Suppressive effect of crepidatin on stemness of lung cancer cells

Abstract

Cancer stem cells (CSCs) have been perceived as rare populations driving cancer progression, metastasis, and drug resistance in leading cancers. The discovery of new compounds that attenuates CSCs’ properties is crucial for enabling advances in novel therapeutics to limit recurrence. We have reported the CSC-suppressing activity of chrysotoxine and crepidatin, two bibenzyl compounds isolated from Dendrobium pulchellum. Both chrysotoxine and crepidatin displayed suppression in CSC-like phenotypes, as determined in CSC-rich populations and primary CSCs in 3D culture and extreme limiting dilution assay. Individual treatment of chrysotoxine and crepidatin also affected the expression of CSC markers and associated proteins concomitantly decreased known CSCs markers. Importantly, chrysotoxine was shown to suppress active Src/Akt signal and intern depleted Sox2-mediated CSC. Our findings indicate a novel CSC-targeted role of chrysotoxine and its regulation by Src/Akt and Sox2, which may be exploited for the cancer treatment. At the same time, crepidatin showed the highest potency to kill human lung cancer cells. Crepidatin was accomplished as a drug targeting model for lung cancer stem cells. Crepidatin also suppressed CSC-like phenotypes, as determined by CSC-rich populations in 3D culture, clonogenic assay and extreme limiting dilution assay, when compared to cisplatin. The treatment of crepidatin showed dramatic suppression in the CSCs in lung cancer cells, as verified by several CSC phenotype assessments and CSC markers. In addition, crepidatin also suppressed epithelial to mesenchymal transition (EMT) markers and inhibited migratory behavior of CSCs. Importantly, we confirmed the CSC-targeted activity of crepidatin in CSC-rich primary lung cancer cells. The compound dramatically inhibited the formation of tumor spheres of primary lung cancer cells. Finally, we confirmed the effect of crepidatin on the aggressive stem‐like and invasive phenotype in lung cancer cells, where in vivo growth and aggressiveness of crepidatin and cisplatin treated cells were analyzed using the chorioallantoic membrane (CAM) assay. The results revealed that crepidatin significantly reduced tumor growth in lung cancer cells, when compared to nontreated cells, whereas the tumor sizes have been significantly increased in cisplatin treatment. These findings document a novel pharmacological action and establishes the underlying mechanism of chrysotoxine and crepidatin in negatively regulating CSC-like phenotypes and sensitizing resistant cancer cells. Therefore, the findings from this study would provide important insights that facilitate the further investigation and development of the two natural compounds, chrysotoxine and crepidatin, for CSC-targeted approaches.