氨基酸转运载体2 (ASCT2)对胃癌细胞增殖的影响及其潜在机制

Effect of amino-acid transporter 2 (ASCT2) on gastric cancer cell growth and its potential mechanism

目的研究氨基酸转运载体2 (amino-acid transporter 2,ASCT2)对胃癌发生发展的影响及其潜在调控分子机制。方法使用瞬时过表达上调ASCT2,短发夹RNA (short hairpin RNA,shRNA)干扰技术下调ASCT2。Western blot法检测过表达或干扰ASCT2后蛋白质水平及哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)信号通路的蛋白质水平变化;使用细胞荧光免疫检测过表达或干扰ASCT2后ASCT2和Ki67的表达情况;使用平板克隆与MTT法检测ASCT2对胃癌细胞增殖的影响。结果相比于胃黏膜上皮细胞系GES1,ASCT2在人类胃癌细胞系MGC803、SGC7901、AGS、BGC823、HGC27、MKN28和MKN45中具有高转录以及蛋白质表达水平,在AGS、SGC7901和MGC803中成功过表达和沉默ASCT2。在AGS和SGC7901中过表达ASCT2后,Ki67的荧光强度大幅增加。沉默ASCT2显著抑制SGC7901 (P=0.008,P<0.001)和MGC803(P<0.001,P=0.067)细胞的生长及克隆形成;过表达ASCT2则显著促进SGC7901 (P=0.001,P=0.003)和MGC803 (P=0.002,P=0.014)细胞的生长及克隆形成。在AGS、SGC7901和MGC803中过表达ASCT2后,mTOR信号通路被激活并上调下游基因的表达;而沉默ASCT2后,抑制mTOR信号通路与其下游基因的表达。结论 ASCT2能通过mTOR信号通路显著促进胃癌细胞的生长。

Objective To investigate the effect of amino-acid transporter 2(ASCT2)on the development and progression of gastric carcinoma and the underlying molecular mechanisms.Methods ASCT2 was up-regulated by transient over-expression or down-regulated by short hairpin RNA(shRNA).The protein level changes of ASCT2 and mammalian target of rapamycin(mTOR)signaling pathway after ASCT2 over-expression or silencing were detected by Western blot.The expression of ASCT2 and Ki67 after over-expression or silencing were analyzed by immunofluorescence assay.The effect of ASCT2 on gastric cancer cell proliferation was examined by clone formation and MTT assays.Results Compared with the gastric epithelial cell line(GES1),ASCT2 has high transcription and protein expression levels in human gastric cancer cell lines MGC803,SGC7901,AGS,BGC823,HGC27,MKN28 and MKN45.Successfully over-expression and silencing of ASCT2 in gastric cancer cells such as AGS,SGC7901 and MGC803.After ASCT2 was over-expressed in AGS and SGC7901,the fluorescence intensity of Ki67 increased significantly.ASCT2 silencing significantly inhibited cell growth and cell clonal formation of SGC7901(P=0.008,P<0.001)and MGC803(P<0.001,P=0.067),while ASCT2 over-expression significantly promoted cell growth and cell clonal formation of SGC7901(P=0.001,P=0.003)and MGC803(P=0.002,P=0.014).ASCT2 over-expression in AGS,SGC7901 and MGC803 resulted in the activation of mTOR signaling pathway and the expressions of downstream genes,while ASCT2 silencing inhibited the expression of the mTOR signaling pathway and its downstream genes.Conclusions ASCT2 can significantly promote the growth of gastric cancer through mTOR signaling pathway.