Biological Effect And Mechanism Of Par3 In Lung Adenocarcinoma

The vast majority of lung cancer cases can be categorized as non-small cell lung cancer(NSCLC),which includes,broadly,lung adenocarcinoma(LuAC),squamous cell carcinoma,and large cell carcinoma subtypes.Metastasis is the leading cause of LuAC treatment failure and mortality.Understanding the mechanisms of cancer metastasis is important for further development of novel therapeutic agents and for the treatment of metastatic NSCLC.Partitioning defective protein 3(Par3)can activate the Tiaml/Rac pathway to inhibit invasion and metastasis in many cancers;however,the role of Par3 in lung adenocarcinoma remains unknown.The objective was to observe Par3 expression in lung adenocarcinoma and analyze its correlation with clinicopathological features by real-time RT-PCR and immunohistochemical analysis;To assess the effect of the Par3 in LuAC,we used short hairpin RNAs(shRNAs)targeting Par3 in A549 and H1299 cells.Western blotting and immunofluorescence staining analyses were used to detect the changes in Par3 expression after infection.Next we study the biological function by in vivo and in vitro experiments which include MTT assay,colony formation assay,scratch wound migration assays,Transwell invasion assay,hanging-drop assay,endothelial tube formation assay and tumor xenograft model.To study possible molecular mechanism of Par3 in lung adenocarcinoma.we also used shRNAs targeting 14-3-3? in A549 and H1299 cells,and to detect the changs of Tiaml-Racl pathway,Jak-Stat3 pathway and the interaction between Tiaml and 14-3-3? by many assays including PAK PBD pulldown assay,Racl G15A pulldown assay,Western blot and in and immunoprecipitation assay.Here we show that Par3 is downregulated in lung adenocarcinoma tissues and is associated with higher rates of lymph node metastasis and recurrence.Our functional study demonstrated that knock-down of Par3 promoted cell growth,cell migration,tumor formation,and metastasis in nude mice,all of which were effectively inhibited when 14-3-3? was silenced with short hairpin RNA(shRNA).We found that Par3 interacted with 14-3-3? protein and also showed that Par3 abrogated the binding of 14-3-3? to Tiaml,which was responsible for Racl activation.Knock-down of 14-3-3? inhibited Tiaml/Rac-GTP activation and blocked the invasive behavior of cells lacking Par3.These data suggest that loss of Par3 promotes metastatic behavior in lung adenocarcinoma cells through 14-3-3? protein.These findings provide a theoretical foundation for understanding the molecular mechanism of lung adenocarcinoma and developing novel Par3 based lung adenocarcinoma therapeutics.