Abstract 2106: Regulation of Rb1 and caspase 3/7 by miR-17-5p, miR-132/-212, and miR-337-3p: Oncogenic role of miRNAs in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) continues to be one of the most lethal forms of cancer. Reasons for the high mortality associated with this disease include a lack of effective treatments and poor early detection methods. Enhanced understanding of the pathways that are deregulated in PDAC could lead to improved therapies and diagnostics. We and others have reported a microRNA expression signature that is associated with PDAC. The purpose of this study was to identify target genes and pathways that are regulated by miRNAs with altered expression in PDAC. We found several miRNAs including miR-17-5p, −132/-212, and −337-3p that have increased expression in clinical specimens of PDAC compared to normal and adjacent benign pancreas. miR-132 and −212 are located within 472 bp of each other on chromosome 17, have the identical seed sequence and should therefore regulate the identical targets. Through a luciferase reporter assay and western blotting, we found that miR-132/-212 directly regulate the expression of the tumor suppressor Rb1 in the pancreatic tumor cell lines HS766T and PANC-1. Over expression of these miRNAs (miR-132/-212) either through stable expression or pre-miR oligos increased the proliferation rate of HS766T and PANC-1 cells. Expression of 18 genes that are transcriptionally regulated by the E2F including Cyclin A, Cyclin B, PCNA, MCM2, MKI67 and others was increased following miR-132/-212 over expression. Additional genes that are predicted to be targeted by these miRNAs include procaspase 3 (miR-337-3P) and procaspase 7 (miR-132/-212 and miR-17-5p). These caspases are essential in executing programmed cell death in tumors. Western blotting and luciferase reporter assays determined that procaspase 3 and procaspase 7 are regulated by miR-337-3P and miR-132/-212 & miR-17-5p, respectively. Our data strongly suggest that over expression of miR-132/-212 contributes to the enhanced proliferation that is observed in pancreatic cancer. Furthermore, this study is the first to discover that main effector caspases, caspase 3 and 7, are post-transcriptionally regulated by miRNAs. Our findings suggest that resistance to chemotherapeutics in pancreatic tumor tissues may be linked to reduced expression of these procaspases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2106.