Selective targeting of FAK–Pyk2 axis by alpha-naphthoflavone abrogates doxorubicin resistance in breast cancer cells

• Defined a new role for ANF in abrogating Dox resistance in breast cancer cells.
• ANF decreases survival via inhibition of FAK–Pyk2 axis in Dox resistant cells.
• ANF increases Dox retention through inhibition of P-gp pumps Dox resistant cells.
• ANF has broad safety profile and inhibits growth of Dox-resistant cells in vivo.
• ANF is an attractive anti-cancer drug in patients presenting with Dox resistance.

Despite an initial positive response, breast cancer cells inevitably acquire resistance to doxorubicin (Dox). Alpha-naphthoflavone (ANF) is a well-known chemopreventive agent; however, its anti-cancer properties have not been established. We examined the therapeutic efficacy of ANF in doxorubicin-resistant MCF-7 (MCF-7/Dox) breast cancer cells and investigated its underlying molecular mechanisms of action. MCF-7/Dox cells expressed constitutively active forms of the tyrosine kinases: focal adhesion kinase (FAK-Y397) and protein tyrosine kinase 2 beta (Pyk2- Y579/580) compared with parental MCF-7 cells. ANF significantly enhanced the sensitivity of MCF-7/Dox cells to Dox cytotoxicity in vitro and when co-administered in vivo. This ANF-mediated chemosensitization has dual mechanisms of action: (a) intracellular Dox retention via suppression of P-glycoprotein pump activity, and (b) inhibition of clonogenic cell survival via de-phosphorylation of FAK, Pyk2, and EGF-induced Akt in MCF-7/Dox cells and tumor xenografts. Because of its strong chemosensitization action, broad safety profile, and health benefits, ANF is an attractive anti-cancer drug with therapeutic implications to circumvent drug resistance in breast cancer patients.