Genetic mutations that give rise to active mutant forms of Ras are oncogenic and found in several types of tumor. However, such mutations are not clear biomarkers for disease, since they are frequently detected in healthy individuals. Instead, it has become clear that elevated levels of Ras activity are critical for Ras-induced tumorigenesis. However, the mechanisms underlying the production of pathological levels of Ras activity are unclear. Here, we show that in the presence of oncogenic Ras, inflammatory stimuli initiate a positive feedback loop involving NF-κB that further amplifies Ras activity to pathological levels. Stimulation of Ras signaling by typical inflammatory stimuli was transient and had no long-term sequelae in wild-type mice. In contrast, these stimuli generated prolonged Ras signaling and led to chronic inflammation and precancerous pancreatic lesions (PanINs) in mice expressing physiological levels of oncogenic K-Ras. These effects of inflammatory stimuli were disrupted by deletion of inhibitor of NF-κB kinase 2 (IKK2) or inhibition of Cox-2. Likewise, expression of active IKK2 or Cox-2 or treatment with LPS generated chronic inflammation and PanINs only in mice expressing oncogenic K-Ras. The data support the hypothesis that in the presence of oncogenic Ras, inflammatory stimuli trigger an NF-κB-mediated positive feedback mechanism involving Cox-2 that amplifies Ras activity to pathological levels. Because a large proportion of the adult human population possesses Ras mutations in tissues including colon, pancreas, and lung, disruption of this positive feedback loop may be an important strategy for cancer prevention.

The mechanisms which allow cancer cells to adapt to the typical tumor microenvironment of low oxygen and glucose and high lactate are not well understood. GPR81 is a lactate receptor recently identified in adipose and muscle cells that has not been investigated in cancer. In the current study, we examined GPR81 expression and function in cancer cells. We found that GPR81 was present in colon, breast, lung, hepatocellular, salivary gland, cervical and pancreatic carcinoma cell lines. Examination of tumors resected from pancreatic cancer patients indicated that 94% (148/158) expressed high levels of GPR81. Functionally, we observed that the reduction of GPR81 levels using shRNA mediated silencing had little effect on pancreatic cancer cells cultured in high glucose, but led to the rapid death of cancer cells cultured in conditions of low glucose supplemented with lactate. We also observed that lactate addition to culture media induced the expression of genes involved in lactate metabolism including monocarboxylase transporters in control, but not in GPR81 silenced cells. In vivo, GPR81 expression levels correlated with the rate of pancreatic cancer tumor growth and metastasis. Cells in which GPR81 was silenced showed a dramatic decrease in growth and metastasis. Implantation of cancer cells in vivo was also observed to lead to greatly elevate levels of GPR81. These data support that GPR81 is important for cancer cell regulation of lactate transport mechanisms. Furthermore, lactate transport is important for the survival of cancer cells in the tumor microenvironment.

Lipocalin-2 (LCN2) promotes malignant development in many cancer types. LCN2 is upregulated in patients with pancreatic ductal adenocarcinoma (PDAC) and in obese individuals, but whether it contributes to PDAC development is unclear. In this study, we investigated the effects of Lcn2 depletion on diet-induced obesity, inflammation and PDAC development. Mice with acinar cell-specific expression of KrasG12D were crossed with Lcn2-depleted animals and fed isocaloric diets with varying amounts of fat content. Pancreas were collected and analyzed for inflammation, pancreatic intraepithelial neoplasia (PanIN) and PDAC. We also used a syngeneic orthotopic PDAC mouse model to study tumor growth in the presence or absence of Lcn2 expression. In addition, to understand the mechanistic role of how LCN2 could be mediating PDAC, we studied LCN2 and its specific receptor solute carrier family 22 member 17 (SLC22A17) in human pancreatic cancer stellate cells (PSC), key mediators of the PDAC stroma. Depletion of Lcn2 diminished extracellular matrix deposition, immune cell infiltration, PanIN formation and tumor growth. Notably, it also increased survival in both obesity-driven and syngeneic orthotopic PDAC mouse models. LCN2 modulated the secretion of pro-inflammatory cytokines in PSC of the PDAC tumor microenvironment, while downregulation of LCN2-specific receptor SLC22A17 blocked these effects. Our results reveal how LCN2 acts in the tumor microenvironment links obesity, inflammation and PDAC development.

