Molecular and Cellular Pathobiology A Novel Mouse Model to Study Image-Guided, Radiation-Induced Intestinal Injury and Preclinical Screening of Radioprotectors Ioannis I. Verginadis 1 , Rahul Kanade 1 , Brett Bell 1 , Sravya Koduri 2 , Edgar Ben-Josef 1 , and Constantinos Koumenis 1 Abstract Radiation is an important treatment modality for gastroin- testinal tumors, but intestinal injury is a common side effect. Here we describe a physiologically relevant model for studying the molecular determinants of radiation-induced intestinal damage and testing novel radioprotectors. The model employs a radiopaque marker implanted into the surface of the mouse jejunum, serving as a fiducial marker for precise radiation targeting. Mice were imaged with Cone-Beam CT (CBCT) and irradiated (IR) to the marked area using the Small Animal Radiation Research Platform (SARRP). IR-induced damage was acute but reversible and largely restricted to the area of the marker, leaving the surrounding tissues intact. Although whole gut irradiation with these doses caused lethal GI syndrome, focal (5 mm) radiation of the intestine did not cause any weight loss or lethality. However, fibrosis and collagen deposition 4 months post-IR indicated chronic intestinal damage. A separate cohort of mice was treated daily with curcumin, a clinically tested radioprotector, prior to and post-IR. Curcumin-treated mice showed significant decreases in both local and systemic inflam- matory cytokine levels and in fibrosis, suggesting it is an effective radioprotector of the intestine. Our results indicate that this model, which emulates clinically relevant intestinal radiation- induced injury, can be used to assess radioprotectors prior to testing in the clinic. Cancer Res; 77(4); 908–17. Ó2016 AACR. Introduction Radiotherapy is an important modality in cancer treatment with approximately half of all cancer patients receiving radiother- apy during the course of their treatment (1). As many patients receiving radiotherapy for abdominal or pelvic malignancies experience some form of radiation-induced gastrointestinal inju- ry, there is great interest in understanding the mechanisms behind this pathology and developing effective treatments for it (2). In addition, there is increased concern regarding intentional or accidental exposure of humans to large doses of ionizing radia- tion due to the onset of acute radiation syndrome (ARS). ARS is comprised of three phases: the hematopoietic phase, gastrointes- tinal phase, and neurovascular phase in a dose-dependent order (3). Therapies currently exist to manage the hematopoietic phase, although no significant countermeasures exist to address the gastrointestinal or neurovascular phases at this time. At present, animal models for targeted irradiation (IR) of the small intestine, which mimic clinical patient care, are scarce. This is due to the fact that the prevailing models require either whole body or abdominal irradiation, or require a surgical exterior- ization of the small intestine. A more physiologically relevant model, which does not require repeated surgeries, was developed by Hauer-Jensen and colleagues involving transposition of a loop of the ileum to the animal's scrotum, allowing local irradiation of that segment (4). However, this model may only be used on segments of the gastrointestinal tract in close proximity to the scrotum. The model described in this article allows for targeted in situ irradiation of small intestinal segments. Moreover, the model only requires a single, minimally invasive surgery, which is used to place radiopaque markers for image-guided radiation. In addi- tion, multiple fractions of conformally delivered irradiation may be administered without additional surgical intervention. This model is essential for understanding the pathophysiology of radiation injury, and testing potential novel radioprotectors and mitigators to improve cancer radiotherapy and be able to respond to radiologic incidents. One potential radioprotective agent for the small intestine is curcumin, the principal curcuminoid of turmeric (Curcuma longa). Curcumin has a long history of use in traditional medicine. It is known to have oxygen radical–scavenging abilities as well as anti- inflammatory actions during a damage response (5). We and other groups have shown that it acts as a radiosensitizer in cancerous tissue while acting as a radioprotector in normal tissue (5, 6). Furthermore, it has a low toxicity profile with humans being able to tolerate at least 12 g per day of oral curcumin (7). Although curcumin exhibits low bioavailability in plasma, it shows the highest concentration in the gastrointestinal tract after oral gavage treatment (8). Along these lines, curcumin has been shown to be a radioprotector in the ileum when administered orally (9, 10). Therefore, we tested the ability of curcumin to 1 Department of Radiation Oncology, The Perelman School of Medicine, Univer- sity of Pennsylvania, Philadelphia, Pennsylvania. 2 Department of Biology, Drexel University, Philadelphia, Pennsylvania. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Corresponding Author: Constantinos Koumenis, University of Pennsylvania School of Medicine, SCTR Bldg Room 8-087, 3400 Civic Center Blvd, Philadel- phia, PA 19104-5156. Phone: 215-898-0076; Fax: 215-898-0090; E-mail: costas.koumenis@uphs.upenn.edu doi: 10.1158/0008-5472.CAN-16-2724 Ó2016 American Association for Cancer Research. 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