Wnt blockers inhibit the proliferation of lung cancer stem cells

Xueyan Zhang,1* Yuqing Lou,1* Xiaoxuan Zheng,1 Huimin Wang,1 Jiayuan Sun,1 Qianggang Dong,2 Baohui Han1 1Department of Pulmonary Medicine, Shanghai Chest Hospital, Shanghai Jiaotong University, Shanghai, People’s Republic of China; 2Section of Cancer Stem Cells, Shanghai Cancer Institute, Shanghai Jiaotong University, Shanghai, People’s Republic of China *These authors contributed equally to this work Background: Previous study has confirmed that the occurrence of Wnt pathway activation is associated with risk of non-small-cell lung cancer recurrence. However, whether the pharmacologic blocking of the Wnt signaling pathway could provide therapeutic possibility remains unknown. The aim of the present study was to evaluate the therapeutic functions of the Wnt signaling pathway inhibitor pyrvinium pamoate (PP) on lung cancer stem cells (LCSCs) in vitro. Methods: Colony formation and sphere culture were performed to enrich LCSCs from three lung cancer cell lines: PC9, SPC-A1, and A549. After confirming stemness by immunofluorescence, PP was employed for cell viability assay by comparison with three other kinds of Wnt signaling inhibitor: salinomycin, ICG-001, and silibinin. The effect of PP on LCSCs was further verified by colony formation assay and gene expression analysis. Results: LCSCs were successfully generated by sphere culture from SPC-A1 and PC9 cells, but not A549 cells. Immunofluorescence assay showed that LCSCs could express pluripotent stem cell markers, including NANOG, Oct4, KLF5, and SOX2, and Wnt signaling pathway molecules ß-catenin and MYC. Half-maximal inhibitory concentrations of PP on SPC-A1, PC9, and A549 were 10 nM, 0.44 nM, and 0.21 nM, respectively, which are much lower than those of salinomycin, ICG-001, and silibinin. Moreover, significantly decreased colony formation and downregulation of pluripotent stem cell signaling pathway were observed in lung cancer cells after treatment with PP. Conclusion: Wnt signaling inhibitor PP can inhibit proliferation of LCSCs, and the Wnt signaling pathway could be considered a promising therapeutic or interventional target in lung adenocarcinoma. Keywords: pyrvinium pamoate, Wnt signaling pathway, sphere culture, colony formation