Effective Radiosensitization of Bladder Cancer Cells by Pharmacological Inhibition of DNA-PK and ATR

• Published in: Biomedicines Vol. 10; no. 6; p. 1277
• Main Authors: Chughtai, Ahmed Ali, Pannhausen, Julia, Dinger, Pia, Wirtz, Julia, Knüchel, Ruth, Gaisa, Nadine T., Eble, Michael J., Rose, Michael
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 30.05.2022; MDPI
• Subjects: Ataxia; ATR; AZD7648; Bladder cancer; Cancer; Cancer therapies; Cell culture; Cell cycle; Cell survival; Ceralasertib; Chemotherapy; CHK1 protein; Clinical trials; Comet assay; Deoxyribonucleic acid; DNA; DNA damage; DNA repair; DNA-dependent protein kinase; DNA-PK; Ionizing radiation; Kinases; Laboratories; Phosphorylation; Proteins; Radiation therapy; Radiosensitization; targeted therapy; Tumor cell lines; Tumors; United States > US; Berlin Germany; Germany
• ISSN: 2227-9059; 2227-9059
• DOI: 10.3390/biomedicines10061277

This study aims at analyzing the impact of the pharmacological inhibition of DNA damage response (DDR) targets (DNA-PK and ATR) on radiosensitization of bladder cancer cell lines of different molecular/histological subtypes. Applying DNA-PK (AZD7648) and ATR (Ceralasertib) inhibitors on SCaBER, J82 and VMCUB-1 bladder cancer cell lines, we revealed sensitization upon ionizing radiation (IR), i.e., the IC50 for each drug shifted to a lower drug concentration with increased IR doses. In line with this, drug exposure retarded DNA repair after IR-induced DNA damage visualized by a neutral comet assay. Western blot analyses confirmed specific inhibition of targeted DDR pathways in the analyzed bladder cancer cell lines, i.e., drugs blocked DNA-PK phosphorylation at Ser2056 and the ATR downstream mediator CHK1 at Ser317. Interestingly, clonogenic survival assays indicated a cell-line-dependent synergism of combined DDR inhibition upon IR. Calculating combined index (CI) values, with and without IR, according to the Chou–Talalay method, confirmed drug- and IR-dose-specific synergistic CI values. Thus, we provide functional evidence that DNA-PK and ATR inhibitors specifically target corresponding DDR pathways retarding the DNA repair process at nano-molar concentrations. This, in turn, leads to a strong radiosensitizing effect and impairs the survival of bladder cancer cells.