ΔNp63α promotes cigarette smoke-induced renal cancer stem cell activity via the Sonic Hedgehog signaling pathway

Abstract Background : Cigarette smoke (CS) has been generally recognized as a chief carcinogenic factor in kidney cancer. Previous studies have demonstrated the stimulative effect of smoking on renal cancer stem cells (RCSCs); however, the underlying molecular mechanisms remain unclear. The induction of cancer stem cells (CSCs)by CS represents an early event in tumor initiation. Renal cancer-related gene ΔNp63α is highly expressed in renal epithelial tissues and contributes to the RCSCs characteristics of tumors. In this study, we investigated the role of ΔNp63α on the activity of RCSCs induced by CS and the regulation on the Sonic Hedgehog (SHH) signaling pathway. Methods : Western blot and immunohistochemistry were performed to determine the expression levels of ΔNp63α and RCSCs markers in renal cell carcinoma tissues. CCK-8 assay was used to detect the activity of RCSCs in different concentrations of cigarette smoke extract (CSE). Tumor sphere formation assay, Western blot, RT-PCR, and co-immunoprecipitation (Co-IP) were utilized to analyze the effect of ΔNp63α on the activity of RCSCs induced by CS and the activation of the SHH signaling pathway. Furthermore, the effects of tumor sphere formation and CS on the expression levels of ΔNp63α and RCSCs markers were examined in vivo by nude mouse tumor formation assay. Results : In renal cancer tissues, ΔNp63α and RCSCs markers in smokers expressed higher than that in non-smokers. RCSCs were effectively enriched by tumor sphere formation assay in vitro and in vivo . Besides, CS increased the expression of RCSCs markers and the capability of sphere-forming in vitro and in vivo. Furthermore, CS activated the Sonic Hedgehog (SHH) signaling pathway, and the specialized inhibitor alleviated the promotion of CS on RCSCs. ΔNp63α activates SHH signaling pathway and promotes CS-induced enhancement of RCSCs activity. Conclusions : ΔNp63α positively regulates the activity of CS-induced RCSCs via SHH signaling pathway.