoresistance of BCR-ABL-positive leukemia patient cells and cell lines. As a result, after treatment with specific NHE1 inhibitor Cariporide or high K(+) buffer to decrease intracellular pH (pH(i)), cells from relapsed patients exhibited decreased Pgp level, enhanced Rhodamine123 and drug accumulation, decreased colony-forming ability and the modulations of mitogen-activated protein kinases (MAPKs) activities. Furthermore, we used BCR-ABL-positive cell line K562 and its resistant counterparts K562/DOX and K562/G01 cell lines for further study. Together, these findings suggest that Pgp may be associated with the reversal of drug resistance in BCR-ABL-positive leukemia patients and cell lines by the inhibition of NHE1 though MAPK pathways.