Purpose: The significance of periodic tryptophan protein 1 (PWP1) expression in human cancer and its molecular mechanism of action have not been reported so far.
Materials and Methods: Immunohistochemistry was performed to analyze the expression of PWP1 in non-small cell lung cancer (NSCLC) tissues and statistical analysis was applied to analyze the relationship between PWP1 expression and the clinicopathological factors. The effects of PWP1 on NSCLC proliferation and invasion were determined by colony formation, transwell and MTT assays. Western blot analysis (WB), dual-luciferase reporter gene assays and immunofluorescence staining were performed to demonstrate whether PWP1 stimulates Wnt pathway and inhibits Hippo pathway. Co-immunoprecipitation (Co-ip) assays were used to confirm the potential role of PWP1 in Wnt and Hippo signaling pathways.
Results: PWP1 expression in NSCLC was higher than that in normal bronchial epithelium and normal submucosal glands. In addition, PWP1 expression had a positive correlation with poor differentiation, high pathological tumor-node-metastasis (TNM) stage, and lymph node metastasis. Kaplan–Meier database demonstrated that the overall survival time of patients with high PWP1 expression was significantly shorter than that of patients with low PWP1 expression. Mechanistically, we found that PWP1 could interact with DVL2 to upregulate β-catenin (thereby activating the Wnt pathway), whereas PWP1 could interact with Merlin (NF2) to downregulate p-MST1 (thereby inhibiting the Hippo signaling pathway). The effects of PWP1 on promoting the Wnt pathway or inhibiting the Hippo pathway were offset in DVL2- or Merlin-knockdown cells transiently overexpressing PWP1.
Conclusion: PWP1 expression in NSCLC was correlated with poor prognosis. PWP1 enhanced the activity of the Wnt pathway by interacting with DVL2, whereas PWP1 inhibited the activity of the Hippo pathway by interacting with Merlin. Together, these two effects promoted the detrimental biological behaviors of NSCLC cells.
Keywords: PWP1, Hippo, Wnt, DVL2, Merlin