Abstract 4911: NSCLC cells demonstrate differential mode of cell death in response to the combined treatment of radiation and a DNA-PKcs inhibitor

Abstract

Abstract Introduction: Lung cancers demonstrate the highest number of p53 mutations of any cancer with 70% of small cell lung cancers and 33% of adenocarcinomas containing a mutation. Loss of p53 function has been correlated with therapeutic resistance and poor clinical outcomes. Therefore, developing therapeutic strategies that specifically target p53 loss-of-function mutants is of the utmost importance. The purpose of this investigation is to explore whether p53 status has impact on the radio-sensitizing effect of a DNA-PKcs inhibitor (NU7441). Methods: Clonogenic surviving fraction analysis, DNA double strand break repair kinetics, cell cycle analysis, immunofluorescence, immunoblot, apoptosis and autophagy assays were used to investigate the mechanism of radiosensitization of NU7441 in NSCLC cell lines (A549, H1299, and H460) with differential levels of p53 expression. Results: NU7441 substantially inhibited the repair of IR-induced DNA double strand break (DSB) in all three cell lines. Clonogenic surviving fraction analysis reveals that NU7441 is a better radio-sensitizer in p53-deficient cells (H1299) when compared to p53-wild type cells (A549, H460). Combination of ionizing radiation (IR) and NU7441 leads to a more robust G2 arrest in A549 and H460 cells when compared to radiation treatment only. However, NU7441 and radiation preferentially induced mitotic arrest in H1299 consequently leading to a significant increase in mitotic catastrophe. Furthermore, NU7441 led to an increase in apoptosis rather than autophagy as the predominant cell death pathway in p53-deficient cells. Moreover, knockdown of p53 using siRNA sensitized A549 to NU7441+IR treatment. Conclusion: Our study clearly shows that NU7441, a novel DNA-PKcs inhibitor, is a potent radio-sensitizer in p53-dificient lung cancer cells and highlights the promise of NU7441 in targeted cancer treatment. Citation Format: Yu Lan, Zengfu Shang, Feng-Ming Hsu, Vasu Tumati, Benjamin P. Chen, Debabrata Saha. NSCLC cells demonstrate differential mode of cell death in response to the combined treatment of radiation and a DNA-PKcs inhibitor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4911. doi:10.1158/1538-7445.AM2014-4911