Allele-specific p53 mutant reactivation.

The Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA.
Cancer cell (Impact Factor: 25.29). 05/2012; 21(5):614-25. DOI: 10.1016/j.ccr.2012.03.042
Source: PubMed

ABSTRACT Rescuing the function of mutant p53 protein is an attractive cancer therapeutic strategy. Using the National Cancer Institute's anticancer drug screen data, we identified two compounds from the thiosemicarbazone family that manifest increased growth inhibitory activity in mutant p53 cells, particularly for the p53(R175) mutant. Mechanistic studies reveal that NSC319726 restores WT structure and function to the p53(R175) mutant. This compound kills p53(R172H) knockin mice with extensive apoptosis and inhibits xenograft tumor growth in a 175-allele-specific mutant p53-dependent manner. This activity depends upon the zinc ion chelating properties of the compound as well as redox changes. These data identify NSC319726 as a p53(R175) mutant reactivator and as a lead compound for p53-targeted drug development.

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    ABSTRACT: Reactivation of wild-type p53 (wt-p53) function is an attractive therapeutic approach to p53-defective cancers. An ideal p53-based gene therapy should restore wt-p53 production and reduces mutant p53 transcripts simultaneously. In this study, we described an alternative strategy named as trans-splicing that repaired mutant p53 transcripts in hepatocellular carcinoma (HCC) cells. The plasmids which encoded a pre-trans-splicing molecule (PTM) targeting intron 6 of p53 were constructed and then transfected into HCC cells carrying p53 mutation. Phenotypic changes of HCC cells induced by p53-PTM were analyzed through cell cycle, cell apoptosis and the expression of p53 downstream target genes. Spliceosome mediated RNA trans-splicing (SMaRT) reduced mutant p53 transcripts and produced functional wt-p53 protein after the delivery of p53-PTM plasmids, which resulted in phenotype correction of HCC cells. In tumor xenografts established by p53-mutated HCC cells, adenovirus encoding p53-PTM induced cell cycle arrest and apoptosis and then blocked the growth of tumors in mice. Collectively, our results demonstrated for the first time that mutant p53 transcripts were functionally corrected in p53-defective HCC cells and xenografts using trans-splicing, which indicated the feasibility of using trans-splicing to repair p53 mutation in p53-defective cancers.
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    ABSTRACT: Many oncogenic mutations inactivate the tumor suppressor p53 by destabilizing it, leading to its rapid aggregation. Small molecule drugs are being developed to stabilize such mutants. The kinetics of aggregation of p53 is deceptively simple. The initial steps in the micromolar concentration range follow apparent sigmoidal sequential first-order kinetics, with rate constants k1 and k2. However, the aggregation kinetics of a panel of mutants prepared for Φ-value analysis has now revealed a bimolecular reaction hidden beneath the observed first-order kinetics. Φu measures the degree of local unfolding on a scale of 0-1. A number of sequential Φu-values of ∼1 for k1 and k2 over the molecule implied more than one protein molecule must be reacting, which was confirmed by finding a clear concentration dependence at submicromolar protein. Numerical simulations showed that the kinetics of the more complex mechanism is difficult, if not impossible, to distinguish experimentally from simple first order under many reaction conditions. Stabilization of mutants by small molecules will be enhanced because they decrease both k1 and k2. The regions with high Φu-values point to the areas where stabilization of mutant proteins would have the greatest effect.
    Proceedings of the National Academy of Sciences 02/2015; DOI:10.1073/pnas.1500243112 · 9.81 Impact Factor
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    ABSTRACT: p53 Tumor suppressor gene encodes for a critical cellular protein that regulates the integrity of the cell and can induce cell cycle arrest and/or apoptosis upon cellular stresses of several origins, including chemotherapeutics. Loss of p53 function occurs in an estimated 50% of all cancers by mutations and deletions while in the presence of wild-type p53 alleles other mechanisms may affect the expression and activity of p53. Alternate mechanisms include methylation of the promoter of p53, deletion or epigenetic inactivation of the p53-positive regulator p14/ARF, elevated expression of the p53 regulators murine double minute 2 (MDM2) and MDMX, or alteration of upstream regulators of p53 such as the kinase ATM. MDM2 is a p53 E3 ubiquitin ligase that mediates the ubiquitin-dependent degradation of p53 while p14/ARF is a small MDM2-binding protein that controls the activity of MDM2 by displacing p53 and preventing its degradation. MDMX antagonize p53-dependent transcriptional control by interfering with p53 transactivation function. The understanding of the key role of p53 inactivation in cancer development generated considerable interest in developing compounds that are capable of restoring the p53 functions. Several patents have been issued on such compounds. Adenovirus-based p53 gene therapy as well as small molecules such as PRIMA that can restore the transcriptional transactivation function to mutant p53, or NUTLIN and RITA that interfere with MDM2-directed p53 degradation, have tested in a preclinical setting and some of these approaches are currently in clinical development.
    Topics in Anti-Cancer Research, Edited by Atta-ur-Rahman and Khurshid Zaman, 01/2012: chapter 1978-1-60805-612-5: pages 192-227; BENTHAM SCIENCE., ISBN: 978-1-60805-612-5

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