Abstract 1447: Influence of IL-17-secreting immune cells in pancreatic cancer stemness
Authors: Zhang Yu , Sahin Ismet , Gupta Sonal , Maitra Anirban , Bailey Jennifer , Leach Steven , McAllister Florencia 
Published: July 2016

Abstract
Little is known about how the immune system influences pancreatic cancer stemness. Using a murine model of pancreatic intraepithelial neoplasia (PanIN), we have previously reported that KrasG12D induces expression of IL-17 receptors (IL-17RA) on emerging PanINs, as well as pancreatic infiltration by IL-17-producing CD4+ and gamma-delta-T cells. Forced IL-17 over-expression dramatically accelerates PanIN initiation and progression, while inhibition of IL-17 signaling using either genetic or pharmacologic techniques effectively prevents PanIN formation. When IL-17 signaling was blocked using monoclonal antibodies on transgenic mice harboring PanINs, transcriptional analysis of Kras-mutated epithelial cells revealed significant down-regulation of multiple stemness-related genes: doublecortin-like kinase 1 (Dclk1) [2], Trefoil factor 1 (Tff1)[3], Sonic Hedgehog (SHH) [4], and others. Dclk1 has been recently described as a marker of tumor initiating cells and its functional role in cancer initiation and development is currently being studied. We found that adenovirus mediated-IL-17 overexpression in the murine pancreas harvesting Kras mutation results in PanINs with significantly higher number of Dclk1+ cells that PanINs generated in the presence of a luciferase control virus. Reversely, the genetic ablation of IL-17 in the hematopoietic compartment of the same type of mice resulted in PanINs with significantly lower number of Dclk1+ cells when compared with PanINs from mice transplanted with wild type (WT) bone marrow. We have found that in vitro stimulation of KPC cells (obtained from KrasG12D/+; LSL- Trp53R172H/+; Pdx1−Cre mice) with IL-17A results in direct induction of Dclk1, Aldh1 and SHH protein expression in a time-dependent and dose-dependent fashion, validating the results of our gene microarray in a different system and at the protein level. Furthermore, we have found that one of the mechanisms by which IL-17 induces Dclk-1 and ALDH1a1 is through activation of NF-KB canonical pathway. We found that IL-17 had no effect in KPC cells proliferation in 2D culture. However, stimulation of matrigel embedded- KPC cells with IL-17A resulted in significant increase in tumorspheres formation in vitro. But even more important, KPC cells in vitro incubated with IL-17A for 7 days have accelerated capacity for in vivo- tumor initiation when injected subcutaneously into syngeneic immune-competent mice, confirming the functional in vivo role that IL-17-immune secreting cells have in inducing pancreatic cancer stemness. Better understanding of the regulation that IL-17-secreting immune cells can impose on pancreatic cancer- tumor initiating cells would be of high importance given the potential translational value of blocking IL-17 signaling for pancreatic cancer prevention and treatment with the currently available IL-17 neutralizing monoclonal antibodies.
Citation Format: Yu Zhang, Ismet Sahin, Sonal Gupta, Anirban Maitra, Jennifer Bailey, Steven Leach, Florencia McAllister. Influence of IL-17-secreting immune cells in pancreatic cancer stemness. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1447.