Hepatitis B virus X protein overcomes oncogenic RAS-induced senescence in human immortalized cells
Hepatitis B virus X protein overcomes oncogenic RAS-induced senescence in human immortalized cells
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DOI：
10.1111/j.1349-7006.2007.00579.x
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发表时间：
2007-10-01
期刊：
影响因子：
5.7
通讯作者：
Murakami, Seishi
中科院分区：
文献类型：
--
作者：
Oishi, Naoki;Shilagardi, Khurts;Murakami, Seishi
慢性B型肝炎病毒（HBV）感染是肝细胞癌的主要危险因素。HBV X蛋白（HBx）被认为具有致癌潜力，尽管其分子机制仍不清楚。已经使用啮齿动物系统检查了HBx在致癌过程中的病理作用，并且没有关于HBx在体外人体细胞中致癌作用的报告。因此，我们研究了HBx对人原代细胞永生化和转化的影响。我们发现HBx可以克服活性RAS诱导的人永生化细胞衰老，这些细胞可以在软琼脂中形成集落，并在裸鼠体内形成肿瘤。然而，单独的HBx既不能促进这些细胞的永生化，也不能促进这些细胞的转化。在群体倍增分析中，HBx的N-末端截短突变体HBx-D1（氨基酸51-154），其具有共激活结构域，可以克服活性RAS诱导的细胞衰老，但这些细胞未能表现出集落形成和致瘤能力，可能是由于蛋白质的低表达水平。通过扫描簇丙氨酸取代突变体的HBx表达文库，发现N-末端结构域通过稳定全长HBx对于克服活性RAS诱导的衰老是关键的。这些结果有力地表明，HBx可以通过克服活性癌基因诱导的衰老而促进癌发生。
Chronic infection with hepatitis B virus (HBV) is a major risk factor for hepatocellular carcinoma. The HBV X protein (HBx) is thought to have oncogenic potential, although the molecular mechanism remains obscure. Pathological roles of HBx in the carcinogenic process have been examined using rodent systems and no report is available on the oncogenic roles of HBx in human cells in vitro. We therefore examined the effect of HBx on immortalization and transformation in human primary cells. We found that HBx could overcome active RAS-induced senescence in human immortalized cells and that these cells could form colonies in soft agar and tumors in nude mice. HBx alone, however, could contribute to neither immortalization nor transformation of these cells. In a population doubling analysis, an N-terminal truncated mutant of HBx, HBx-D1 (amino acids 51-154), which harbors the coactivation domain, could overcome active RAS-induced cellular senescence, but these cells failed to exhibit colonigenic and tumorigenic abilities, probably due to the low expression level of the protein. By scanning a HBx expression library of the clustered-alanine substitution mutants, the N-terminal domain was found to be critical for overcoming active RAS-induced senescence by stabilizing full-length HBx. These results strongly suggest that HBx can contribute to carcinogenesis by overcoming active oncogene-induced senescence.