Article

Allele-Specific p53 Mutant Reactivation

The Cancer Institute of New Jersey, New Brunswick, NJ 08903, USA.
Cancer cell (Impact Factor: 23.89). 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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    • "If ZMC1 is a Zn 21 ionophore and the source of the Zn 21 it delivers is extracellular, as suggested by our kinetic experiments in Zn 21 -free media, then depleting the extracellular Zn 21 from complete media should inhibit ZMC1's function. To test this prediction, we took advantage of ZMC1's known ability to induce a conformational change in p53- R175H using the conformation specific antibodies PAB240 and PAB1620 in complete media with and without Zn 21 chelators (Fig. 5A) (Yu et al., 2012). Consistent with previous results, ZMC1 treatment shifted the p53-R175H immunophenotype from misfolded (PAB240) to WT-like (PAB1620) in TOV112D cells in untreated media (Yu et al., 2012). "
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    ABSTRACT: p53 is a Zn(2+)-dependent tumor suppressor inactivated in >50% of human cancers. The most common mutation, R175H, inactivates p53 by reducing its affinity for the essential zinc ion, leaving the mutant protein unable to bind the metal in the low [Zn(2+)]free environment of the cell. The exploratory cancer drug ZMC1 was previously demonstrated to reactivate this and other Zn(2+)-binding mutants by binding Zn(2+) and buffering it to a level such that Zn(2+) can repopulate the defective binding site, but how it accomplishes this in the context of living cells and organisms is unclear. Here, we demonstrate that ZMC1 increases intracellular [Zn(2+)]free by functioning as a zinc ionophore. ZMC1 binds Zn(2+) in the extracellular environment, diffuses across the plasma membrane as the neutral complex, and releases zinc into the cell once again as the Zn(2+) ion. It raises intracellular [Zn(2+)]free in cancer (TOV112D) and non-cancer (HEK293) cell lines to 15.8 and 18.1 nM, respectively, with half times of 2-3 min. These [Zn(2+)]free are predicted to result in ~90% saturation of p53-R175H, thus accounting for its observed reactivation. This mechanism is supported by the x-ray crystal structure of the [Zn(ZMC1)2] complex, which demonstrates structural and chemical features consistent with those of known metal ionophores. These findings provide a physical mechanism linking ZMC1's in vitro and in vivo activities, and define the remaining critical parameter necessary for developing synthetic metallochaperones for clinical use. The American Society for Pharmacology and Experimental Therapeutics.
    Molecular pharmacology 02/2015; 87(5). DOI:10.1124/mol.114.097550 · 4.12 Impact Factor
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    • "The potential use of zinc to recover wild-type folding has therefore been explored and this approach has been shown to restore chemosensitivity to anticancer drugs in cells expressing endogenous mutant p53 (Puca et al., 2011). In addition, the thiosemicarbazone metal ion chelator NSC31926 was found to restore wild-type function in a variety of different mutant p53-expressing cell lines, possibly through increasing the bioavailability of zinc to (mutant) p53 (Yu et al., 2012). Of all the compounds that restore wild-type activity, the most progress has been made with PRIMA-1 analogs, with the "
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    ABSTRACT: Many different types of cancer show a high incidence of TP53 mutations, leading to the expression of mutant p53 proteins. There is growing evidence that these mutant p53s have both lost wild-type p53 tumor suppressor activity and gained functions that help to contribute to malignant progression. Understanding the functions of mutant p53 will help in the development of new therapeutic approaches that may be useful in a broad range of cancer types.
    Cancer cell 03/2014; 25(3):304-317. DOI:10.1016/j.ccr.2014.01.021 · 23.89 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