In considering an overview of microRNA biology, it is useful to consider microRNAs as a part of cellular communication. At the simplest level, microRNAs act to decrease the expression of mRNAs that contain stretches of sequence complementary to the microRNA. This function can be likened to the function of endogenous or synthetic short interfering RNA (siRNA). However, microRNA function is more complicated and nuanced than this ‘on-off’ model would suggest. Further, many microRNA targets are themselves non-coding RNAs. In this review, we will discuss the role of microRNAs in shaping the proteome of the cell in a way that is consistent with microRNA involvement in a highly regulated conversation, sensitive to outside influence and internal feedback.

Sonic hedgehog (SHH) expression is tightly regulated throughout development. In the adult, aberrant expression of SHH is associated with the onset and progression of pancreatic cancer, as evidenced by increased levels of expression in premalignant and malignant lesions of the pancreas. We investigated the hypothesis that SHH, secreted from pancreatic tumors, functions in a paracrine manner to influence the biological condition of mesenchymal and endothelial cells. Orthotopic implantation of a pancreatic tumor cell line expressing SHH (Capan-2) and a transformed primary cell line that overexpresses SHH (T-HPNE.SHH) were used to show that overexpression of SHH increased primary tumor size and metastasis. Treatment with a neutralizing antibody, 5E1, decreased primary tumor volume and inhibited metastasis. Lyve-1 þ vessels and stromal fibroblasts in tumors expressed primary cilium and showed localization of the receptor Smoothened to the primary cilium, providing evidence of active SHH signaling through this pathway. Although primary cilia are present on normal ductal cells of the pancreas, we did not observe primary cilium on the ductal tumor cells, suggesting decreased autocrine signaling through pathways mediated by the primary cilium in pancreatic cancer. These data support the hypothesis that SHH, secreted from pancreatic epithelia, is critical in establishing and regulating the tumor microenvironment and thereby contributes to progression of pancreatic cancer.

Recent studies have identified a cholestatic variant of nonalcoholic fatty liver disease (NAFLD) with portal inflammation and ductular reaction. Based on reports of biliary damage, as well as increased circulating free fatty acids (FFAs) in NAFLD, we hypothesized the involvement of cholangiocyte lipoapoptosis as a mechanism of cellular injury. Here, we demonstrate that the saturated FFAs palmitate and stearate induced robust and rapid cell death in cholangiocytes. Palmitate and stearate induced cholangiocyte lipoapoptosis in a concentration-dependent manner in multiple cholangiocyte-derived cell lines. The mechanism of lipoapoptosis relied on the activation of caspase 3/7 activity. There was also a significant up-regulation of the proapoptotic BH3-containing protein, PUMA. In addition, palmitate-induced cholangiocyte lipoapoptosis involved a time-dependent increase in the nuclear localization of forkhead family of transcription factor 3 (FoxO3). We show evidence for posttranslational modification of FoxO3, including early (6 hours) deacetylation and dephosphorylation that coincide with localization of FoxO3 in the nuclear compartment. By 16 hours, nuclear FoxO3 is both phosphorylated and acetylated. Knockdown studies confirmed that FoxO3 and its downstream target, PUMA, were critical for palmitate- and stearate-induced cholangiocyte lipoapoptosis. Interestingly, cultured cholangiocyte-derived cells did not accumulate appreciable amounts of neutral lipid upon FFA treatment. Conclusion Our data show that the saturated FFAs palmitate and stearate induced cholangiocyte lipoapoptosis by way of caspase activation, nuclear translocation of FoxO3, and increased proapoptotic PUMA expression. These results suggest that cholangiocyte injury may occur through lipoapoptosis in NAFLD and nonalcoholic steatohepatitis patients.

Purpose The presence of TNFα in ~ 50% of surgically resected tumors suggests that the canonical NF-κB and the mTOR pathways are activated. IκB kinase β (IKKβ) acts as the signaling node that regulates transcription via the p-IκBα/NF-κB axis and regulates translation via the mTOR/p-S6K/p-eIF4EBP axis. A kinome screen identified a quinoxaline urea analog 13-197 as an IKKβ inhibitor. We hypothesized that targeting the NF-κB and mTOR pathways with 13-197 will be effective in malignancies driven by these pathways. Experimental Design Retrospective clinical and preclinical studies in pancreas cancers have implicated NF-κB. We examined the effects of 13-197, on the downstream targets of the NF-κB and mTOR pathways in pancreatic cancer cells, pharmacokinetics, toxicity and tumor growth and metastases in vivo. Results 13-197 inhibited the kinase activity of IKKβ in vitro and TNFα mediated NF-κB transcription in cells with low-μM potency. 13-197 inhibited the phosphorylation of IκBα, S6K and eIF4EBP, induced G1 arrest and down regulated the expression of antiapoptotic proteins in pancreatic cancer cells. Prolonged administration of 13-197 did not induce granulocytosis and protected mice from LPS-induced death. Results also show that 13-197 is orally available with extensive distribution to peripheral tissues and inhibited tumor growth and metastasis in an orthotopic pancreatic cancer model without any detectable toxicity. Conclusion These results suggest that 13-197 targets IKKβ and thereby inhibits mTOR and NF-κB pathways. Oral availability along with in vivo efficacy without obvious toxicities makes this quinoxaline urea chemotype, a viable cancer therapeutic.

