Abstract B01: Ets-2 acts as a novel oncogene in cancer associated fibroblasts and promotes pancreatic tumor initiation and development
Authors: Pitarresi Jason R. , Wu Jinghai , Woelke Sarah , Kladney Raleigh , Cuitino Maria , Yu Lianbo , Michael Ostrowski C. 
Published: October 2015

Purpose of Study:Pancreatic cancer remains an overwhelmingly fatal disease with approximately 95% of patients dying within 5 years of diagnosis. Many recent reports have highlighted the emerging role that stromal cells’fibroblasts in particular’have on pancreatic tumor cell biology. It has become apparent that new models of pancreatic cancer that accurately portray the tumor microenvironment (TME) are necessary to move the field forward. Advances in genetic tools to modulate the TME developed in our lab have allowed us the unique opportunity to manipulate specific stromal cell compartments. Our overarching hypothesis is: Ets-2 in the pancreatic tumor-associated stroma promotes tumor initiation and development by regulating essential signaling pathways in fibroblasts and is critical for tumor-stroma co-evolution.

Research Method: In this study we use a previously validated and well-studied genetically engineered mouse model of pancreatic cancer that relies on constitutive activation of the Kras oncogene tumor cell lineage. We simultaneously employ lox-cre technology to conditionally delete our gene of interest exclusively in the fibroblast compartment of the pancreas. For this study we delete the transcription factor Ets-2, which has previously been shown to effect tumor initiation and growth in mammary stroma.

Novel Findings: Here we show that Ets-2 in pancreatic tumor-associated stroma promotes tumor formation by regulating essential signaling pathways in stromal fibroblasts and is critical for tumor-stroma co-evolution. We conditionally deleted Ets-2 in cancer associated fibroblasts (CAFs), thus altering stroma-tumor crosstalk and resulting in delayed tumor initiation. Specifically, we saw a decrease in pre-cancerous acinar-to-ductal metaplasic (ADM) and pancreatic intraepithelial neoplastic (PanIN) lesions in mice null for Ets-2 in the fibroblast compartment. In order to investigate the mechanism by which Ets-2 is able to effect progression of tumors from the fibroblast compartment, we developed a method for harvesting and purifying primary pancreatic CAFs. We performed microarray and gene expression analysis on Ets-2 deleted CAFs and saw significantly decreased expression of secreted factors. The altered secretome upon Ets-2 deletion in fibroblasts was crucially lacking tumor necrosis factor alpha (TNFα), a known pro-tumor ligand in pancreatic carcinogenesis. Furthermore, we found evolutionarily conserved Ets-2 transcription factor binding sites in the proximal promoter of TNFα, suggesting that Ets-2 directly regulates TNFα transcription. Thus we have shown that Ets-2 ablation in pancreatic fibroblasts delays pancreatic tumor initiation through the pro-tumor ligand TNFα.

Conclusions and Implications:This report shows that deleting a gene in pancreatic fibroblasts causes a change in tumor-stroma co-evolution and that Ets-2 is able to act as a novel oncogene in cancer associated fibroblasts to promote pancreatic carcinogenesis. We have shown that Ets-2 deletion significantly changed the biological role of the CAFs and negatively effects tumor growth. This finding is relevant to the field of pancreatic cancer because it shows that the pancreatic TME can play a driver role in overall tumor initiation and development. These collective findings contribute to our lab’s overall hypothesis that the tumor microenvironment is not a mere bystander or byproduct of tumor development, but rather that it can drive tumor evolution amongst a variety of cancers.

Citation Format: Jason R. Pitarresi, Jinghai Wu, Sarah Woelke, Raleigh Kladney, Maria Cuitino, Lianbo Yu, Ostrowski C. Michael. Ets-2 acts as a novel oncogene in cancer associated fibroblasts and promotes pancreatic tumor initiation and development. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B01.