2-2-bis(hydroxymethyl)-1-azabicyclo(2-2-2-)octan-3-one and stictic-acid

The guardian of the genome, p53, is the most mutated protein found in all cancer cells. Restoration of wild-type activity to mutant p53 offers promise to eradicate cancer cells using novel pharmacological agents. Several molecules have already been found to activate mutant p53. While the exact mechanism of action of these compounds has not been fully understood, a transiently open pocket has been identified in some mutants. In our study, we docked twelve known activators to p53 into the open pocket to further understand their mechanism of action and rank the best binders. In addition, we predicted the absorption, distribution, metabolism, excretion and toxicity properties of these compounds to assess their pharmaceutical usefulness. Our studies showed that alkylating ligands do not all bind at the same position, probably due to their varying sizes. In addition, we found that non-alkylating ligands are capable of binding at the same pocket and directly interacting with Cys124. The comparison of the different ligands demonstrates that stictic acid has a great potential as a p53 activator in terms of less adverse effects although it has poorer pharmacokinetic properties.

Topics: Alkylation; Amifostine; Aza Compounds; Bridged Bicyclo Compounds, Heterocyclic; Drug Evaluation, Preclinical; Ellipticines; Heterocyclic Compounds, 4 or More Rings; Humans; Kinetics; Ligands; Mercaptoethylamines; Molecular Dynamics Simulation; Mutagenesis, Site-Directed; Mutation; Oxepins; Protein Binding; Pyrimidines; Quinuclidines; Tumor Suppressor Protein p53

The tumour suppressor p53 is the most frequently mutated gene in human cancer. Reactivation of mutant p53 by small molecules is an exciting potential cancer therapy. Although several compounds restore wild-type function to mutant p53, their binding sites and mechanisms of action are elusive. Here computational methods identify a transiently open binding pocket between loop L1 and sheet S3 of the p53 core domain. Mutation of residue Cys124, located at the centre of the pocket, abolishes p53 reactivation of mutant R175H by PRIMA-1, a known reactivation compound. Ensemble-based virtual screening against this newly revealed pocket selects stictic acid as a potential p53 reactivation compound. In human osteosarcoma cells, stictic acid exhibits dose-dependent reactivation of p21 expression for mutant R175H more strongly than does PRIMA-1. These results indicate the L1/S3 pocket as a target for pharmaceutical reactivation of p53 mutants.

Topics: Apoptosis Regulatory Proteins; Aza Compounds; Binding Sites; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Computational Biology; Cyclin-Dependent Kinase Inhibitor p21; Cysteine; Heterocyclic Compounds, 4 or More Rings; Humans; Molecular Dynamics Simulation; Mutant Proteins; Oxepins; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; Proto-Oncogene Proteins; Reproducibility of Results; Structure-Activity Relationship; Transcription, Genetic; Tumor Suppressor Protein p53