Pancreatic ductal adenocarcinoma (PDA) is a leading cause of cancer mortality with a dismal 2–5% 5-year survival rate. Monotherapy with Gemcitabine has limited success, highlighting the need for additional therapies that enhance the efficacy of current treatments. We evaluated the combination of Gemcitabine and Rosiglitazone, an FDA-approved drug for the treatment of type II diabetes, in an immunocompetent transplantable mouse model of pancreatic cancer. Tumor progression, survival and metastases were evaluated in immunocompetent mice with subcutaneous or orthotopic pancreatic tumors treated with Pioglitazone, Rosiglitazone, Gemcitabine or combinations of these. We characterized the impact of high dose Rosiglitazone and Gemcitabine therapy on immune suppressive mediators, including MDSC and T regulatory cells, and on modulation of peripheral and intra-tumoral T cell populations. Combinations of Rosiglitazone and Gemcitabine significantly reduced tumor progression and metastases, enhanced apoptosis, and significantly extended overall survival compared to Gemcitabine alone. Rosiglitazone altered tumor-associated immune suppressive mediators by limiting early MDSC accumulation and intra-tumoral T regulatory cells. Combination therapy with Rosiglitazone and Gemcitable modulated T cell populations by enhancing circulating CD8+ T cells and intra-tumoral D4+ and CD8+ T cells while limiting T regulatory cells. The results suggest that Rosiglitazone, in combination with Gemcitabine, decreases immune suppressive mechanisms in immunocompetent animals and provide pre-clinical data in support of combining Rosiglitazone and Gemcitabine as a clinical therapy for pancreatic cancer.

Transmembrane mucins, MUC4 and MUC16 are associated with tumor progression and metastatic potential in human pancreatic adenocarcinoma. We discovered that miR-200c interacts with specific sequences within the coding sequence of MUC4 and MUC16 mRNAs, and evaluated the regulatory nature of this association. Pancreatic cancer cell lines S2.028 and T3M-4 transfected with miR-200c showed a 4.18 and 8.50 fold down regulation of MUC4 mRNA, and 4.68 and 4.82 fold down regulation of MUC16 mRNA compared to mock-transfected cells, respectively. A significant reduction of glycoprotein expression was also observed. These results indicate that miR-200c overexpression regulates MUC4 and MUC16 mucins in pancreatic cancer cells by directly targeting the mRNA coding sequence of each, resulting in reduced levels of MUC4 and MUC16 mRNA and protein. These data suggest that, in addition to regulating proteins that modulate EMT, miR-200c influences expression of cell surface mucins in pancreatic cancer.

Core 3 derived glycans, a major type of O-glycan expressed by normal epithelial cells of the gastrointestinal tract, are downregulated during malignancy, because of loss of expression of functional β3-N-acetylglucosaminyltransferase-6 (core 3 synthase). We investigated the expression of core 3 synthase in normal pancreas and pancreatic cancer and evaluated the biological effects of re-expressing core 3 synthase in pancreatic cancer cells that had lost expression. We determined that pancreatic tumors and tumor cell lines have lost expression of core 3 synthase. We therefore re-expressed in human pancreatic cancer cells (Capan-2 and FG) to investigate the contribution of core 3 glycans to malignant progression. Pancreatic cancer cells expressing core 3 synthase showed reduced in vitro cell proliferation, migration and invasion compared with vector control cells. Expression of core 3 O-glycans induced altered expression of β1 integrin, decreased activation of focal adhesion kinase, led to the down regulation of expression of several genes including REG1α and FGFR3, and altered lamellipodia formation. The addition of a GlcNAc residue by core 3 synthase leads to the extension of the tumor associated Tn structure on MUC1. Orthotopic injection of FG cells expressing core 3 synthase into the pancreas of nude mice produced significantly smaller tumors and decreased metastasis to the surrounding tissues compared to vector control FG cells. These findings indicate that expression of core 3 derived O-glycans in pancreatic cancer cells suppresses tumor growth and metastasis through modulation of glycosylation of mucins and other cell surface and extracellular matrix proteins.

We describe the pathology of early pancreatic cancer and present an overview of known molecular alterations that occur in these lesions. There are three defined precursor lesions in current models of pancreatic cancer: pancreatic intraepithelial neoplasia (PanIN), mucinous cystic neoplasms (MCN), and intraductal papillary mucinous neoplasms (IPMN). Molecular alterations detected in these lesions include: telomeres, K-ras and downstream targets, p16/CDKN2A, p53, SMAD4/DPC4, microRNAs, mucins and their post-translational processing, inflammatory cytokines, CEACAM, and epigenetic alterations. We summarize previous analyses of these markers as diagnostic markers of disease, and suggest areas of future study.