The Effect of AZD5153 on Radiosensitivity in Pancreatic Cancer Cells Through ATM-chk1 Pathway

Background: Radioresistance compromises pancreatic cancer radiotherapy outcomes, making the identification of radiosensitizing strategies a critical priority. AZD5153, a novel specific Bromodomain-containing protein 4 (BRD4) inhibitor, has demonstrated efficacy in relapsed/refractory solid tumors and lymphomas. Our research focuses on investigating the effect of AZD5153 on the radiotherapy sensitivity of human pancreatic cancer cells, and its underlying mechanisms. Methods: CCK-8 was used to detect the effect of AZD5153 on pancreatic cancer cell proliferation activity. The radiosensitizing effect of AZD5153 was determined by cell colony formation assay. Fow cytometry, western blot and immunofluorescence were performed to analyze cell cycle, apoptosis and protein expression following AZD5153 and/or radiotherapy treatment in pancreatic cancer cells. A Capan2 pancreatic cancer xenograft mouse model was established to validate the radiosensitizing effect of AZD5153 in vivo. Results: AZD5153 showed the anti-proliferative effects on Capan2 and PANC1 cells and significantly enhanced radiosensitivity in both cell lines. The in vivo experiments also demonstrated that the combination of AZD5153 and radiotherapy enhanced anti-tumor efficacy relative to monotherapy. Moreover, AZD5153 alone or combined with radiation caused G2/M phase cell cycle arrest, and increased H2AX phosphorylation with γ-H2AX foci formation, indicating that AZD5153 enhanced radiotherapy-induced DNA damage in pancreatic cancer cells. Further molecular mechanism study revealed that AZD5153 inhibited radiotherapy-activated ATM-chk1 pathway, suggesting that AZD5153 may enhance radiosensitivity by impairing DNA damage repair. Conclusion: Collectively, these results suggested that AZD5153 might be a promising radiosensitizing agent, and targeting the ATM-chk1 pathway may offer a novel therapeutic strategy to overcome radioresistance in pancreatic cancer.