Interleukin-15 stimulates natural killer cell-mediated killing of both human pancreatic cancer and stellate cells

// Jonas R.M. Van Audenaerde 1 , Jorrit De Waele 1 , Elly Marcq 1 , Jinthe Van Loenhout 1 , Eva Lion 2 , Johan M.J. Van den Bergh 2 , Ralf Jesenofsky 3 , Atsushi Masamune 4 , Geert Roeyen 5 , Patrick Pauwels 1, 6 , Filip Lardon 1 , Marc Peeters 1, 7 and Evelien L.J. Smits 1, 2 1 Center for Oncological Research, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium 2 Laboratory of Experimental Hematology, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium 3 Department of Medicine II, Medical Faculty of Mannheim, University of Heidelberg, Mannheim, Germany 4 Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai, Japan 5 Department of Hepatobiliary, Endocrine and Transplantation Surgery, Antwerp University Hospital, Antwerp, Belgium 6 Department of Pathology, Antwerp University Hospital, Antwerp, Belgium 7 Department of Oncology, Multidisciplinary Oncological Centre Antwerp, Antwerp University Hospital, Antwerp, Belgium Correspondence to: Jonas R.M. Van Audenaerde, email: jonas.vanaudenaerde@uantwerp.be Keywords: natural killer (NK) cells, pancreatic cancer (PDAC), pancreatic stellate cells (PSC), immunotherapy, interleukin-15 (IL-15) Received: March 14, 2017 Accepted: April 14, 2017 Published: May 25, 2017 ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is the 4 th leading cause of cancer-related death in Western countries with a 5-year survival rate below 5%. One of the hallmarks of this cancer is the strong desmoplastic reaction within the tumor microenvironment (TME), orchestrated by activated pancreatic stellate cells (PSC). This results in a functional and mechanical shield which causes resistance to conventional therapies. Aiming to overcome this resistance by tackling the stromal shield, we assessed for the first time the capacity of IL-15 stimulated natural killer (NK) cells to kill PSC and pancreatic cancer cells (PCC). The potency of IL-15 to promote NK cell-mediated killing was evaluated phenotypically and functionally. In addition, NK cell and immune checkpoint ligands on PSC were charted. We demonstrate that IL-15 activated NK cells kill both PCC and PSC lines (range 9-35% and 20-50%, respectively) in a contact-dependent manner and significantly higher as compared to resting NK cells. Improved killing of these pancreatic cell lines is, at least partly, dependent on IL-15 induced upregulation of TIM-3 and NKG2D. Furthermore, we confirm significant killing of primary PSC by IL-15 activated NK cells in an ex vivo autologous system. Screening for potential targets for immunotherapeutic strategies, we demonstrate surface expression of both inhibitory (PD-L1, PD-L2) and activating (MICA/B, ULBPs and Galectin-9) ligands on primary PSC. These data underscore the therapeutic potential of IL-15 to promote NK cell-mediated cytotoxicity as a treatment of pancreatic cancer and provide promising future targets to tackle remaining PSC.