Cancer stem cells (CSCs) play a key role in non-small cell lung cancer (NSCLC) chemoresistance and metastasis. In this study, we used two NSCLC cell lines to investigate the regulating effect of hypoxia in the induction and maintenance of CSC traits. Our study demonstrated hypoxia-induced stemness and chemoresistance at levels comparable to those in typical CSC sphere culture. Activation of the NF-κB pathway (by transfection of NF-κB-p65) plays a key role in NSCLC CSCs and chemoresistance. Disulfiram (DS), an anti-alcoholism drug, showed a strong in vitro anti-CSC effect. It blocked cancer cell sphere reformation and clonogenicity, synergistically enhanced the cytotoxicity of four anti-NSCLC drugs (doxorubicin, gemcitabine, oxaliplatin and paclitaxel) and reversed hypoxia-induced resistance. The effect of DS on CSCs is copper-dependent. A very short half-life in the bloodstream is the major limitation for the translation of DS into a cancer treatment. Our team previously developed a poly lactic-co-glycolic acid (PLGA) nanoparticle encapsulated DS (DS-PLGA) with a long half-life in the bloodstream. Intra venous injection of DS-PLGA in combination with the oral application of copper gluconate has strong anticancer efficacy in a metastatic NSCLC mouse model. Further study may be able to translate DS-PLGA into cancer applications.

Background: Steric stabilization of liposomes using PEGylation has been used widely in pharmaceutical research to overcome the limitations of conventional liposomes and to extend circulation time. PEGylation tended to improve the physicochemical stability and reverse the chemoresistance in multidrug-resistant (MDR) breast cancer cell lines. In this study, PEGylated formulations of disulfiram (DS) and paclitaxel (PAC) were developed using the ethanol-based proliposome technology. Methods: PEGylated liposomal formulations of disulfiram (DS) and paclitaxel (PAC) were developed using the ethanol-based proliposome approach combined with high-pressure homogenization (HPH). The liposomes were characterized for particle size, polydispersity index (PDI), zeta potential, drug loading efficiency (DLE%), and drug entrapment efficiency (DEE%). Cytotoxicity studies were performed on sensitive (MCF7, MDA-MB-231) and chemoresistant (MDA-MB-231_PAC10) breast cancer cell lines using the MTT assay to assess the anti-ancer potential of the formulations. Synergistic cytotoxic effects of DS and PAC co-delivery were also evaluated. Results: There was no significant difference in drug loading (DLE%) and drug entrapment efficiency (EE%) between conventional liposomes and the developed PEGylated vesicles. DS demonstrated higher loading in liposomes than PAC, and a greater cytotoxic effect on both sensitive (MCF7 and MDA-MB-231) and chemoresistant (MDA-MB-231_PAC10) human breast cancer cell lines. For both DS- and PAC-loaded liposomes, PEGylation did not compromise the cytotoxic effect on both sensitive and chemoresistant cells. Interestingly, the combination of DS- and PAC-loaded PEGylated liposomes had significantly higher cytotoxic effect and lower IC50 than that of each drug alone. Conclusions: Overall, PEGylated liposomal formulation of DS and PAC acted synergistically to reverse the multidrug resistance in breast cancer cells and could serve as a promising system for delivery of PAC and DS simultaneously in one formulation using an alcohol-based proliposome formulation.