Radiation and Cancer Biology

PD 07 - Biology 3 - Poster Discussion

1054 - A Computational Approach to Discovery of Novel Mutant p53 Reactivating Molecules As Targeted Radio-Sensitizing Agents for Head and Neck Cancer

Monday, October 22
4:15 PM - 4:21 PM
Location: Room 217 C/D

A Computational Approach to Discovery of Novel Mutant p53 Reactivating Molecules As Targeted Radio-Sensitizing Agents for Head and Neck Cancer
A. Nikolaev1, L. Zeng2, S. A. Spencer2, J. A. Bonner2, and E. S. Yang2; 1Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, AL, 2University of Alabama at Birmingham, Birmingham, AL

Purpose/Objective(s): p53 tumor suppressor plays a central role in the suppression of tumorigenesis by triggering cell growth arrest, apoptosis, and senescence in response to DNA damage, oxidative stress, and dysregulation of tumor oncogenes. Inactivation of p53 function by a gene mutation is present in the majority of human tumors and had been linked to genetic instability and malignant tumor progression. The goal of this project was to identify novel mutant p53 reactivating drug candidates that target the allosteric site of mutant p53, and to validate these candidate compounds in radio-sensitization assays in human head and neck cancer cells expressing both wild-type and mutant p53.

Materials/Methods: A publicly available database ZINC was used as a source of small molecule compounds in ready-to-dock 3D format for virtual screening. Mutant p53 R273H crystal structure obtained from Protein Data Bank. A multithreaded virtual screening tool for flexible ligand docking iDock was used for virtual screens. A protein ligand docking web service SwissDock was used for compound validation in docking studies. Apoptotic cell death following exposure to radiation was quantified by using the Annexin V-FITC apoptosis detection kit (Mountain View, CA) as previously described.

Results: To identify mutant p53 reactivating drug candidates, we took advantage of recent advances in computational structure-based drug design to perform a virtual screening of small molecule compound library against allosteric site within the R273H mutant p53 protein. A total of >800,000 compounds with drug-like properties were virtually screened against mutant p53 using an iDock tool. Purchasable compounds with the highest predicted negative free binding energies (iDock scores) were selected for further characterization from the top 1000 compounds identified in the virtual screen. The selected compounds were validated in molecular docking studies against mutant p53 structure using a protein ligand docking web service SwissDock. This approach resulted in identification of a total of 12 lead compounds with distinct chemical scaffolds that were selected for further experimental validation in radio-sensitization assays in both wild-type and mutant p53 expressing head and neck cancer cell lines. One of the identified small molecule leads is Compound 1, a quinazoline derivative with structural similarities to known mutant p53-reactivating drugs. The functional characterization of Compound 1, as well as other previously unknown classes of p53 reactivating candidate molecules in radio-sensitization assays will be presented.

Conclusion: Computational approach to discovery of mutant p53-reactivating agents yielded distinct classes of small molecule compounds with similarities to the known p53 reactivating molecules, as well as novel previously uncharacterized mutant p53 reactivating drug candidates. Radio-sensitizing properties of these compounds are evaluated in mutant p53 expressing head and neck cancer cells.

Author Disclosure: A. Nikolaev: None. L. Zeng: None. S.A. Spencer: None. J.A. Bonner: Honoraria; Bristol-Myers Squibb Company, Eli Lilly and Company, Merck Serono, Cel-Sci. Consultant; Bristol-Myers Squibb Company, Eli Lilly and Company, Merck Serono, Cel-Sci. Professor and Chairman; The University of Alabama at Birmingham. Immediate Past President; The University of Alabama Health Services Found. E.S. Yang: Research Grant; Aacr, Eli Lilly.

Anatoly Nikolaev, MD, PhD

Disclosure:
No relationships to disclose.

Biography:
Anatoly “Tony” Nikolaev, M.D., Ph.D., is currently a Holman Pathway resident at the Department of Radiation Oncology, University of Alabama at Birmingham. Prior to joining UAB, he completed a PhD thesis at Columbia University (New York), investigating the mechanisms of p53 tumor suppressor inactivation in human cancers. He subsequently completed a post-doctoral fellowship with the President of Stanford University, Dr. Marc Tessier-Lavigne (Palo Alto, CA), focusing on mechanisms of cell death and tumor angiogenesis. To gain a firsthand experience in the discovery and development of targeted cancer therapeutics, Tony joined a biotech giant Genentech (San Francisco, CA) as a principal investigator and lab scientist. While at Genentech, Tony had an opportunity to directly contribute to the pipeline cancer drug development projects, culminating in phase 1-2 clinical trials. While at UAB, Tony identified a Holman Pathway research mentor, Dr. Eddy Yang, M.D., Ph.D., a world renowned expert in the area of DNA damage response and repair, and received an intramural UAB pilot grant for computational approaches to discovery of mutant p53 reactivating drugs as targeted radio-sensitizing agents.

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