Abstract 5255: Lack of chemopreventive effects of dietary P2×7R inhibitors against pancreatic cancer in p48Cre/+-LSL-KrasG12D/+ mice
Authors: Mohammed Altaf , Janakiram Naveena B. , Madka Venkateshwar , Pathuri Gopal , Li Qian , Ritchie Rebekah , Biddick Laura , Kutsche Hannah , Zhang Yuting , Singh Anil , Gali Hariprasad , Lightfoot Stan , Steele Vernon E. , Suen Chen S. , Rao Chinthalapally V. 
Published: July 2016

Abstract
Pancreatic cancer (PC) still remains a devastating disease that is almost uniformly lethal. Despite advances in the field of molecular genetics in human pancreatic cancers, targeted therapies has not yet translated to an improved overall survival for patients. Chronic inflammation is hallmark of many cancers, including PC. P2×7R is the most potent of the membrane receptors responsible for inflammasome activation and release of inflammatory cytokines. Sustained stimulation of P2×7R drives induction of NLRP inflammasome activation. To understand the role of P2×7 receptor and inflammasome in pancreatic tumor progression, we carried transcriptomic analysis of LSL-Kras pancreatic tumors by next generation sequencing. Results showed that the P2×7 receptor (∼20-fold); key inflammasome components, IL-1β (∼45-fold), caspase-1 (15-fold), IL-18 (∼35-fold), IL-33 (∼93 folds), TNF-α (∼13-fold) and COX-2 (∼41-fold) are highly expressed (p&lt;0.05). Analysis of human PC cell lines, human and mouse PC tissues by western immunoblotting, real time (RT)-polymerase chain reaction (PCR), immunohistochemistry and/or immunofluorescence suggest that the P2×7R is a critical contributor to the progression of pancreatic tumor growth. Hence, to target P2×7R, we tested the effects of two P2×7R antagonists A438079 and AZ10606120 at two doses (50 and 100 ppm) on pancreatic intraepithelial neoplasms (PanINs) and their progression to PDAC in p48Cre/+-LSL-KrasG12D/+ mice. Six-week old KrasG12D/+ (24-36/group) mice were fed (AIN-76A) diets containing 0, 50 or 100 ppm of A438079 and AZ10606120 for 38 weeks. Pancreata were collected, weighed, and evaluated histopathologically for PanINs and PDAC. To understand molecular mechanisms, we analyzed levels of proliferation, inflammatory and cell cycle makers; PCNA, p21, P2×7R, NLRP, COX-2, IL-33, caspase-3, caspase-1, Cdc25c and p53 expressions by IHC, IHF, Western blotting, and/or RT-PCR methods. Results suggest that control diet fed mice showed 50% incidence of PDAC in male mice. Dietary A4338079 and AZ10606120 showed up to 60% incidence of PDAC. CT-PET imaging analysis showed enhanced tumor growth in treatment groups. Importantly, the carcinoma spread in untreated mice was 24% as compared to 43-53% in treatment groups. Also, marginal increase of PanIN 3 (carcinoma in-situ) was observed in drug treated mice. Both drugs showed a decrease in caspase-3, caspase-1, p21 and Cdc25c. Dietary A438079 showed modest inhibition of PCNA, P2×7R, NLRP, and IL-33 whereas AZ10606120 had no effects. In summary, targeting the P2×7R pathway by A438079 and AZ10606120 failed to show significant chemopreventive effects in suppression of PC and hence caution is needed while treating high risk individuals for PC with P2×7R inhibitors. Also, it is not clear whether dietary route of administration might be reason for lack of efficacy. {Supported by NCI-CN-N01- 25008-78}.
Citation Format: Altaf Mohammed, Naveena B. Janakiram, Venkateshwar Madka, Gopal Pathuri, Qian Li, Rebekah Ritchie, Laura Biddick, Hannah Kutsche, Yuting Zhang, Anil Singh, Hariprasad Gali, Stan Lightfoot, Vernon E. Steele, Chen S. Suen, Chinthalapally V. Rao. Lack of chemopreventive effects of dietary P2×7R inhibitors against pancreatic cancer in p48Cre/+-LSL-KrasG12D/+ mice. [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 5255.