Abstract 3745: Mechanisms of HIF2-mediated small intestine radioprotection

Abstract

Abstract Pancreatic cancer is the fourth-leading cause of cancer-related deaths in the United States, and it is projected to become the second by 2030. The 5-year overall survival rate for locally advanced pancreatic cancer (LAPC) remains < 5%. Chemotherapy regimens often fail due to poor drug delivery and penetration into the tumor. Because surgery is not feasible by definition in LAPC, radiation therapy (RT) is the only option to achieve local control. However, irradiating the pancreas is challenging because potentially curative doses are limited by the neighboring small intestine, which can only tolerate a maximum of 50Gy. A selective radioprotector of the intestinal tract could allow pancreatic cancer patients to receive a higher, and potentially definitive, dose of radiation by increasing the duodenum’s tolerance to survive radiation injury. The EGLN prolyl hydroxylases are cellular oxygen sensors that regulate cell survival and metabolism through the degradation of hypoxia-inducible factors (HIFs) in the presence of oxygen. Our group has shown that HIF2 stabilization through genetic or pharmacologic inhibition of the EGLN family prevents death from radiation-induced gastrointestinal toxicity in mice without protecting the primary tumor. To understand the mechanism by which HIF2 mediates this protection, we generated intestinal organoids from mice with a Cre-inducible allele that expresses a non-degradable form of human HIF1 or HIF2. Whole transcriptomic analysis revealed HIF1 and HIF2 have distinct gene responses in the small intestinal crypt. HIF2 induced the expression of known radiation modulators and genes involved in oxidative damage response, tissue healing, and intestinal homeostasis such as the non-canonical Wnt5a. We validated HIF2 drives Wnt5a expression in multiple organoid model systems. We then generated knockouts (KO) of Wnt5a or Ror2, its cognate receptor, using the Cre/lox system to test if Wnt5a is necessary and sufficient for radioprotection. By using the spheroid formation assay, a modified clonogenic assay, we found Wnt5a KO organoids had decreased crypt regeneration following RT. Our preliminary data suggest Wnt5a protects the duodenum from RT by increasing intestinal stem cell survival. Citation Format: Carolina J. Garcia Garcia, Suman Govindaraju, Marimar de la Cruz Bonilla, Cullen M. Taniguchi. Mechanisms of HIF2-mediated small intestine radioprotection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3745.