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Pancreatic ductal adenocarcinoma (PDAC) is often diagnosed when liver metastases already emerged. This study elucidated the impact of hepatic stromal cells on growth behavior of premalignant and malignant pancreatic ductal epithelial cells (PDECs). Liver sections of tumor-bearing KPC mice comprised micrometastases displaying low proliferation located in an unobtrusive hepatic microenvironment whereas macrometastases containing more proliferating cells were surrounded by hepatic myofibroblasts (HMFs). In an age-related syngeneic PDAC mouse model livers with signs of age-related inflammation exhibited significantly more proliferating disseminated tumor cells (DTCs) and micrometastases despite comparable primary tumor growth and DTC numbers. Hepatic stellate cells (HSC), representing a physiologic liver stroma, promoted an IL-8 mediated quiescence-associated phenotype (QAP) of PDECs in coculture. QAP included flattened cell morphology, Ki67-negativity and reduced proliferation, elevated senescence-associated β galactosidase activity and diminished p-Erk/p-p38-ratio. In contrast, proliferation of PDECs was enhanced by VEGF in the presence of HMF. Switching the micromilieu from HSC to HMF or blocking VEGF reversed QAP in PDECs. This study demonstrates how HSCs induce and maintain a reversible QAP in disseminated PDAC cells, while inflammatory HMFs foster QAP reversal and metastatic outgrowth. Overall, the importance of the hepatic microenvironment in induction and reversal of dormancy during PDAC metastasis is emphasized. [ABSTRACT FROM PUBLISHER]

Chronic pancreatitis (CP) is a risk factor of pancreatic ductal adenocarcinoma (PDAC) and characterized by a pronounced desmoplastic reaction with CD4+T cells accounting for the majority of the stromal T cell infiltrate. Epithelial-mesenchymal-transition (EMT) is a critical process for metastasis by which epithelial/carcinoma cells become enabled to disseminate probably prior to tumor formation. To investigate whether CD4+T cells induce EMT in human pancreatic ductal epithelial cells, premalignant H6c7 cells were mono- or co-cultured with human CD4+CD25+CD127−CD49d−regulatory T cells (T-regs) or CD4+CD25−T-effector cells (T-effs) being isolated by negative magnetic bead separation from blood of healthy donors. Particularly in the presence of activated T-effs, H6c7 cells acquired a spindle-shaped morphology, reduced E-cadherin expression, and elevated expression of the mesenchymal proteins vimentin, L1CAM, and ZEB-1. This was accompanied by an increased invasive behavior. Moreover, activated T-effs exerted similar effects in the PDAC cell line T3M4. Blocking of TNF-α and IL-6 being released at greater amounts into supernatants during co-cultures with activated T-effs attenuated the EMT-associated alterations in H6c7 cells. Supporting these findings, EMT-associated alterations (exemplified by reduced E-cadherin expression and enhanced expression of vimentin and L1CAM) were predominantly detected in ductal epithelium of CP tissues surrounded by a dense stroma enriched with CD4+T cells. Overall this study points to a novel role of CD4+T cells beyond their immune function in pancreatic tumorigenesis and underscores the view that EMT induction in pancreatic ductal epithelial cells represents an early event in PDAC development being essentially promoted by inflammatory processes. [ABSTRACT FROM PUBLISHER]

Chronic pancreatitis (CP) is a risk factor of pancreatic ductal adenocarcinoma (PDAC) and characterized by a pronounced desmoplastic reaction with CD4 + T cells accounting for the majority of the stromal T cell infiltrate. Epithelial-mesenchymal-transition (EMT) is a critical process for metastasis by which epithelial/carcinoma cells become enabled to disseminate probably prior to tumor formation. To investigate whether CD4 + T cells induce EMT in human pancreatic ductal epithelial cells, premalignant H6c7 cells were mono- or co-cultured with human CD4 + CD25 + CD127 - CD49d - regulatory T cells (T-regs) or CD4 + CD25 - T-effector cells (T-effs) being isolated by negative magnetic bead separation from blood of healthy donors. Particularly in the presence of activated T-effs, H6c7 cells acquired a spindle-shaped morphology, reduced E-cadherin expression, and elevated expression of the mesenchymal proteins vimentin, L1CAM, and ZEB-1. This was accompanied by an increased invasive behavior. Moreover, activated T-effs exerted similar effects in the PDAC cell line T3M4. Blocking of TNF-α and IL-6 being released at greater amounts into supernatants during co-cultures with activated T-effs attenuated the EMT-associated alterations in H6c7 cells. Supporting these findings, EMT-associated alterations (exemplified by reduced E-cadherin expression and enhanced expression of vimentin and L1CAM) were predominantly detected in ductal epithelium of CP tissues surrounded by a dense stroma enriched with CD4 + T cells. Overall this study points to a novel role of CD4 + T cells beyond their immune function in pancreatic tumorigenesis and underscores the view that EMT induction in pancreatic ductal epithelial cells represents an early event in PDAC development being essentially promoted by inflammatory processes.