Purpose Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer death. No effective therapy is currently available for PDAC because of the lack of understanding of the mechanisms leading to its growth and development. Inflammatory cells, particularly mast cells have been shown to play key roles in some cancers. We carried out this study to test the hypothesis that mast cells in the tumor microenvironment are essential for PDAC tumorigenesis. Experimental Design The presence of inflammatory cells at various stages of PDAC development was determined in a spontaneous mouse model of PDAC (K-rasG12V). The importance of mast cells was determined using orthotopically implanted PDAC cells in mast cell-deficient Kitw-sh/w-sh mice and further confirmed by reconstitution of wild-type bone marrow-derived mast cells. Clinical relevance was assessed by correlating the presence of mast cells with clinical outcome in patients with PDAC. Results In the spontaneous mouse model of PDAC (K-rasG12V), there was an early influx of mast cells to the tumor microenvironment. PDAC tumor growth was in mast cell-deficient Kitw-sh/w-sh mice, but aggressive PDAC growth was restored when PDAC cells were injected into mast cell-deficient mice reconstituted with wild-type bone marrow-derived mast cells. Mast cell infiltration into the tumor microenvironment was predictive of poor prognosis in patients with PDAC. Conclusions Mast cells play an important role in PDAC growth and development in mouse models and are indicative of poor prognosis in humans, which makes them a potential novel therapeutic target.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the USA, accounting for ,40,000 deaths annually. The dismal prognosis for PDAC is largely due to its late diagnosis. Currently, the most sensitive diagnosis of PDAC requires invasive procedures, such as endoscopic ultrasonography, which has inherent risks and accuracy that is highly operator dependent. Here we took advantage of a general characteristic of solid tumors, the acidic microenvironment that is generated as a by-product of metabolism, to develop a novel approach of using pH (Low) Insertion Peptides (pHLIPs) for imaging of PDAC. We show that fluorescently labeled pHLIPs can localize and specifically detect PDAC in human xenografts as well as PDAC and PanIN lesions in genetically engineered mouse models. This novel approach may improve detection, differential diagnosis and staging of PDAC.A pproximately 45,000 Americans are diagnosed with pancreatic ductal adenocarcinoma (PDAC) each year and the incidences of PDAC are rising 1 . Unfortunately, there has been little progress in the outcomes of patients with PDAC since the 1970s. Surgical resection is the mainstay of therapy; however, only 20% of patients are eligible for resection due to the presence of advanced disease at the time of diagnosis 2 . The lack of specific symptoms (due to the physical position of the organ), and the lack of sensitive and specific biomarkers, make obtaining a diagnosis difficult at an early stage 3 . For these reasons, there is an urgent need for tools to aid in the early and specific detection of PDAC prior to the development of micro-metastatic disease. To date the most commonly used modalities for diagnosing PDAC, including computed tomography (CT), magnetic resonance imaging (MRI) and endoscopic ultrasonography (EUS), are unable to detect early lesions and are mainly used for disease staging 3,4 . In the current study, instead of employing a traditional molecular targeting strategy based on imaging of a single biomarker protein overexpressed in a subset of cancer cells, we evaluated a more general approach for targeting: the acidity of the tumor microenvironment. Acidosis is generated as a by-product of cancer cell metabolism and it is correlated with tumor development and progression [5][6][7] . Imaging the acidic microenvironment avoids the common problem of heterogeneity of protein biomarkers, which limits the usefulness of agents directed to specific cell surface markers 8,9 . We employed recently developed pH-sensitive probes, pH (low) insertion peptides (pHLIPsH) to image PDAC in mice. The pHLIPs are water-soluble membrane peptides, which insert into the lipid bilayer of membranes and form transmembrane helix only within an acidic extracellular microenvironment, such as that found in tumors [10][11][12][13] . We show that the fluorescently-labeled pHLIP probes detected PDAC tumors, metastasis and PanIN lesions in preclinical mouse models of PDAC. The obtained data provide critical proof of principle supporting further development ...

Background and Aims Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death in the USA. Surgical resection is the only effective treatment; however, only 20% of patients are candidates for surgery. The ability to detect early PDAC would increase the availability of surgery and improve patient survival. This study assessed the feasibility of using the enzymatic activity of cathepsin E (Cath E), a protease highly and specifically expressed in PDAC, as a novel biomarker for the detection of pancreas-bearing pancreatic intraepithelial neoplasia (PanIN) lesions and PDAC. Methods Pancreas from normal, chronic pancreatitis and PDAC patients was assessed for Cath E expression by quantitative real-time PCR and immunohistochemistry. Human PDAC xenografts and genetically engineered mouse models (GEMM) of PDAC were injected with a Cath E activity selective fluorescent probe and imaged using an optical imaging system. Results The specificity of Cath E expression in PDAC patients and GEMM of pancreatic cancer was confirmed by quantitative real-time PCR and immunohistochemistry. The novel probe for Cath E activity specifically detected PDAC in both human xenografts and GEMM in vivo. The Cath E sensitive probe was also able to detect pancreas with PanIN lesions in GEMM before tumour formation. Conclusions The elevated Cath E expression in PanIN and pancreatic tumours allowed in-vivo detection of human PDAC xenografts and imaging of pancreas with PanIN and PDAC tumours in GEMM. Our results support the usefulness of Cath E activity as a potential molecular target for PDAC and early detection imaging.

