Abstract 480: Novel miRNA regulation in an early progression model of PDA
Authors: Chu Nina J. , Armstrong Todd D. , Jaffee Elizabeth M. 
Published: July 2017

The success of immunotherapy is dependent on infiltration and function of T cells within the tumor microenvironment. However, for many cancers, inflammatory and stromal cells provide formidable barriers to T cell access. Emerging data suggests that the cellular barriers to T cell access and function are regulated by both genetic and epigenetic factors. Identification of these regulators should provide new targets for enhancing immunotherapy.

The overall goal of this research is to construct a comprehensive profile of miRNA expression within the inflammatory and stromal cells that develop in the earliest pre-malignant pancreatic intraepithelial neoplasias (PanINs) in the KrasG12D/+;Trp53R172H/+;Pdx-1-Cre (KPC) mouse model, a spontaneous model of pancreatic ductal adenocarcinomas (PDA) tumorigenesis. Specifially, we aim to investigate the functional roles of key differentially expressed miRNAs in propagating the tumor microenvironment via modulating the signaling between transformed ductal epithelial cells and the recruited cancer associated fibroblasts (CAFs) that comprise the majority of the desmoplastic stroma that characterizes PDA. Although numerous studies have described molecular alterations that are involved in pancreatic cancer development and progression, little is known about the miRNA regulatory profile and the associated inflammatory changes within the tumor microenvironment in the earliest PanIN lesions.

We conducted miRNA microarray analysis to determine the levels of 750 unique miRNAs in the pancreata of KPC mice ranging from 4 to 12 weeks of age (pre-PanIN1 to PDA). miRNA was isolated from normal pancreatic ducts, PanIN grades 1 through 3, and PDA via laser capture microdissection. miRNA expression was quantified by Taqman miRNA OpenArrays and confirmed by qPCR analysis. Out of the 750 rodent miRNAs, 4 miRNAs (miR-21, miR-16, miR-19b, and miR-224) were significantly upregulated throughout PDA development. miR-21 and miR-224 are of particular interest for their regulation of targets in cancer promoting inflammatory pathways and epithelial-mesenchymal transition (EMT).

To investigate the roles that miR-21 and miR-224 play in the developing microenvironment, primary KPC pancreatic ductal epithelial and fibroblast cell lines were established via fluorescence activated cell sorting (FACS) in order to perform in vitro miRNA knock-in and knock-out studies. Additionally, miRNA fluorescence in situ hybridization (miR-FISH) was performed to examine the spatial expression of miR-21 throughout progression of the early microenvironment. miR-21 is expressed at low levels in wildtype pancreata, but is highly expressed particularly in ductal epithelial cells of late stage KPC pancreata. Additional studies are underway to determine the functional role of this miRNA in PDA development and progression.

Citation Format: Nina J. Chu, Todd D. Armstrong, Elizabeth M. Jaffee. Novel miRNA regulation in an early progression model of PDA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 480. doi:10.1158/1538-7445.AM2017-480