Abstract 3179: Enhanced pancreatic tumor progression in p48Cre-KrasG12D mice is regulated by natural killer T (NKT) cells dependent on mPGES-1 in tumor-associated macrophages

Abstract Pancreatic cancer (PC) is seldom detected at early stages and most PC tumors are unresectable. The five-year survival rate for PC is <6%. Natural Killer (NK) and Natural Killer T (NKT) cell dysfunction is linked to aggressive tumor growth and poor PC prognosis. NKT cells are known to regulate pro-inflammatory responses of tumor-associated macrophages (TAM). We have shown that pancreatic tumors are high in TAM and overexpress microsomal prostaglandin synthase-1 (mPGES-1). Thus, we performed experiments to clarify the roles of NK, NKT, TAM, and mPGES-1 in K-rasG12D driven pancreatic tumor growth in mice. To understand the regulatory role of NKs, we initially crossed Rag1 mice, which have NK cells and lack T cells, with Kras (p48Cre/+-LSL-KrasG12D/+) mice to generate Rag1-Kras mice. At seven months of age, the Rag1-Kras mice showed reduced pancreatic intraepithelial neoplasia (PanIN) lesions without evidence of carcinoma compared with Kras mice (p<0.0001) which displayed high PanINs (p<0.001) and invasive carcinoma. Flow cytometry (FC) analysis of pancreatic tumors (PTs) showed 75% NK cells (NKp46and NK1.1-positive) in PTs of Rag1-Kras mice compared with 6.7% NK cells in PTs from K-ras mice. These results suggest an inhibitory role of NKs on PT. To further study the role of NKTs, we crossbred CD1d−/− mice with K-ras mice, and generated CD1d−/−-Kras mice deficient in both iNKT and vNKT cells. At 5 months of age, the PTs were analyzed histologically, PTs and spleens were analyzed by FC for macrophages (CD68, stabilin) and mPGES-1 expressions, along with stem-like cells (Epcam-, Dclk1-, and Lgr5- positive cells). CD1d−/−-Kras mice were observed to have significantly increased PT weights, and a 50% increase in total PanINs compared with Kras mice (PanIN1, 175 Vs 362, p<0.0001; PanIN2, 80 Vs 162, p<0.0003; PanIN 3, 17 vs 30, p<0.008). PTs and spleens from CD1d−/−-Kras mice showed significantly increased mPGES-1 expression in M2 type macrophages (p<0.005) compared with Kras mice. Tumors from CD1d−/−-Kras mice had more cancer stem-like cells that were positive for Epcam, Dclk-1, and Lgr5 (25%, p<0.02) compared with tumors from Kras mice. To further confirm the relationship between NKT cells, M2-derived mPGES-1, and PC development, we treated CD1d−/−-Kras mice with mPGES-1-specific inhibitor YS-121 after PanIN lesions formed at 12 weeks of age. Mice were killed after 22 weeks of age. We analyzed PanIN formation and PC. Inhibition of mPGES-1 led to a decrease in PanINs and PC development. Thus, the absence or functional loss of NKT cells leads to increased TAMs (M2) with high mPGES-1, resulting in enhanced pancreatic tumor growth and invasion. These results suggest that NKT cells play a regulatory role on macrophages during Kras-induced pancreatic tumor progression. {Supported in part by Kerley-Cade Chair Endowment and NCI-CN-53300}. Citation Format: Naveena B. Janakiram, Altaf Mohammed, Taylor Bryant, Rebekah Ritchie, Gopal Pathuri, Stan Lightfoot, Mark L. Lang, Chinthalapally V. Rao. Enhanced pancreatic tumor progression in p48Cre-KrasG12D mice is regulated by natural killer T (NKT) cells dependent on mPGES-1 in tumor-associated macrophages. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3179. doi:10.1158/1538-7445.AM2015-3179