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PDF file - 27KB, Sequences of primers used in this study.

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PDF file - 86KB, AREG and TGR5 knockdown in CRC and PDAC cells.

PDF file - 116KB, TGF-alpha is not a critical ligand for DCA-induced EGFR signaling.

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PDF file - 57KB, Schematic model showing the mechanism.

PDF file - 68KB, DCA-mediated Src and EGFR-dependent cell cycle regulation.

PDF file - 104KB, EGFR inhibition in combination with TGR5 silencing decreases STAT3 phosphorylation and cell proliferation.

PDF file - 119KB, AREG inhibition decreases cell proliferation, migration and invasion in CRC and PDAC.

PDF file - 92KB, AREG and TGF-alpha mRNA expression.

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PDF file - 106KB, AREG and TGF-alpha shedding in CRC and PDAC cells.

PDF file - 98KB, Src and EGFR are involved in the AREG and TGF-alpha dependent cell cycle regulation through EGFR signaling.

The nucleotide exchange factor Son of Sevenless (SOS) catalyzes the activation of RAS by converting it from its inactive GDP-bound state to its active GTP-bound state. Recently, we have reported the discovery of small-molecule allosteric activators of SOS1 that can increase the amount of RAS-GTP in cells. The compounds can inhibit ERK phosphorylation at higher concentrations by engaging a feedback mechanism. To further study this process, we sought different chemical matter from an NMR-based fragment screen using selective methyl labeling. To aid this process, several Ile methyl groups located in different binding sites of the protein were assigned and used to categorize the NMR hits into different classes. Hit to lead optimization using an iterative structure-based design paradigm resulted in compounds with improvements in binding affinity. These improved molecules of a different chemical class increase SOS1cat-mediated nucleotide exchange on RAS and display cellular action consistent with our prior results.

Activating mutations in RAS can lead to oncogenesis by enhancing downstream signaling, such as through the MAPK and PI3K pathways. Therefore, therapeutically targeting RAS may perturb multiple signaling pathways simultaneously. One method for modulating RAS signaling is to target the activity of the guanine nucleotide exchange factor SOS1. Our laboratory has discovered compounds that bind to SOS1 and activate RAS. Interestingly, these SOS1 agonist compounds elicit biphasic modulation of ERK phosphorylation and simultaneous inhibition of AKT phosphorylation levels. Here, we utilized multiple chemically distinct compounds to elucidate whether these effects on MAPK and PI3K signaling by SOS1 agonists were mechanistically linked. In addition, we used CRISPR/Cas9 gene-editing to generate clonally derived SOS1 knockout cells and identified a potent SOS1 agonist that rapidly elicited on-target molecular effects at substantially lower concentrations than those causing off-target effects. Our findings will allow us to further define the on-target utility of SOS1 agonists.

Son of sevenless homologue 1 (SOS1) is a guanine nucleotide exchange factor that catalyzes the exchange of GDP for GTP on RAS. In its active form, GTP-bound RAS is responsible for numerous critical cellular processes. Aberrant RAS activity is involved in ~30% of all human cancers; hence, SOS1 is an attractive therapeutic target for its role in modulating RAS activation. Here, we describe a new series of benzimidazole-derived SOS1 agonists. Using structure-guided design, we discovered small molecules that increase nucleotide exchange on RAS in vitro at sub-micromolar concentrations, bind to SOS1 with low double digit nanomolar affinity, rapidly enhance cellular RAS-GTP levels, and invoke biphasic signaling changes in phosphorylation of ERK 1/2. These compounds represent the most potent series of SOS1 agonists reported to date.

