Abstract 710: Post-exposure suppression of radiation pneumonitis suggests non-redundant independent effects of TGF-beta and TRAIL/DR5

Abstract Radiation pneumonitis is one of the most common but challenging toxicities seen in patients that are receiving ionizing radiotherapy for thoracic malignancies. While radiation effectively eliminates cancer cells, the damage it causes to surrounding healthy lung tissue leads to an immune response that can impact treatment regimen and lead to long term fibrotic tissue formation. The mechanism of radiation pneumonitis and the inflammatory response in the lungs is poorly understood. However, it is known that the TRAIL pathway plays an important role in inflammatory and fibrotic response. Through our previous work, it was discovered that modulating the TRAIL pathway via pegylated recombinant long-acting TRAIL (TLY012) in both WT and TRAIL-/- C57Bl/6 could suppress radiation pneumonitis in mice that were exposed to 20 Gy of thoracic radiation with shielding of other organs as early two weeks post exposure. In addition to the TRAIL pathway, transforming growth factor-beta (TGF-β) is a cytokine that is known to play a key role in fibrosis. Broad spectrum integrin inhibitor GLPG0187 is known to inhibit the activation of TGF-β via binding to specific integrin receptors. In order to determine if the inhibition of TGF-β could suppress radiation pneumonitis without stimulation of the TRAIL pathway, DR5 null mice were utilized for the experiment. Male DR5-/- C57Bl/6 mice received a single 20 Gy thoracic radiation dose with shielding of other organs and were treated with 100 mg/kg of GLPG-0187 or control twice a week via IP injection with the first dose being administered 1 hour before radiation (n = 4/treatment/group). 13 days post-irradiation, lungs, sternal bone marrow, and peripheral serum were collected. Upon histological analysis, it was observed that there were thinner alveolar borders and lessened inflammation compared to the control mice. Mice were weighed every three days, and it was discovered that mice treated with GLPG-0187 maintained steady weight compared to the control group. Additional analysis including immunohistochemistry, cytokine profiling, and quantification needs to be conducted. As the TRAIL pathway could not be modulated in the DR5 null mice, these findings suggest that GLPG-0187 was able to suppress radiation pneumonitis via inhibition of TGF-β. While some rescue from radiation pneumonitis was observed via GLPG0187, it was to a lesser extent compared to treatment of WT and TRAIL-/- C57Bl/6 mice with TLY012. Future directions include investigating the synergistic effects between TLY012 and GLPG0187 in suppressing radiation pneumonitis and decreasing fibrotic response to radiation. Citation Format: Jillian Strandberg, Anna Louie, William MacDonald, Praveen Srinivasan, Leiqing Zhang, Lanlan Zhou, Seulki Lee, Wafik El-Deiry. Post-exposure suppression of radiation pneumonitis suggests non-redundant independent effects of TGF-beta and TRAIL/DR5 abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 710.