Abstract IA22: Innate immune cell PI3K gamma as a target for suppression of pancreatic ductal adenocarcinoma

Abstract

Abstract Ductal adenocarcinoma of the pancreas (PDAC) is a devastating disease that will afflict greater than 40,000 Americans. Less than 5% of these new pancreatic cancer patients will survive 5 years following diagnosis. PDAC is rarely detected in the early stages, with more than 80% of patients presenting with locally unresectable or metastatic disease at the time of diagnosis. As this form of cancer is also resistant to current cytotoxic therapies and ionizing radiation, novel therapeutic and diagnostic approaches are desperately needed to improve patient outcome. A characteristic feature of PDAC is the presence of an abundant, inflammatory infiltrate. In response to tumor-derived chemoattractants, we found that myeloid cells invade tumors where they promote immunosuppression, resulting in tumor growth and metastasis. We discovered that myeloid cell PI3-kinase gamma (PI3Kgamma) controls tumor immunosuppression, as PI3Kgamma signaling inhibits pro-inflammatory gene expression responses in macrophages, monocytes and granulocytes and promotes anti-inflammatory responses. Suppression of PI3Kgamma in mutant mice and in mice treated with pharmacologic inhibitors of PI3Kgamma promotes CD8+ T cell anti-tumor immune responses, leading to a 50% reduction in tumor growth and metastasis in orthotopic mouse models of pancreatic carcinoma and significant extension of survival in GEM models of PDAC (PDX1-cre; LSL-KrasG12D/+; LSL-Trp53 R172H/+). Furthermore, PI3Kgamma inhibition blocks macrophage stimulation of collagen deposition by fibroblasts in PDAC. We are exploring the combination of PI3kinase gamma inhibition with tumor cell and T cell targeted therapeutics could significantly reduce tumor growth and metastasis of PDAC. These approaches could improve patient outcomes by reducing tumor progression and preserving organ function by inhibiting desmoplasia. Citation Format: Megan Kaneda, Chanae Hardamon, Michael C. Schmid, Michael Bouvet, Franco Novelli, Emilio Hirsch, Andrew Lowy, Judith A. Varner. Innate immune cell PI3K gamma as a target for suppression of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr IA22.