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Pancreatic cancer (PC) is an aggressive malady with proclivity for early metastasis. Overexpression of toll-like receptor 4 (TLR4) in pancreatic ductal adenocarcinoma, the most common type of pancreatic malignancy, correlates to tumor size, lymph node involvement, venous invasion and pathological stage. Lipopolysaccharides (LPS) are natural TLR4 ligands that have been shown to increase the invasive ability of PC cells. However, rapid inactivation of circulating LPS and low systemic absorption of inhaled LPS from the bronchoalveolar compartment make other agonists such as saturated fatty acids more suitable to be considered for TLR4-related cell invasiveness. Interestingly, PC risk was strongly associated to intake of saturated fat from animal food sources, in particular to consumption of saturated palmitic acid (PA). In the present study, we investigated the influence of PA on the invasive capacity of human PC cells AsPC-1. Using specific inhibitors, we found that PA stimulation of these tumor cells induced a TLR4-mediated cell invasion. Our results also indicate that the signaling events downstream of TLR4 involved generation of reactive oxygen species, activation of nuclear factor-kappa beta, and secretion and activation of matrix metalloproteinase 9 (MMP-9). Furthermore, PA stimulation decreased the levels of the micro RNA 29c (miR-29c). Of note, while inhibition of miR-29c increased MMP-9 mRNA levels, MMP-9 secretion and activation, and invasiveness, miR-29c mimic abrogated all these PA-stimulated effects. These results strongly suggest that miR-29c could be an attractive potential pharmacological agent for antitumoral therapy in PC. [ABSTRACT FROM AUTHOR]

Abstract: In our previous study, we found that blockade of SDF-1/CXCR4 signaling inhibits pancreatic cancer cell migration and invasion in vitro. However, the mechanism governing the downstream regulation of SDF-1/CXCR4-mediated invasion remains unclear. Here we report the role of SDF-1/CXCR4 in pancreatic cancer and the possible mechanism of SDF-1/CXCR4-mediated pancreatic cancer invasion. We show that there is a cross-talk between SDF-1/CXCR4 axis and non-canonical Hedgehog (Hh) pathway in pancreatic cancer. Furthermore, our data demonstrate that the ligand of CXCR4, SDF-1 induces CXCR4-positive pancreatic cancer invasion, epithelial–mesenchymal transition (EMT) process and activates the non-canonical Hh pathway. Moreover, we also demonstrate that the invasion of a pancreatic cancer and EMT resulting from the activation of SDF-1/CXCR4 axis is effectively inhibited by Smoothened (SMO) inhibitor cyclopamine and siRNA specific to Gli-1. Collectively, these data demonstrate that SDF-1/CXCR4 modulates the non-canonical Hh pathway by increasing the transcription of SMO in a ligand-independent manner. Taken together, SDF-1/CXCR4 axis may represent a promising therapeutic target to prevent pancreatic cancer progression. [Copyright &y& Elsevier]

Diabetes mellitus and pancreatic cancer are intimately related, as approximately 85% of pancreatic cancer patients suffer from glucose intolerance or even diabetes. In this study, we evaluate the underlying mechanism by which hyperglycemia modulates the invasive potential of cancer cells and contributes to their enhanced metastatic behavior. Here we show that hyperglycemia increases the hydrogen peroxide (H2O2) concentration through up-regulation of manganese superoxide dismutase (SOD2) expression, which further activates the ERK and p38 MAPK pathways, as well as the transcription factors NF-κB and AP-1, in a time-dependent manner. The invasion of pancreatic cancer cells resulting from the activation of the H2O2/MAPK axis under high glucose conditions is effectively inhibited by PD 98059 (ERK inhibitor), SB 203580 (p38 MAPK inhibitor), polyethylene glycol-conjugated catalase (PEG-CAT), or the siRNA specific to SOD2. In addition, streptozotocin-treated diabetic nude mice exhibit a stronger tumor invasive ability in renal capsule xenografts which could be suppressed by PEG-CAT treatment. Furthermore, the integrated optical density (IOD) of SOD2 and uPA stainings is higher in the tumor tissues of pancreatic cancer patients with diabetes compared with pancreatic cancer patients with euglycemia. Taken together, our results demonstrate that hyperglycemia enhances cell invasive ability through the SOD2/H2O2/MAPK axis in human pancreatic cancer. Thus, SOD2/H2O2/MAPK axis may represent a promising therapeutic target for pancreatic cancer patients combined with diabetes mellitus.