Targeted Inhibition of DNA-PKcs, ATM, ATR, PARP, and Rad51 Modulate Response to X Rays and Protons.

Authors

Scott J Bright
David B Flint
David K J Martinus
Broderick X Turner
Mandira Manandhar
Mariam Ben Kacem
Conor H McFadden
Timothy A Yap
Simona F Shaitelman
Gabriel O Sawakuchi

Publication Date

10-1-2022

Journal

Radiation Research

Abstract

Small molecule inhibitors are currently in preclinical and clinical development for the treatment of selected cancers, particularly those with existing genetic alterations in DNA repair and DNA damage response (DDR) pathways. Keen interest has also been expressed in combining such agents with other targeted antitumor strategies such as radiotherapy. Radiotherapy exerts its cytotoxic effects primarily through DNA damage-induced cell death; therefore, inhibiting DNA repair and the DDR should lead to additive and/or synergistic radiosensitizing effects. In this study we screened the response to X-ray or proton radiation in cell lines treated with DDR inhibitors (DDRis) targeting ATM, ATR, DNA-PKcs, Rad51, and PARP, with survival metrics established using clonogenic assays. We observed that DDRis generate significant radiosensitization in cancer and primary cells derived from normal tissue. Existing genetic defects in cancer cells appear to be an important consideration when determining the optimal inhibitor to use for synergistic combination with radiation. We also show that while greater radiosensitization can be achieved with protons (9.9 keV/µm) combined with DDRis, the relative biological effectiveness is unchanged or in some cases reduced. Our results indicate that while targeting the DDR can significantly radiosensitize cancer cells to such combinations, normal cells may also be equally or more severely affected, depending on the DDRi used. These data highlight the importance of identifying genetic defects as predictive biomarkers of response for combination treatment.

Keywords

Ataxia Telangiectasia Mutated Proteins, DNA, DNA Damage, DNA Repair, Humans, Neoplasms, Poly(ADP-ribose) Polymerase Inhibitors, Protons, Rad51 Recombinase, Radiation-Sensitizing Agents, X-Rays

Comments

Associated Data

PMID: 35939823