The impact of arsenic trioxide and all-trans retinoic acid on p53 R273H-codon mutant glioblastoma
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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-p53R273H cells generated more rapid neurosphere growth than U87-p53wt but inhibition of neurosphere proliferation was seen with both ATO and ATRA. U87-p53R273H 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-p53wt and U87-p53R273H cells was reduced with ATO and ATRA in a dose-dependent manner. Elevated pERK1/2 and p53 expression was seen in U87-p53R273H 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.
KeywordsGBM CSC MAPK ATO ATRA
This work was supported by an NYMC intramural grant, the Children’s Hospital Foundation Grant, the NYMC Departments of Pathology and Neurosurgery, and the NYMC Graduate School of Basic Medical Sciences. We would like to thank Dr. Wei Dai for his generous donation of a wild-type p53/pcDNA3.1 construct, Dr. Zeling Chau and Mr. Nicolaus Gulati for their assistance of generation and verification of the U87-p53R273H cell line, Dr. David Frick for support on amplification of the vector, and Dr. Fred Wu for assistance on U87 transfection and clone selection.
Conflicts of interest
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