Function And Inner Mechanism Of PLEK2 In Oesophageal Squamous Cell Carcinoma

Oesophageal squamous cell carcinoma(ESCC)is a major pathology subtype of oesophageal cancer in China.Though the comprehensive therapy of ESCC has been proved gradually,the overall survival of ESCC patients is still unsatisfied.ESCC has a relatively unfavourable prognosis due to metastasis and chemoresistance.Therefore,it would be a breakthrough in improving the effect of the therapy and the prognosis of ESCC patitents to explore the inner mechanism of and the biomarkers of metasis and chemo-resisitance of ESCC.Our previous research established a comprehensive ESCC database(GSE53625),which has been uploaded on GEO database.In this study,TCGA and GSE53625 databases were used to establish the Plekstrin-2(PLEK2)expression profile and Overall survival(OS)rate.After analynazing the data we found that PLEK2 predicted poor prognosis in ESCC.Moreover,PLEK2 expression was also related to the overall survival of ESCC patients undergoing chemotherapy.All of the above results indicate the important role of PLEK2 in ESCC.To verify the conjecture,loss-of-function assays were performed to explore the effects of PLEK2 on the proliferation,migration and invasion of ESCC cells in vitro and in vivo.Upstream and downstream effectors of PLEK2 were identified by RNA sequencing,quantitative real-time PCR,Western blot,luciferase reporter,and chromatin immunoprecipitation assays were conducted to detecte the inner mechanism of metastasis regulated by PLEK2.Our results show that elevated PLEK2 expression in ESCC was closely related to poor OS.Repression of PLEK2 decreased the proliferation,migration and invasion of ESCC cells in vitro and decreased tumorigenicity and distant metastasis in vivo.On the other hand,elevated PLEK2 levels had the opposite effects on ESCC cells.What's more,elevated PLEK2 expression in ESCC was closely related to poor response to chemotherapy.Overpression of PLEK2 increased the chemoresistance of ESCC cells.PLEK2 expression in subcutaneous xenograft tumours was increased upon treatment with a higher dose of cisplatin.Mechanistically,by stimulating Smad2/3 complex,which can directly bind to the promoter sequences of PLEK2,tranforming growth factor-?(TGF-?)uprelated the expression of PLEK2 and thus promoted the metastasis of ESCC.Lipocalin 2(LCN2),a crucial regulatory molecule in metastasis of ESCC,was identified as the following molecules regulated by PLEK2.Overexpression of LCN2 in ESCC cells with PLEK2 stably knockdown reversed the effects of decreased ability of migration and invasion.In addition,TGF-? increased the expression of LCN2,but the effect disappeared when PLEK2 was knocked down in ESCC cells.Moreover,the Akt was phosphorylated in the whole regulatory processes mentioned above,indicating the involvement of Akt pathway.In conclusion,this study detected the major role of PLEK2 in driving metastasis and chemoresistance in ESCC by regulating LCN2,which activates the Akt pathway.Our findings indicate the potential use of PLEK2 as a biomarker to predict prognosis and as a therapeutic target for ESCC.