Wnt2 promotes non-small cell lung cancer progression by activating WNT/β-catenin pathway.

BACKGROUND Wnt2 is overexpressed and able to promote tumorigenesis in many types of cancer. However, its expression and role in lung cancer has not been well clarified yet. In this study, we aims to investigate the expression pattern, clinical significance and the underlying molecular mechanism of Wnt2 in non-small lung cancer (NSCLC). METHODS Immunohistochemical staining and ELISA assays were applied to detect Wnt2 level in tumor tissue and serum. EDU incorporation assays and colony formation assays were used to evaluate the growth-promoting effect of Wnt2 in vitro. Then we performed western blot and immunofluorescence assays to detect the activation of WNT signaling pathway. Finally mice engrafted with NSCLC tumor cells were used to assess the role of Wnt2 in vivo. RESULTS Immunohistochemical staining consisting of 264 NSCLC tumor tissues showed that a high level of Wnt2 was associated with a poor overall survival (OS) and relapse-free survival (RFS) of NSCLC patients (P = 0.002 and 0.0005, respectively). Multivariate analysis presented that Wnt2 level in tumor tissue was an independent prognostic factor (P = 0.049 for OS and P = 0.002 for RFS, respectively). Furthermore, ELISA assays for 181 individuals (116 NSCLC and 65 controls) revealed that serum Wnt2 levels in adenocarcinoma was significantly higher than that in healthy volunteers (P < 0.0001). In vitro H460 cell line stably overexpressing Wnt2 showed enhanced growth activity than the control cells whereas knockdown of Wnt2 by siRNA in H1299 cells resulted in decreased growth activity. Additionally, Wnt2 level in tumor tissues was significantly associated with Ki-67 level (rs: 0.316; P < 0.0001). Immunofluorescence and Western blot assays detected the translocation of β-catenin from cytoplasm into nucleus, which indicated that Wnt2 probably promotes proliferation by activating WNT/β-catenin pathway. In vivo H460 cells expressing exogenous Wnt2 showed increased growth-promoting effect in Balb/c nude mice than control cells. CONCLUSIONS The present study for the first time suggested that Wnt2 was both a prognostic and a diagnostic biomarker for NSCLC. Tumor-derived Wnt2 can promote growth activity of NSCLC cells through activating WNT/β-catenin signaling pathway.