Abstract 447: Tumor microenvironment in pancreatic cancer (PDAC): interplay between tumor cells, stromal cells and immune cells
Authors: Karamitopoulou Eva , Wartenberg Martin , Galván José A. , Zlobec Inti , Lugli Alessandro , Perren Aurel 
Published: August 2015

Abstract
Introduction: Tumor budding is considered to be the morphologic correlate of epithelial-mesenchymal-transition (EMT) and is an independent prognostic factor in pancreatic ductal adenocarcinoma (PDAC). Here we explore the interactions between tumor budding cells, stromal cells and immune cells in the microenvironment of the tumor buds in PDAC.
Methods: Multi-punch tissue-microarrays (TMAs) containing punches from the tumor center and the tumor front, including tumor buds, from a well characterized cohort of 120 PDAC patients, were stained immunohistochemically and by mRNA-in-situ-Hybridization (mRNA-ISH)for the EMT markers E-cadherin, β-catenin, Snail, ZEB1, ZEB2, N-cadherin and Twist and for the immune cell markers CD8, CD4, Foxp3, M1- and M2-macrophages. Expression in budding- and stromal cells and immune-cell counts in the microenvironment of the tumor buds were compared with findings in the main tumor.
Results: Tumor buds showed loss of E-cadherin and b-catenin and overexpressed ZEB1 and ZEB2 compared with the neoplastic cells of the main tumor both at protein and mRNA level (p&lt;0.0001 respectively). Stromal cells surrounding tumor buds showed increased protein and mRNA levels of the transcription factors Snail, ZEB1 and ZEB2. The immune microenvironment of the tumor buds composed of numerous Foxp3+cells and M1-macrophages while M2-macrophages were significantly reduced and CD8+cells were almost absent, in contrast to the main tumor.
Conclusions: Tumor budding cells show a shift towards EMT-promoting profiles at protein and mRNA level, compared with the neoplastic cells of the main tumor. Stromal cells surrounding tumor buds express high levels of Snail, ZEB1 and ZEB2 suggesting that some stromal cells may represent complete mesenchymally transformed tumor cells or alternatively that there is a special phenotype of cancer associated fibroblasts supporting EMT-Type tumor-budding through cellular crosstalk in the tumor microenvironment of PDAC. Moreover, there is a tumor favoring immune cell composition in the immediate microenvironment of the tumor buds. Our findings suggest a close interaction of the stromal and immune response with the EMT process in PDAC. The combined assessment of host-associated factors such as stromal and immune response and tumor-associated factors such as EMT-type tumor-budding could help us to achieve superior prognostication and patient stratification than either factor alone.
Citation Format: Eva Karamitopoulou, Martin Wartenberg, José A. Galván, Inti Zlobec, Alessandro Lugli, Aurel Perren. Tumor microenvironment in pancreatic cancer (PDAC): interplay between tumor cells, stromal cells and immune cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 447. doi:10.1158/1538-7445.AM2015-447