Wnt/β-catenin pathway regulates <it>ABCB1</it> transcription in chronic myeloid leukemia

<p>Abstract</p> <p>Background</p> <p>The advanced phases of chronic myeloid leukemia (CML) are known to be more resistant to therapy. This resistance has been associated with the overexpression of <it>ABCB1</it>, which gives rise to the multidrug resistance (MDR) phenomenon. MDR is characterized by resistance to nonrelated drugs, and P-glycoprotein (encoded by <it>ABCB1</it>) has been implicated as the major cause of its emergence. Wnt signaling has been demonstrated to be important in several aspects of CML. Recently, Wnt signaling was linked to <it>ABCB1</it> regulation through its canonical pathway, which is mediated by β-catenin, in other types of cancer. In this study, we investigated the involvement of the Wnt/β-catenin pathway in the regulation of <it>ABCB1</it> transcription in CML, as the basal promoter of <it>ABCB1</it> has several β-catenin binding sites. β-catenin is the mediator of canonical Wnt signaling, which is important for CML progression.</p> <p>Methods</p> <p>In this work we used the K562 cell line and its derived MDR-resistant cell line Lucena (K562/VCR) as CML study models. Real time PCR (RT-qPCR), electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), flow cytometry (FACS), western blot, immunofluorescence, RNA knockdown (siRNA) and Luciferase reporter approaches were used.</p> <p>Results</p> <p>β-catenin was present in the protein complex on the basal promoter of <it>ABCB1</it> in both cell lines <it>in vitro</it>, but its binding was more pronounced in the resistant cell line <it>in vivo</it>. Lucena cells also exhibited higher β-catenin levels compared to its parental cell line. <it>Wnt1</it> and <it>β-catenin</it> depletion and overexpression of nuclear β-catenin, together with TCF binding sites activation demonstrated that <it>ABCB1</it> is positively regulated by the canonical pathway of Wnt signaling.</p> <p>Conclusions</p> <p>These results suggest, for the first time, that the Wnt/β-catenin pathway regulates <it>ABCB1</it> in CML.</p