Abstract 244: SPINK1 insufficiency induces impaired autophagy resulting in chronic pancreatitis

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Abstract Background& Objective: Several studies reported that chronic pancreatitis is a risk factor for pancreatic ductal adenocarcinoma (PDAC). Serine protease inhibitor Kazal type 1 (SPINK1), also known as pancreatic secretory trypsin inhibitor (PSTI), was originally isolated from the pancreas. In mice, the homologous gene is designated as Spink3. SPINK1/Spink3 covalently can bind to activated trypsin within the pancreatic acinar cells to form an inactive and stable complex and to prevent acute pancreatitis, a major inflammatory disorder of the pancreas. The mutations of SPINK1 gene are associated with various forms of idiopathic pancreatitis. We previously showed that deletion of Spink3 causes pancreatitis-like changes in the mouse. A careful molecular and pathological analysis of this genetically engineered mouse model will reveal the chronic of nflammation in the pancreas. The aim of this study was to rescue the Spink3-/- phenotype by generating Spink3-/- mice with knocked-in SPINK1, and to analyze molecular mechanisms that initiate pancreatitis or drive its progression from acute to chronic disease in this genetic model. Methods: We placed SPINK1 minigene (KI) into mouse Spink3 locus, using the Cre-loxP technology and generated chimeric mice (Spink3KI/+). Spink3KI/+ mice were crossed to Spink3+/- mice, thus generating Spink3KI/-. Mice were followed up to 8 weeks old. Time-dependent changes in pancreatic histology, stellate cell ctivation, and serum amylase were measured. Results: Spink3KI/KI mice showed no abnormalities in pancreas or any other organ during the 8 weeks age of observation, indicating that human SPINK1 can rescue Spink3 deficiency in physiological condition. Spink3KI/- mice showed slight growth etardation. The pancreas of Spink3KI/- mice at birth contained normal acinar cells. The Spink3KI/- mice time-dependently developed pathologic features of chronic tissue damage, including loss of acinar cells, intralobular fibrosis with activated pancreatic stellate cells. Interlobular ducts were dilated and contained protein plugs, which resembled chronic pancreatitis in human. In the pancreas of Spink3KI/- mice, we found that trypsin activity increased, and large vacuoles, derived from autophagy, appeared in acinar cells. p62, which is a selective substrate for autophagy aggregated in acinar cells, suggested that autophagy is impaired in Spink3KI/- acinar cells. Conclusions: We demonstrated that SPINK1 insufficiency caused chronic pancreatitis in vivo. Impaired autophagy and high trypsin activity may contribute to cause chronic pancreatitis in human.We established chronic pancreatitis model in human SPINK1 knockin mice and identified shared pathological alterations in human and mouse chronic pancreatitis.Thus,this mouse model provides a suitable tool to analyze the oncogenesis from chronic pancreatitis. Citation Format: Kazuya Sakata, Masaki Ohmuraya, Katsunobu Taki, Daisuke Hashimoto, Satoshi Ida, Hidetoshi Nitta, Hiromitu Hayashi, Akira Chikamoto, Tooru Beppu, Hideo Baba. SPINK1 insufficiency induces impaired autophagy resulting in chronic pancreatitis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 244. doi:10.1158/1538-7445.AM2014-244