Karsy Michael, Albert Ladislau, Murali Raj, Jhanwar-Uniyal Meena
Department of Neurosurgery, University of Utah, 175 North Medical Dr. East, Salt Lake City, UT, 84132, USA,
Tumour Biol. 2014 May;35(5):4567-80. doi: 10.1007/s13277-013-1601-6. Epub 2014 Jan 8.
Glioblastoma (GBM) is the most common primary brain tumor in adults and demonstrates a 1-year median survival time. Codon-specific hotspot mutations of p53 result in constitutively active mutant p53, which promotes aberrant proliferation, anti-apoptosis, and cell cycle checkpoint failure in GBM. Recently identified CD133(+) cancer stem cell populations (CSC) within GBM also confer therapeutic resistance. We studied targeted therapy in a codon-specific p53 mutant (R273H) created by site-directed mutagenesis in U87MG. The effects of arsenic trioxide (ATO, 1 μM) and all-trans retinoic acid (ATRA, 10 μM), possible targeted treatments of CSCs, were investigated in U87MG neurospheres. The results showed that U87-p53(R273H) cells generated more rapid neurosphere growth than U87-p53(wt) but inhibition of neurosphere proliferation was seen with both ATO and ATRA. U87-p53(R273H) neurospheres showed resistance to differentiation into glial cells and neuronal cells with ATO and ATRA exposure. ATO was able to generate apoptosis at high doses and proliferation of U87-p53(wt) and U87-p53(R273H) cells was reduced with ATO and ATRA in a dose-dependent manner. Elevated pERK1/2 and p53 expression was seen in U87-p53(R273H) neurospheres, which could be reduced with ATO and ATRA treatment. Additionally, differential responses in pERK1/2 were seen with ATO treatment in neurospheres and non-neurosphere cells. In conclusion, codon-specific mutant p53 conferred a more aggressive phenotype to our CSC model. However, ATO and ATRA could potently suppress CSC properties in vitro and may support further clinical investigation of these agents.
胶质母细胞瘤（GBM）是成人中最常见的原发性脑肿瘤，其1年中位生存时间较短。p53密码子特异性热点突变会导致组成型活性突变型p53的产生，这会促进GBM中的异常增殖、抗凋亡以及细胞周期检查点功能障碍。最近在GBM中鉴定出的CD133(+)癌症干细胞群体（CSC）也具有治疗抗性。我们在通过定点诱变在U87MG中创建的密码子特异性p53突变体（R273H）中研究了靶向治疗。在U87MG神经球中研究了三氧化二砷（ATO，1μM）和全反式维甲酸（ATRA，10μM）这两种可能的CSC靶向治疗方法的效果。结果表明，U87-p53(R273H)细胞比U87-p53(wt)细胞产生更快的神经球生长，但ATO和ATRA均能抑制神经球增殖。暴露于ATO和ATRA时，U87-p53(R273H)神经球显示出对分化为神经胶质细胞和神经元细胞的抗性。高剂量时ATO能够诱导凋亡，并且ATO和ATRA以剂量依赖的方式降低U87-p53(wt)和U87-p53(R273H)细胞的增殖。在U87-p53(R273H)神经球中可见pERK1/2和p53表达升高，而ATO和ATRA处理可使其降低。此外，在神经球和非神经球细胞中，ATO处理对pERK1/2有不同的反应。总之，密码子特异性突变型p53赋予我们的CSC模型更具侵袭性的表型。然而，ATO和ATRA在体外可有效抑制CSC特性，可能支持对这些药物进行进一步的临床研究。
