Soluplus(®) micelles as a potential drug delivery system for reversal of resistant tumor

Inhibiting or circumventing drug resistance by using drug delivery systems (DDSs) such as micelles has attracted significant attention recently. In this present study, a polyvinyl caprolactam-polyvinyl acetate-polyethylene (Soluplus(®)) micelle was developed as the delivery system for doxorubicin (DOX) and evaluated both in vitro and in vivo. In vitro, Soluplus(®) micelles could significantly enhance the cellular accumulation of DOX in MCF-7/DOX cells, meanwhile, P-glycoprotein (P-gp)-mediated drug efflux was inhibited which was also verified in the membrane fluidity study. And MCF-7/DOX cells were found to be more susceptible to the cytotoxic effects of DOX-M. In vivo, both the P-gp inhibitors verapamil and Soluplus(®) could improve the cytotoxicity of DOX·HCl in MCF-7/DOX tumor-bearing mice, which were further certified by the effect of Soluplus(®) on P-gp inhibition. Furthermore, the excellent antitumor efficacy of DOX-M by intravenous injection was also observed, which indicated that the P-gp inhibition effect of Soluplus(®) could enhance the susceptibility of resistant tumor to DOX in vivo. In conclusion, our study suggested that Soluplus(®) micelles might be an applicable drug delivery system for enhancing the antitumor efficacy of P-gp substrates.