Palladin promotes cancer stem cell-like properties in lung cancer by activating Wnt/B-Catenin signaling

Background: Cancer stem cells (CSCs) are responsible for drug resistance, cancer relapse, and metastasis. Here, we report the first analysis of Palladin expression and its impacts on stem cell-like properties in lung cancer. Methods: Tissue microarrays were used to investigate Palladin expression and its association with prognosis. Immunofluorescence (IF), flow fluorescence assay, and Western blot were performed to detect Palladin expression in 6 NSCLC cell lines. Cell phenotypes and drug resistance were evaluated. Xenograft models were constructed to confirm the role of Palladin in vivo. Results: By using the tissue microarrays, Palladin was identified to be highly expressed in the cytoplasm, specifically in the cytomembrane of NSCLC, and its high expression is associated with poor prognosis. Palladin is widely expressed and enriched in the sphere cells. The in vitro and in vivo studies showed that Palladin promoted stem cell-like properties, including cell viability, invasion, migration, self-renewal abilities, taxol resistance, and tumorigenicity. Western blot revealed that Palladin promoted the accumulation of beta-catenin and activated Wnt/beta-catenin signaling. Tissue microarrays analysis further confirmed the positive correlation between Palladin and beta-catenin. Wnt/beta-catenin pathway inhibitor blocked the Palladin-induced enhancement of sphere-forming. Conclusions: Palladin might act as an oncogene by promoting CSCs-like properties and tumorigenicity of NSCLC cells via the Wnt/beta-catenin signaling pathway. Besides, Palladin was identified to have the potential as a cell surface marker for LCSCs identification. These findings provide a possible target for developing putative agents targeted to LCSCs.