(69g) Function and Regulation of Regenerating Proteins in Pancreatic Cells

Regenerating islet proteins (Regs) comprise a family of 16-20 kDa polypeptides which have been implicated in diverse processes including proliferation, differentiation and prevention of apoptosis in normal pancreas development, diabetes, pancreatitis and pancreatic cancer [1]. Patients with pancreatic ductal adenocarcinoma exhibit significantly higher levels of Reg1A than healthy subjects. Yet, the exact mechanisms underlying Reg protein, expression, function and regulation remain unknown. We focused on a particular member of the Reg family, namely Reg1, which is involved in pancreatic tissue development and cancer. To that end, we have been successful in engineering the production of mouse Reg1 and human REG1A proteins in yeast to facilitate our experimentation. Exposure of cultured cells to the recombinant proteins caused the increase in proliferation thereby confirming the Reg1 activity. We also hypothesized that Reg1 targets cyclin D1 which controls cellular growth. Treatment of pancreatic MIN6 beta-cells resulted in increased expression of cyclin D1 as determined by quantitative PCR and a luciferase-based assay using a cyclin D1 promoter construct. The expression of microRNAs (miRNAs) implicated in pancreatic cancer was profiled aiming at discovering regulators of the expression of Regs. This led to the identification of miRNAs, some of which are differentially expressed in pancreatic acinar and islet cells as well as in pancreatic adenocarcinoma cell lines. In silico identification of miRNAs targeting Reg1 were combined with experiments. Following miRNA overexpression in acinar cells, we observed a reduction in mouse Reg1 expression corroborating our findings at the protein level (western blotting). Our findings are a step toward uncovering the function(s) of Reg proteins and the regulation of their expression in the context of normal and pathological states, especially in pancreatic cancer.