FOXN3 attenuates doxorubicin resistance of bladder urothelial carcinoma via SIRT6/PI3K/AKT/mTOR pathway

Abstract

Purpose: To investigate the effect of forkhead box N3 (FOXN3) protein on doxorubicin (DOX) resistance of urothelial carcinoma (BLCA). Methods: Bioinformatics prediction and immunoblotting were used to evaluate FOXN3 expression in BLCA tissues and cells. The FOXN3 overexpression was achieved by cell transfection. The effects of FOXN3 on DOX resistance and cell apoptosis were determined by immunoblotting, DOX resistance assay, and flow cytometry, while immunoblotting was applied to evaluate SIRT6/PI3K/AKT/mTOR signaling activity. Finally, SIRT6 overexpression and exogenous addition of a PI3K/AKT activator were used to investigate the molecular mechanism by which FOXN3 regulates DOX resistance phenotype. Results: The FOXN3 was downregulated in DOX-resistant BLCA tissues and cells while its overexpression attenuated doxorubicin resistance (p < 0.01). Furthermore, apoptotic cell ratio increased from 7.54 to 26.83 % in J82/DOX cells and from 6.31 to 17.89 % in T24/DOX cells (p < 0.01) after FOXN3 overexpression. Moreover, FOXN3 upregulation inhibited sirtuin 6 (SIRT6) expression and inactivated PI3K/AKT/mTOR signaling pathway. Both SIRT6 overexpression and PI3K/AKT activation abrogated the FOXN3-mediated inhibition of DOX resistance in BLCA cells. Conclusion: The FOXN3 attenuates the DOX resistance of BLCA through SIRT6/PI3K/AKT/mTOR pathway, thus providing a promising therapeutic strategy for the management of BLCA.