SARI Inhibits Estradiol-induced Cell Proliferation Of Lung Adenocarcinoma By Down-regulating The Src-Akt-Erk Signal Pathways

ObjectiveLung cancer is the leading cancer all over the world in morbidity and mortality,unfortunately its carcinogenesis is indistinct.Several studies have shown the level of sexual hormone and its receptor relates to carcinogenesis,development and prognosis.In recent years the incidence of lung cancer is increasing dramatically in women,and has displayed gender differences in age of onset,clinical presentation and histology,suggesting that lung cancer may relates to sexual hormone and its signal pathways.SARI(Suppressor of AP-1,regulated by IFN), is a new tumor suppressor gene found in the past few years. It is known as suppressor of AP-1, while AP-1over-expresses in90%human cancer.When transfected SARI,it reveals the results of cell-growth inhibition and apoptosis. For90%of cancers are based on similar mechanism to survival and grow,so it’s believed SARI may be a new therapy target to many kinds of cancers.Our preliminary work delineates SARI inhibits the invasion and metastasis of lung adenocarcinoma by modulating EMT(epithelial-mesenchymal transition).However, its role and mechanism in modulating Estradiol-induced cell proliferation of lung adenocarcinoma is largely unknown,our study was to investigate the function of Tumor suppressor gene SARI in Estradiol-induced cell proliferation of lung adenocarcinoma and its underlying signal pathways.MethodsWe transfected pcDNA-SARI in A549cells to over-express SARI. MTT assay was used to detect cell proliferation. Western blotting was used to analyze the protein levels of Src,Erk2,Akt and pSrcy41,pAkts473,pErk.Results1. Successfully transfected pcDNA-SARI in A549cells to overexpress SARI.SARI is weakly express in lung adenocarcinoma cell A549,while when we transfected pcDNA-SARI in A549cells,comparing to The Group Control vector,we found SARI over-express successfully in Group pcDNA-SARI detected by Western blotting assay.2. MTT assay was used to detect cell proliferation.The proliferation rate of Group E2was (148±10)%, comparing to the Group Control vector,the proliferation rate was up-regulated48%(P<0.05).The proliferation rate of Group E2+pcDNA-SARI was (92±4)%,comparing to the Group E2,the proliferation rate was down-regulated56%(P<0.05) because of transfecting SARI.The proliferation rate of Group pcDNA-SARI was (68±6)%.The MTT assay reveals over-expression of SARI significantly inhibited cell proliferation induced by estradiol in A549cell lines, proliferation rate was decreased by56%(P<0.05).3. Western blotting was used to analyze the protein levels of Src.The express level of pSrcy416was up-regulated after treatment of E2,the relative express level was2.59±0.36,while the total level of Src kept unchanged. The express level of pSrcy416was relatively down-regulated in Group pcDNA-SARI after treatment of E2,the relative express level was0.88±0.22,while the total level of Src kept unchanged.The differences was statistically significant (P<0.05).This assay indicated the protein levels of pSrcy416decreased in SARI over-expression A549cells after estradiol treatment (P<0.05),while protein levels of Src kept unchanged.4. Western blotting was used to analyze the protein levels of Akt.The express level of pAkts473was up-regulated after E2treatment,the relative express level was2.77±0.48,while the total level of Akt kept unchanged. The express level of pAkts473was relatively down-regulated in Group pcDNA-SARI after E2treatment,the relative express level was0.86±0.21,while the total level of Akt kept unchanged.The differences was statistically significant(P<0.05).This assay indicated the protein levels of pAkts473decreased in SARI over-expression A549cells after estradiol treatment (P<0.05), while protein levels of Akt kept unchanged.5. Western blotting was used to analyze the protein levels of Erk.The express level of pErk was up-regulated after E2treatment,the relative express level was3.48±0.47,while the total level of Erk2kept unchanged. The express level of pErk was relatively down-regulated in Group pcDNA-SARI after E2treatment,the relative express level was0.91±0.09,while the total level of Erk2kept unchanged.The differences was statistically significant (P<0.05).This assay indicated the protein levels of pErk decreased in SARI over-expression A549cells after estradiol treatment (P<0.05), while protein levels of Erk2kept unchanged.These results suggest SARI inhibits Estradiol-induced cell proliferation of lung adenocarcinoma by down-regulating the Src-Akt-Erk signal pathways.Conclusions1. SARI is weakly express in lung adenocarcinoma cell A549,while when we transfected pcDNA-SARI in A549cells,we found SARI over-express successfully detected by Western blotting assay.2. Estradiol promotes the proliferation of lung adenocarcinoma,SARI not only inhibits cell proliferation of lung adenocarcinoma,but also inhibits Estradiol-induced cell proliferation of lung adenocarcinoma.3. The underlying mechanisms of estradiol-induced proliferation of lung adenocarcinoma may relate to activate the Src-Akt-Erk signal pathways.. The underlying mechanisms of SARI inhibiting Estradiol-induced cell proliferation of lung adenocarcinoma were likely to attenuating the Src-Akt-Erk signal pathways activated by estrogen.This study not only delineates the mechanisms estradiol-induced proliferation of lung adenocarcinoma,but also reveals functional role of SARI in inhibiting proliferation of lung adenocarcinoma. The delineation of SARI function could provide a potential intervention strategy for lung adenocarcinoma.