Mechanism And Role Of SET Oncogene In Non-small Cell Lung Cancer

Background and Objective:SET oncoprotein is an endogenous inhibitor of protein phosphatase 2A(PP2A).SET-mediated PP2 A inhibition is an important regulatory mechanism for promoting cancer initiation and progression of various malignancies.However,its potential relevance in non-small cell lung cancer(NSCLC)remains mostly unknown.The aim of this study is to evaluate the molecular effects of SET deregulation and its potential clinical significance in NSCLC.Methods:1.We retrospectively analyzed data and samples collected from 248 radically resected NSCLC patients with pathological stage I-IIIA between June 2010 and June 2012 at the Tianjin Medical University Cancer Institute & Hospital.To further examine the expression of SET in archival primary NSCLC,we performed IHC analysis in 248 paraffin-embedded NSCLC as well as 155 adjacent normal lung tissues.Correlations between SET and survival parameters were analyzed and prognostic factors were identified.2.We examined SET expression in several human NSCLC lines and one normal human lung cell epithelial cell line BEAS-2B.Select A549,H1975,HCC827 and PC9 cells for subsequent tests.The four NSCLC lines were transtected with SET siRNA.Western blot was performed to detect SET expression after transfection,then the expression of AKT and ERK1/2 protein were also observed.MTT assay and colonosphere formation were used to evaluate cell proliferation.The migration and invasion assays were performed using the Transwell assay.Cell cycle was demonstrated by Flow Cytometry assay.3.MTT was used to estimate the IC50 of FTY720 and Erlotinib.A549,H1975,HCC827 and PC9 cells were treated with Erlotinib alone or in combination with FTY720.We next examined whether combining a SET antagonist,FTY720,sensitized NSCLC cells to Erlotinib.The cell proliferation and cell cycle were detected by MTT and Flow Cytometry assays.Western blot was performed to detect the expression of p-EGFR?p-STAT3?p-AKT?p-ERK1/2.Results:1.In this study,high SET expression was detected in 46.8% of ADs and SCCs,and was significantly correlated with age(?~2 = 8.936,P = 0.003),smoking index(?~2 = 3.879,P = 0.049),clinical stage(?~2 = 7.666,P = 0.022),lymph node metastasis(?~2 = 3.997,P = 0.046).By univariate analysis,clinical stage(P = 0.001,DFS;P = 0.008,OS),lymph node metastasis(P = 0.002,DFS;P = 0.021,OS),high SET expression(P = 0.008,DFS;P < 0.001,OS)were correlated with worse disease-free survival(DFS)and overall survival(OS).By multivariate analysis,high SET expression(HR = 2.025,95%CI:1.449-2.830,P < 0.001,OS;HR = 1.448,95%CI:1.027-2.041,P = 0.042,DFS)were independent unfavorable prognostic factor for DFS and OS.2.We found SET were overexpressed in a varity of NSCLC cells.Moreover,we investigated the oncogenic role of SET by SET-siRNA and showed that knockdown of SET in NSCLC cell lines resulted in attenuated proliferative and invasive abilities.The biological effect of SET on proliferation and invasion was mediated by the inhibition of the PP2 A,which in turn,activation of AKT and ERK1/2 signaling pathways,decreased the expression of p21.3.We found HCC827 and PC9 were sensitive to Erlotinib.Furthermore,the effect of Erlotinib on NSCLC cell growth could be enhanced by SET antagonist FTY720,blocking cell cycle to G1/S,G2/M phase,inhibition of EGFR/STAT3,PI3K/AKT and ERK1/2 signal pathway,upregulated the expression of P21 and P27 protein,and decreased the expression level of CyclinD1.Conclusion:Taken together,SET oncoprotein plays an important role in NSCLC progression,which could serve as a potential prognosis marker and a novel therapeutic target for NSCLC patients.FTY720 can elevate sensitivity to Erlotinib in NSCLC cell lines.Our novel combination offers a promising therapy in advanced NSCLC,for which there are currently few effective treatment options after the tumors have progressed during first-line anticancer treatments.