Pancreatic ductal adenocarcinoma (PDAC) still ranking 4th in the order of fatal tumor diseases is characterized by a profound tumor stroma with high numbers of tumor-associated macrophages (TAMs). Driven by environmental factors, monocytes differentiate into M1-or M2-macrophages, the latter commonly regarded as being protumorigenic. Because a detailed analysis of TAMs in human PDAC development is still lacking, freshly isolated PDAC-derived TAMs were analyzed for their phenotype and impact on epithelial-mesenchymal-transition (EMT) of benign (H6c7) and malignant (Colo357) pancreatic ductal epithelial cells. TAMs exhibited characteristics of M1-macrophages (expression of HLA-DR, IL-1b, or TNF-a) and M2-macrophages (expression of CD163 and IL-10). In the presence of TAMs, H6c7, and Colo357 cells showed an elongated cell shape along with an increased expression of mesenchymal markers such as vimentin and reduced expression of epithelial E-cadherin. Similar to TAMs, in vitro generated M1-and M2-macrophages both mediated EMT in H6c7 and Colo357 cells. M1-macrophages acquired M2-characteristics during coculture that could be prevented by GM-CSF treatment. However, M1-macrophages still potently induced EMT in H6c7 and Colo357 cells although lacking M2-characteristics. Overall, these data demonstrate that TAMs exhibit anti-as well as proinflammatory properties that equally contribute to EMT induction in PDAC initiation and development.Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor, still with a dismal prognosis. In Western countries, PDAC ranks 4th in the order of death related tumor diseases with a still increasing prevalence.1 Commonly, PDAC is detected in an advanced stage when the tumor has already metastasized so that therapeutic options are very limited, in line with low overall 5-year survival rates of <5%. 2One hallmark of PDAC which is supposed to originate from the ductal epithelium is the pronounced tumor stroma. This marked stromal enrichment is already present in

Evidence accumulates that the transcription factor nuclear factor E2-related factor 2 (Nrf2) has an essential role in cancer development and chemoresistance, thus pointing to its potential as an anticancer target and undermining its suitability in chemoprevention. Through the induction of cytoprotective and proteasomal genes, Nrf2 confers apoptosis protection in tumor cells, and inhibiting Nrf2 would therefore be an efficient strategy in anticancer therapy. In the present study, pancreatic carcinoma cell lines (Panc1, Colo357 and MiaPaca2) and H6c7 pancreatic duct cells were analyzed for the Nrf2-inhibitory effect of the coffee alkaloid trigonelline (trig), as well as for its impact on Nrf2-dependent proteasome activity and resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and anticancer drug-induced apoptosis. Chemoresistant Panc1 and Colo357 cells exhibit high constitutive Nrf2 activity, whereas chemosensitive MiaPaca2 and H6c7 cells display little basal but strong tert-butylhydroquinone (tBHQ)-inducible Nrf2 activity and drug resistance. Trig efficiently decreased basal and tBHQ-induced Nrf2 activity in all cell lines, an effect relying on a reduced nuclear accumulation of the Nrf2 protein. Along with Nrf2 inhibition, trig blocked the Nrf2-dependent expression of proteasomal genes (for example, s5a/psmd4 and α5/psma5) and reduced proteasome activity in all cell lines tested. These blocking effects were absent after treatment with Nrf2 siRNA, a condition in which proteasomal gene expression and proteasome activity were already decreased, whereas siRNA against the related transcription factor Nrf1 did not affect proteasome activity and the inhibitory effect of trig. Depending on both Nrf2 and proteasomal gene expression, the sensitivity of all cell lines to anticancer drugs and TRAIL-induced apoptosis was enhanced by trig. Moreover, greater antitumor responses toward anticancer drug treatment were observed in tumor-bearing mice when receiving trig. In conclusion, representing an efficient Nrf2 inhibitor capable of blocking Nrf2-dependent proteasome activity and thereby apoptosis protection in pancreatic cancer cells, trig might be beneficial in improving anticancer therapy.

