α4在化学致癌物诱导细胞转化中的作用

Function of α4 in human ce transformation induced by chemical carcinogens

目的：探讨α4在化学致癌物诱导细胞转化中的可能作用。方法：采用免疫印迹检测化学致癌物诱导既往转化细胞模型和肝肿瘤细胞株中α4的表达水平，再利用病毒感染法在肝永生化细胞株L02R上构建α4高表达（L02R-α4）和低表达（L02R-SHα4）的细胞株，检测其细胞生长速度和转化能力。进一步选择已建立的细胞株、化学致癌物AFB1诱导转化的细胞（L02RT-AFB1）及肝肿瘤细胞株HepG2和SMMC等，在有或无mTOR通路抑制剂雷帕霉素处理下，通过免疫印迹检测mTOR下游两个分子p70S6K1和4E-BP1的表达及磷酸化水平。结果：在化学致癌物诱导转化的细胞模型和肝肿瘤细胞株中发现α4的表达比对照细胞上调1.9~5.9倍。蛋白印迹结果证实L02R-α4和L02R-SHα4细胞株构建成功，α4表达上调能够促进L02R细胞增殖并发生转化（P＜0.05）。在α4高表达的转化细胞L02R-α4中，p70S6K1和4E-BP1呈高磷酸化状态。当有雷帕霉素作用时，所有细胞中p70S6K1和4E-BP1的磷酸化水平明显下降，在L02R-SHα4细胞中下降尤为显著。结论：α4具有癌基因功能，α4的异常上调激活mTOR通路，促进细胞增殖并诱导细胞恶性转化。

OBJECTIVE： To investigate the role for α4 in cell transformation induced by chemical carcinogens. METHODS：Immunoblotting was performed to examine the expression of α4 in chemical-transformed cells and tumor cell lines. Stable cell lines L02R-α4 and L02R-SHα4 were generated by infecting L02R cells with retroviral vectors encodingα4 or lentiviralα4 shRNA,respectively. Cell proliferation and anchorage-independent cell growth were examined in these cells. Immunoblotting analysis was applied to measure the phosphorylation status of p70S6K1 and 4E-BP1,which were the key members of mTOR pathway in established cells and transformed cell models L02RT-AFB1,HepG2,and SMMC with or without rapamycin treatment. RESULTS：The protein expression ofα4 in chemical-transformed cells and tumor cell lines increased by 1.9-5.9 fold compared with non-transformed cells. Immunoblotting results verified that L02R-α4 and L02R-SHα4 cells were successfully established. Ectopic expression 389ofα4 promoted cell growth and led to cell transformation. Notable increased phosphorylation levels of S6K1 （Thr ） and 37/464E-BP1 （Thr ） were observed in transformed cells where α4 was overexpressed. Upon rapamycin treatment, phosphorylation of p70S6K1 and 4E-BP1 declined significantly in all cells. Particularly,the effects were more profound in L02R-SHα4 cells. CONCLUSION：Overexpression ofα4 promoted cell proliferation and induced cell transformation via activation of mTOR signaling pathway.