Gain-of-Function Activity of Mutant p53 in Lung Cancer through Up-Regulation of Receptor Protein Tyrosine Kinase Axl.
Gain-of-Function Activity of Mutant p53 in Lung Cancer through Up-Regulation of Receptor Protein Tyrosine Kinase Axl.
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DOI：
10.1177/1947601912462719
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发表时间：
2012-07-01
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影响因子：
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通讯作者：
Deb, Sumitra
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作者：
Vaughan, Catherine A;Singh, Shilpa;Deb, Sumitra
p53突变存在于高达70%的肺癌中。一般来说，具有p53突变的癌细胞比具有野生型p53或没有p53的癌细胞生长得更积极。肿瘤衍生的突变型p53在细胞中的表达导致可能影响细胞生长和肿瘤发生的基因表达上调。在我们对这种侵袭性表型的研究中，我们研究了受体蛋白酪氨酸激酶Axl，其在表达突变体p53-R175 H、-R273 H和-D281 G的H1299肺癌细胞中在RNA和蛋白水平上被p53突变体上调。人肺癌细胞H1048（p53-R273 C）和H1437（p53-R267 P）中内源性突变体p53水平的敲低也导致Axl水平的降低。这种对Axl表达的影响对于p53的22和23位突变是不敏感的，表明p53的反式激活结构域可能在Axl基因表达的上调中不起关键作用。用乙酰化组蛋白抗体进行的染色质免疫沉淀（ChIP）测定证明突变体p53诱导Axl启动子区域上的组蛋白乙酰化。通过使用针对p53的抗体的ChIP测定证明Axl启动子上的直接突变体p53成核。Axl启动子具有p53/p63结合位点，然而其不是突变型p53介导的反式激活所必需的。通过Axl特异性RNAi敲低Axl导致功能获得性（GOF）活性降低，从而降低表达突变型p53的肺癌细胞中的细胞生长速率和运动速率。这表明对于具有突变型p53的肺癌细胞系，GOF活性部分地通过Axl介导。
p53 mutations are present in up to 70% of lung cancer. Cancer cells with p53 mutations, in general, grow more aggressively than those with wild-type p53 or no p53. Expression of tumor-derived mutant p53 in cells leads to up-regulated expression of genes that may affect cell growth and oncogenesis. In our study of this aggressive phenotype, we have investigated the receptor protein tyrosine kinase Axl, which is up-regulated by p53 mutants at both RNA and protein levels in H1299 lung cancer cells expressing mutants p53-R175H, -R273H, and -D281G. Knockdown of endogenous mutant p53 levels in human lung cancer cells H1048 (p53-R273C) and H1437 (p53-R267P) led to a reduction in the level of Axl as well. This effect on Axl expression is refractory to the mutations at positions 22 and 23 of p53, suggesting that p53's transactivation domain may not play a critical role in the up-regulation of Axl gene expression. Chromatin immunoprecipitation (ChIP) assays carried out with acetylated histone antibodies demonstrated induced histone acetylation on the Axl promoter region by mutant p53. Direct mutant p53 nucleation on the Axl promoter was demonstrated by ChIP assays using antibodies against p53. The Axl promoter has a p53/p63 binding site, which however is not required for mutant p53-mediated transactivation. Knockdown of Axl by Axl-specific RNAi caused a reduction of gain-of-function (GOF) activities, reducing the cell growth rate and motility rate in lung cancer cells expressing mutant p53. This indicates that for lung cancer cell lines with mutant p53, GOF activities are mediated in part through Axl.