The maxianion channel is widely expressed in many cell types, where it fulfills a general physiological function as an ATP-conductive gate for cell-to-cell purinergic signaling. Establishing the molecular identity of this channel is crucial to understanding the mechanisms of regulated ATP release. A mitochondrial porin (voltage-dependent anion channel (VDAC)) located in the plasma membrane has long been considered as the molecule underlying the maxianion channel activity, based upon similarities in the biophysical properties of these two channels and the purported presence of VDAC protein in the plasma membrane. We have deleted each of the three genes encoding the VDAC isoforms individually and collectively and demonstrate that maxianion channel (ϳ400 picosiemens) activity in VDAC-deficient mouse fibroblasts is unaltered. The channel activity is similar in VDAC1/VDAC3-double-deficient cells and in double-deficient cells with the VDAC2 protein depleted by RNA interference. VDAC deletion slightly down-regulated, but never abolished, the swelling-induced ATP release. The lack of correlation between VDAC protein expression and maxianion channel activity strongly argues against the long held hypothesis of plasmalemmal VDAC being the maxianion channel.Purinergic signaling is a widespread phenomenon of general biological significance, and mechanisms accounting for ATP release from cells remain a contentious issue (1). We have recently identified a maxianion channel as a nanoscopic pore (2) well suited to function as the ATPreleasing pathway (3, 4). This pore accounts for the swelling-induced ATP release from mouse mammary C127 cells (5, 6) and NaCl-dependent ATP-mediated signaling from macula densa to mesangial cells during tubuloglomerular feedback in the kidney (7). In addition, the same pore is operational in swelling-, ischemia-, and hypoxia-induced ATP release from neonatal rat cardiomyocytes (8).The maxianion channel has been observed in a wide variety of cell types and exhibits roughly uniform behavior (9), suggesting that it has a general physiological function. Although the molecular identity of the maxianion channel is not yet firmly established, it is widely held that a voltage-dependent anion channel (VDAC) 2 located in the plasmalemma that normally functions in the mitochondrial outer membrane (10 -12) is the most likely candidate protein. This hypothesis was based on the similarity of shared biophysical properties, such as the large unitary conductance and bell-shaped voltage dependence of the maxianion channel and mitochondrial VDAC (13-18). Corroborating this idea, numerous groups have reported the presence of VDAC protein in the plasma membrane of various cell types (13-26). A possible mechanism for targeting of the same protein to different locations has been suggested by Buettner et al. (14). They reported the existence of an alternative first exon in the murine vdac-1 gene that encodes a different leader peptide at the N terminus, a signal that purportedly targets the protein to the plasma membran...

Anterior gradient 2 (AGR2) promotes cancer growth, metastasis and resistance to therapy via unknown mechanisms. We investigated the effects of extracellular AGR2 signaling through the orphan GPI-linked receptor C4.4A in pancreatic ductal adenocarcinoma (PDAC). Proliferation, migration and invasion and apoptosis were measured using colorimetric, Boyden chamber, and fluorescence-activated cell sorting analyses. We developed blocking monoclonal antibodies against AGR2 and C4.4A and tested their effects, along with siRNAs, on cancer cell functions and on orthotopic tumors in nude mice. Extracellular AGR2 stimulated proliferation, migration, invasion and chemoresistance of PDAC cell lines. AGR2 interacted with C4.4A in cell lysates and mixtures of recombinant proteins. Knockdown of C4.4A reduced migration and resistance to gemcitabine. PDAC tissues, but not adjacent healthy pancreatic tissues, expressed high levels of AGR2 and C4.4A. AGR2 signaling through C4.4A required laminins 1 or 5 and integrin β1. Administration of antibodies against AGR2 and C4.4A reduced growth and metastasis and caused regression of aggressive xenograft tumors leading to increased survival of mice. These data support a model in which AGR2 binds and signals via C4.4A in an autocrine loop and promotes the growth of pancreas tumors in mice. Blocking monoclonal antibodies against AGR2 and C4.4A may have therapeutic potential against PDAC.