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

Area of Science:

• Oncology
• Molecular Biology
• Radiotherapy

Background:

• Bladder cancer exhibits diverse molecular subtypes, impacting treatment response.
• DNA damage response (DDR) pathways are crucial for cancer cell survival after radiation.
• Targeting DDR offers a potential strategy to enhance radiotherapy efficacy.

Purpose of the Study:

• To investigate the radiosensitizing effects of DNA-PK and ATR inhibitors in bladder cancer.
• To analyze the impact of these inhibitors on DNA repair mechanisms.
• To determine the synergistic potential of combined DDR inhibition and ionizing radiation.

Main Methods:

• Utilized DNA-PK inhibitor AZD7648 and ATR inhibitor Ceralasertib on bladder cancer cell lines (SCaBER, J82, VMCUB-1).
• Assessed radiosensitization by measuring IC50 shifts with increasing ionizing radiation (IR) doses.
• Evaluated DNA repair inhibition using neutral comet assays and Western blot analysis for pathway-specific inhibition (DNA-PK pSer2056, CHK1 pSer317).
• Determined synergistic effects via clonogenic survival assays and Chou-Talalay method for combined index (CI) calculation.

Main Results:

• DNA-PK and ATR inhibitors demonstrated radiosensitizing effects across tested bladder cancer cell lines.
• Inhibitor treatment significantly retarded DNA repair post-IR.
• Western blots confirmed specific inhibition of DNA-PK and ATR pathways.
• Clonogenic assays revealed cell-line-dependent synergistic effects of combined DDR inhibition and IR.
• Chou-Talalay analysis confirmed synergistic CI values specific to drug and IR doses.

Conclusions:

• Pharmacological inhibition of DNA-PK and ATR effectively targets DDR pathways in bladder cancer cells.
• These inhibitors induce a significant radiosensitizing effect at nanomolar concentrations.
• Combined inhibition of DNA-PK/ATR with IR impairs bladder cancer cell survival, offering a promising therapeutic strategy.