Abstract 514: A novel dual color mouse model for studying the tumor microenvironment of pancreatic adenocarcinoma

Abstract

Abstract We have developed a novel, dual color, immunocompetent mouse model for studying the pancreatic tumor microenvironment using fluorescence imaging. To develop this model, we used mice engineered to constitutively express a conditional tdTomato fluorescent transgene that converts to the expression of EGFP following Cre recombinase-mediated intramolecular rearrangement of the transgene. The reporter transgene is driven by a strong, ubiquitous promoter from a well-characterized genomic locus. Both tdTomato and EGFP fluorescent proteins are membrane-targeted, allowing distinction of single cells and cell processes within the microenvironmental setting. For our studies of the pancreatic microenvironment, we used PdxCre (Pdx-1-Cre) transgenic mice. PdxCre mice express Cre recombinase within the developing pancreas during embryogenesis. To generate mice in which the pancreatic parenchyma, expressing membrane-targeted green fluorescence (mG), is highlighted against the red fluorescent (mT) backlight of stromal and non-pancreatic tissues, we crossed PdxCre transgenic mice with conditional fluorescent (mTmG) indicator mice. Both lines are on a mixed C57Bl/6 × Sv129 background, backcrossed several generations onto C57Bl/6. We used PDA4964 pancreatic adenocarcinoma cells, derived from genetically engineered triple transgenic (LSL-KrasG12D/+;LSL-Trp53R172H/+; PdxCre) mutant mice, to generate orthotopic tumors in the pancreata of PdxCre+, mTmG+ dual transgenic, dual color mice. Using a dosage of 1 × 106 tumor cells per mouse, half of the mice developed tumors within 4-6 weeks. Ex vivo imaging of orthotopic tumor-bearing mice at necropsy revealed large pancreatic tumors comprised of non-fluorescent tumor cells supported and nourished by red fluorescent host stromal and vascular cells. The expanding tumor masses distorted and displaced the adjacent green fluorescent host pancreatic parenchyma. Upon microscopic examination of the tumor-host interface, cell borders of individual host pancreatic parenchymal and stromal cells were clearly outlined. Our preliminary findings indicate that this novel, dual color, immunocompetent mouse model will be valuable for studying the pancreatic tumor microenvironment using fluorescence imaging. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 514. doi:10.1158/1538-7445.AM2011-514