A critical role of MYC for transformation of human cells by HPV16 E6E7 and oncogenic HRAS
A critical role of MYC for transformation of human cells by HPV16 E6E7 and oncogenic HRAS
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DOI：
10.1093/carcin/bgs104
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发表时间：
2012-04-01
期刊：
影响因子：
4.7
通讯作者：
Kiyono, Tohru
中科院分区：
文献类型：
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作者：
Narisawa-Saito, Mako;Inagawa, Yuki;Kiyono, Tohru
人乳头瘤病毒（HPV）是宫颈癌发展的主要致病因子，并且两种病毒癌基因E6和E7的失调表达被认为有助于疾病的起始。最近，我们已经证明，致癌的HRAS（HRAS（G12 V））和MYC与HPV 16 E6 E7一起转导足以使正常人宫颈角质形成细胞（HCKs）发生致瘤性转化。在这里，我们表明，转导HRAS（G12 V）的E6 E7表达的背景下，导致积累的MYC蛋白和致瘤性转化，不仅正常的HCK，但也包括其他正常的原代人类细胞，包括舌角质形成细胞和支气管上皮细胞以及hTERT永生化的包皮成纤维细胞。皮下移植少至200个表达E6 E7和HRAS（G12 V）的HCK导致在2个月内肿瘤形成。解剖RAS信号通路，AKT 1或MEK 1的组成型活性形式不会导致E6 E7的肿瘤形成，但添加MYC诱导了致瘤性转化。增加MYC表达赋予对钙和血清诱导的终末分化的抗性，并激活哺乳动物雷帕霉素靶蛋白（mTOR）通路。mTOR抑制剂（雷帕霉素）和MYC抑制水平不影响培养物中的增殖，这两种抑制剂都显著抑制了表达E6 E7和HRAS（G12 V）的HCK的肿瘤形成。这些结果表明，在E6 E7表达失调的背景下，HRAS的单个突变可能是致癌的，并且MYC在与RAS信号通路的合作中在肿瘤发生中起关键作用。因此，MYC和/或下游mTOR通路的抑制可能不仅是MYC改变的癌症的治疗策略，而且也是RAS激活的癌症的治疗策略。
Human papillomaviruses (HPVs) are the primary causal agents for development of cervical cancer, and deregulated expression of two viral oncogenes E6 and E7 is considered to contribute to disease initiation. Recently, we have demonstrated that transduction of oncogenic HRAS (HRAS(G12V)) and MYC together with HPV16 E6E7 is sufficient for tumorigenic transformation of normal human cervical keratinocytes (HCKs). Here, we show that transduction of HRAS(G12V) on the background of E6E7 expression causes accumulation of MYC protein and tumorigenic transformation of not only normal HCKs but also other normal primary human cells, including tongue keratinocytes and bronchial epithelial cells as well as hTERT-immortalized foreskin fibroblasts. Subcutaneous transplantation of as few as 200 HCKs expressing E6E7 and HRAS(G12V) resulted in tumor formation within 2 months. Dissecting RAS signaling pathways, constitutively active forms of AKT1 or MEK1 did not result in tumor formation with E6E7, but tumorigenic transformation was induced with addition of MYC. Increased MYC expression endowed resistance to calcium- and serum-induced terminal differentiation and activated the mammalian target of rapamycin (mTOR) pathway. An mTOR inhibitor (Rapamycin) and MYC inhibition a level not affecting proliferation in culture both markedly suppressed tumor formation by HCKs expressing E6E7 and HRAS(G12V). These results suggest that a single mutation of HRAS could be oncogenic in the background of deregulated expression of E6E7 and MYC plays a critical role in cooperation with the RAS signaling pathways in tumorigenesis. Thus inhibition of MYC and/or the downstream mTOR pathway could be a therapeutic strategy not only for the MYC-altered but also RAS-activated cancers.