Abstract A49: Using IL10-/- mouse model to assess heavy-ion radiation exposure-associated colitis and colorectal cancer incidence

Underlying risk of γ-ray-induced colitis and colorectal cancer incidence is emphasized by the studies on atom bomb survivors and also in patients undergoing radiotherapy. However, uncertainties in colitis and CRC risk prediction after exposure to high-LET space (particle) radiation exposure has not been realized due to lack of reliable in vivo data. Here we report IL10-/- mice as a suitable mouse model for assessment of colitis and CRC risk after exposure to space radiation. Male mice (n=12 mice/group) were whole-body exposed to sham-radiation, γ-rays ( 137 Cs-source, 2.0 Gy), and 28 Si-ion (300 MeV/n; 70 keV/μm; 1.4 Gy). We used γ-ray equitoxic doses using relative biologic effectiveness (RBE) values determined earlier. Mice were sacrificed 90 days after irradiation, and colon swiss rolls were prepared and histopathologic assessment of colitis score and CRC grade was noted. Further, inflammation-associated gene-expression analysis was conducted in both radiation-induced tumor and adjoining normal tissue area. Immunohistochemistry (β-catenin, Cyclin-D1, and phospho-histone H3) was also performed to assess HZE-induced proliferative signaling. Relative to controls and γ-ray, colitis score, colon tumor incidence, size, and grade were significantly higher after space ( 28 Si-ion) radiation exposure. Additionally, tumor incidence per unit of radiation (per cGy) was also higher after 28 Si-ion radiation relative to γ radiation. Higher number of phospho-histone H3-positive cells in 28 Si-ion exposed mouse colon demonstrated increased proliferative index resulting in increased intestinal tumors of larger size and grade was due to greater activation of β-catenin and its downstream effector cyclin D1. Inflammatory gene signature was more pronounced after 28 Si-ion exposure. Significant upregulation of GATA4, ICAM1, ITGA2, and EGFR was exclusive to 28 Si-ion exposed mouse colon; however, PTGES and TGFβ1 were upregulated in both γ and 28 Si-ion exposed mice. Overall, our findings suggest that IL10 -/- mice are a suitable model to assess IR-induced colitis and CRC risk and space radiation carries higher risk of colitis and CRC incidence, relative to γ-rays at comparable doses. This study has implications for risk prediction in astronauts planning for deep-space missions and also for cancer patients planning to undergo particle radiotherapy. Citation Format: Shubhankar Suman, Bo-Hyun Moon, Albert J. Fornace, Jr., Kamal Datta. Using IL10-/- mouse model to assess heavy-ion radiation exposure-associated colitis and colorectal cancer incidence [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A49.