The majority of human pancreatic cancers have activating mutations in the KRAS proto-oncogene. These mutations result in increased activity of the NF-κB pathway and the subsequent constitutive production of proinflammatory cytokines. Here, we show that inhibitor of κB kinase 2 (Ikk2), a component of the canonical NF-κB signaling pathway, synergizes with basal Notch signaling to upregulate transcription of primary Notch target genes, resulting in suppression of antiinflammatory protein expression and promotion of pancreatic carcinogenesis in mice. We found that in the Kras G12D Pdx1-cre mouse model of pancreatic cancer, genetic deletion of Ikk2 in initiated pre-malignant epithelial cells substantially delayed pancreatic oncogenesis and resulted in downregulation of the classical Notch target genes Hes1 and Hey1. Tnf-α stimulated canonical NF-κB signaling and, in collaboration with basal Notch signals, induced optimal expression of Notch targets. Mechanistically, Tnf-α stimulation resulted in phosphorylation of histone H3 at the Hes1 promoter, and this signal was lost with Ikk2 deletion. Hes1 suppresses expression of Pparg, which encodes the antiinflammatory nuclear receptor Pparγ. Thus, crosstalk between Tnf-α/Ikk2 and Notch sustains the intrinsic inflammatory profile of transformed cells. These findings reveal what we believe to be a novel interaction between oncogenic inflammation and a major cell fate pathway and show how these pathways can cooperate to promote cancer progression.

Pancreatic ductal adenocarcinoma (PDAC) has a grim prognosis with less than 5% survivors after 5 years. High expression levels of ADAM8, a metalloprotease-disintegrin, are correlated with poor clinical outcome. We show that ADAM8 expression is associated with increased migration and invasiveness of PDAC cells caused by activation of ERK 1/2 and higher MMP activities. For biological function, ADAM8 requires multimerisation and associates with β1-integrin on the cell surface. A peptidomimetic ADAM8 inhibitor, BK-1361, designed by structural modelling of the disintegrin domain, prevents ADAM8 multimerisation. In PDAC cells, BK-1361 affects ADAM8 function leading to reduced invasiveness, and less ERK 1/2 and MMP activation. BK-1361 application in mice decreased tumour burden and metastasis of implanted pancreatic tumour cells and provides improved metrics of clinical symptoms and survival in a KrasG12D-driven mouse model of PDAC. Thus, our data integrate ADAM8 in pancreatic cancer signalling and validate ADAM8 as a target for PDAC therapy.

Alternatively activated macrophages express the pattern recognition receptor scavenger receptor A (SR-A). We demonstrated previously that co-culture of macrophages with tumour cells upregulates macrophage SR-A expression. We show here that macrophage SR-A deficiency inhibits tumour cell migration in a co-culture assay. We further demonstrate that co-culture of tumour-associated macrophages (TAMs) and tumour cells induces secretion of factors which are recognized by SR-A on TAMs. We tentatively identified several potential ligands for the SR-A receptor in tumour cell – macrophage co-cultures by mass spectrometry. Competing with the co-culture induced ligand in our invasion assay recapitulates SR-A deficiency and leads to similar inhibition of tumour cell invasion. In line with our in vitro findings, tumour progression and metastasis is inhibited in SR-A-/- mice in two in vivo models of ovarian and pancreatic cancer. Finally, treatment of tumour-bearing mice with 4F, a small peptide SR-A ligand able to compete with physiological SR-A ligands in vitro, recapitulates the inhibition of tumour progression and metastasis observed in SR-A-/- mice. Our observations suggest that SR-A may be a potential drug target in the prevention of metastatic cancer progression.

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Nuclear factor-βB; (NF-κB) controls a range of genes involved in inflammation, cell survival, growth and apoptosis. The dysregulated NF-κB pathway has been found to be involved in carcinogenesis and cancer progression. An IKKα-deleted mouse pancreatic cancer cell line was generated using a lentiviral construct with an shRNA. We investigated the effects of metformin, an anti-diabetic drug, on the cell proliferation and metabolism of these cells, under normoxic and hypoxic conditions. A high dose (5 mM) of metformin under normoxic conditions suppressed the growth of both wild-type and IKKα knockdown cell types; however, under hypoxic conditions IKKα knockdown cells were more sensitive to treatment than their wild-type counterpart (p < 0.001). Metabolic assays revealed that metformin treatment under normoxic conditions decreased the oxidative phosphorylation (OXPHOS) whilst increasing the lactate production of both cell types to similar levels. Under hypoxia, metformin treatment of both cancer cells resulted in decreased OXPHOS, with a more profound effect on the IKKα knockdown cells, and a significant decrease in lactate production in the IKKα knockdown cells only (p < 0.001). We believe our findings have implications for understanding the molecular mechanisms of metformin as a therapeutic agent in cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3209. doi:1538-7445.AM2012-3209