The combination therapy of salinomycin and gefitinib using poly(d,l-lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles for targeting both lung cancer stem cells and cancer cells

Purpose Lung cancer (LC) is the leading cause of cancer death worldwide. Evidences suggest that both LC cancer stem cells (CSCs) and cancer cells are supposed to be eliminated to achieve superior treatment effect against LC. Salinomycin could eradiate CSCs in various types of cancers, and gefitinib is a first-line therapy in LC. The purpose of the present study was to develop salinomycin-loaded nanoparticles (salinomycin-NPs) combined with gefitinib-loaded nanoparticles (gefitinib-NPs) to eradicate both LC CSCs and cancer cells. Methods Salinomycin and gefitinib were encapsulated separately by poly(d,l-lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles by the emulsion/solvent evaporation approach. The anti-LC activity of salinomycin-NPs and gefitinib-NPs was investigated. Results Salinomycin-NPs and gefitinib-NPs are of ~140 nm in size, high drug encapsulation efficacy and sustained release of drugs. CD133+ LC CSCs showed the characteristics of CSCs, including significantly enhanced stem cell gene expression, tumorsphere formation ability, and tumorigenicity in mice. Both salinomycin and salinomycin-NPs are capable of selectively inhibiting LC CSCs, as reflected by their enhanced cytotoxic effects toward CD133+ LC CSCs and ability to reduce tumorsphere formation in LC cell lines, whereas gefitinib and gefitinib-NPs could significantly inhibit LC cells. Salinomycin-NPs and salinomycin could reduce the population of LC CSCs in the tumors in vivo. It is noteworthy that salinomycin-NPs combined with gefitinib-NPs inhibited the growth of tumors more efficiently compared with salinomycin combined with gefitinib or single salinomycin-NPs or gefitinib-NPs. Conclusion Salinomycin-NPs combined with gefitinib-NPs represent a potential approach for LC by inhibiting both LC CSCs and cancer cells.