Recent advances in tumor biology have revealed that a detailed analysis of the complex interactions of tumor cells with their adjacent microenvironment (tumor stroma) is mandatory in order to understand the various mechanisms involved in tumor growth and the development of metastasis. The mutual interactions between tumor cells and cellular and non-cellular components (extracellular matrix = ECM) of the tumor microenvironment will eventually lead to a loss of tissue homeostasis and promote tumor development and progression. Thus, interactions of genetically altered tumor cells and the ECM on the one hand and reactive non-neoplastic cells on the other hand essentially control most aspects of tumorigenesis such as epithelial-mesenchymal-transition (EMT), migration, invasion (i.e. migration through connective tissue), metastasis formation, neovascularisation, apoptosis and chemotherapeutic drug resistance. In this mini-review we will focus on these issues that were recently raised by two review articles in CCS.

The ability of human gd T cells from healthy donors to kill pancreatic ductal adenocarcinoma (PDAC) in vitro and in vivo in immunocompromised mice requires the addition of gd T-cell-stimulating antigens. In this study, we demonstrate that gd T cells isolated from patients with PDAC tumor infiltrates lyse pancreatic tumor cells after selective stimulation with phosphorylated antigens. We determined the absolute numbers of gd T-cell subsets in patient whole blood and applied a real-time cell analyzer to measure their cytotoxic effector function over prolonged time periods. Because phosphorylated antigens did not optimally enhance gd T-cell cytotoxicity, we designed bispecific antibodies that bind CD3 or Vg9 on gd T cells and Her2/neu (ERBB2) expressed by pancreatic tumor cells. Both antibodies enhanced gd T-cell cytotoxicity with the Her2/Vg9 antibody also selectively enhancing release of granzyme B and perforin. Supporting these observations, adoptive transfer of gd T cells with the Her2/Vg9 antibody reduced growth of pancreatic tumors grafted into SCID-Beige immunocompromised mice. Taken together, our results show how bispecific antibodies that selectively recruit gd T cells to tumor antigens expressed by cancer cells illustrate the tractable use of endogenous gd T cells for immunotherapy.

Transforming growth factor (TGF)-β1 promotes progression of pancreatic ductal adenocarcinoma (PDAC) by enhancing epithelial-mesenchymal transition, cell migration/invasion, and metastasis, in part by cooperating with the small GTPase Rac1. Prompted by the observation of higher expression of Rac1b, an alternatively spliced Rac1 isoform, in pancreatic ductal epithelial cells and in patients with chronic pancreatitis vs. PDAC, as well as in long-time vs. short-time survivors among PDAC patients, we asked whether Rac1b might negatively affect TGF-β1 prometastatic function. Interestingly, the non-malignant pancreatic ductal epithelial cell line H6c7 exhibited a higher ratio of active Rac1b to total Rac1b than the TGF-β1-responsive PDAC cell lines Panc-1 and Colo357. Notably, siRNA-mediated silencing of Rac1b increased TGF-β1/Smad-dependent migratory activities in H6c7, Colo357, and Panc-1 cells, while ectopic overexpression of Rac1b in Panc-1 cells attenuated TGF-β1-induced cell motility. Depletion of Rac1b in Panc-1 cells enhanced TGF-β1/Smad-dependent expression of promoter-reporter genes and of the endogenous Slug gene. Moreover, Rac1b depletion resulted in a higher and more sustained C-terminal phosphorylation of Smad3 and Smad2, suggesting that Rac1b is involved in Smad2/3 dephosphorylation/inactivation. Since pharmacologic or siRNA-mediated inhibition of Smad3 but not Smad2 was able to alleviate the Rac1b siRNA effect on TGF-β1-induced cell migration, our results suggests that Rac1b inhibits TGF-β1-induced cell motility in pancreatic ductal epithelial cells by blocking the function of Smad3. Moreover, Rac1b may act as an endogenous inhibitor of Rac1 in TGF-β1-mediated migration and possibly metastasis. Hence, it could be exploited for diagnostic/prognostic purposes or even therapeutically in late-stage PDAC as an antimetastatic agent.