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APR-246 reactivates mutant p53 by targeting cysteines 124 and 277

Qiang Zhang1, Vladimir J N Bykov1, Klas G Wiman2

  • 1Department of Oncology and Pathology, Cancer Center Karolinska (CCK), Karolinska Institutet, SE-17176, Stockholm, Sweden.

Cell Death & Disease
|April 20, 2018
PubMed

Insights

Researchers identified specific cysteine residues in the TP53 gene that are crucial targets for the cancer drug APR-246. This finding advances the development of new therapies to restore tumor suppressor function in cancer cells.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • The TP53 tumor suppressor gene is frequently inactivated in human cancers via missense mutations.
  • TP53 mutations result in protein unfolding, reduced thermostability, and loss of DNA binding and transcription factor functions.
  • Restoring tumor suppressor function of mutant p53 is a key strategy in cancer therapy.

Purpose of the Study:

  • To identify the specific binding targets of the mutant p53 reactivating compound APR-246 (PRIMA-1Met).
  • To elucidate the role of specific cysteine residues in APR-246-mediated p53 stabilization and functional restoration.
  • To provide insights for the rational design of novel mutant p53-targeting cancer therapeutics.

Main Methods:

  • In silico analysis to identify potential binding sites of APR-246's active metabolite, methylene quinuclidinone (MQ).
  • Site-directed mutagenesis to assess the role of specific cysteine residues (Cys124, Cys277) in p53 function.
  • Thermal shift assays to evaluate the thermostability of wild-type and mutant p53 proteins.
  • Cell-based assays to measure the functional restoration of mutant p53 in cancer cells treated with APR-246.

Main Results:

  • Cysteine 277 (Cys277) was identified as a primary binding target for MQ within the p53 core domain.
  • Cys277 is essential for MQ-mediated thermostabilization of wild-type, R175H, and R273H mutant p53 proteins.
  • Both Cys124 and Cys277 are required for APR-246-mediated functional restoration of the R175H mutant p53 in cellular models.

Conclusions:

  • Cys277 is a critical residue for APR-246's mechanism of action, particularly in stabilizing p53.
  • The combined involvement of Cys124 and Cys277 is necessary for restoring the tumor suppressor activity of specific mutant p53 forms.
  • These findings support the development of targeted therapies aimed at reactivating mutant p53, offering new avenues for cancer treatment.

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