Deregulated RAS activity, often the result of mutation, is implicated in approximately 30% of all human cancers. Despite this statistic, no clinically successful treatment for RAS-driven tumors has yet been developed. One approach for modulating RAS activity is to target and affect the activity of proteins that interact with RAS, such as the guanine nucleotide exchange factor (GEF) son of sevenless homologue 1 (SOS1). Here, we report on structure–activity relationships (SAR) in an indole series of compounds. Using structure-based design, we systematically explored substitution patterns on the indole nucleus, the pendant amino acid moiety, and the linker unit that connects these two fragments. Best-in-class compounds activate the nucleotide exchange process at submicromolar concentrations in vitro, increase levels of active RAS–GTP in HeLa cells, and elicit signaling changes in the mitogen-activated protein kinase−extracellular regulated kinase (MAPK–ERK) pathway, resulting in a decrease in pERK1/2T202/Y20...

Secondary bile acids (BA) such as deoxycholic acid (DCA) promote the development of several gastrointestinal malignancies, but how they mediate this effect is unclear. In this study, we offer evidence of a mechanism involving ectodomain shedding of the EGFR ligands amphiregulin (AREG) and TGF-α, which rely upon the cell surface protease TACE/ADAM-17. Specifically, we show that AREG participates in DCA-induced EGFR and STAT3 signaling, cell-cycle progression, and tumorigenicity in human colorectal cancer and pancreatic ductal adenocarcinoma (PDAC). TACE and AREG, but not TGF-α, were overexpressed in both colorectal cancer and PDAC tissues compared with normal tissues. Exposure of colorectal cancer and PDAC cells to DCA resulted in colocalization of Src and TACE to the cell membrane, resulting in AREG-dependent activation of EGFR, mitogen-activated protein kinase (MAPK), and STAT3 signaling. Src or TACE inhibition was sufficient to attenuate DCA-induced AREG, but not TGF-α shedding. We also examined a role for the BA transporter TGR5 in DCA-mediated EGFR and STAT3 signaling. RNA interference-mediated silencing of TGR5 or AREG inhibited DCA-induced EGFR, MAPK, and STAT3 signaling, blunted cyclin D1 expression and cell-cycle progression, and attenuated DCA-induced colorectal cancer or PDAC tumorigenicity. Together, our findings define an AREG-dependent signaling pathway that mediates the oncogenic effects of secondary BAs in gastrointestinal cancers, the targeting of which may enhance therapeutic responses in their treatment. Cancer Res; 74(7); 2062–72. ©2014 AACR.

Introduction: The failure of conventional and molecularly targeted chemotherapeutic regimes to produce meaningful impact on survival in patients with pancreatic cancer (PDAC) highlights a desperate need for novel treatment strategies. A hallmark in PDAC is the presence of a dense desmoplastic reaction (stroma) within the tumor microenvironment (TME) which is characterized by proliferation of fibrotic tissue in which the vasculature functions poorly and impedes the delivery of chemotherapeutic drugs to the tumor cells. STAT3 modulates the transcription of responsive genes involved in the regulation of a variety of critical functions, including cell differentiation, proliferation, apoptosis, angiogenesis, metastasis, and immune responses. We have previously established a mechanistic rationale for activated STAT3 as a biomarker of resistance to cytotoxic and molecularly targeted therapy in PDAC. The purpose of this study was to test whether the delivery and efficacy of gemcitabine could be improved by co-administration of AZD1480, a drug inhibits JAK2/STAT3 signaling. Experimental Procedures: Total and activated STAT3 protein expression was determined in human pancreatic tissues (n=106) and human and genetic mouse pancreatic cell lines generated from PanIn, primary PDAC and liver metastasis. IC50 values for AZD1480, a JAK2/STAT3 inhibitor, was determined against nine human PDAC cell lines and sensitive and resistant cell lines to this agent were identified. Cell lines MiaPACA2, PANC1, CEPAC, Capan1, BxPC3, HPAC and SW1990 were assayed for cell proliferation and apoptosis. The in vitro and in vivo effects of AZD1480 on multiple signaling pathways, downstream effectors and tumorigenicity in PDAC were investigated. Knockdown and over expressed STAT3 cells were developed and assayed for tumorigenicity and multiple downstream effectors with or without gemcitabine. In vivo effects of AZD1480, gemcitabine or the combination was determined on xenografts of BxPC3 and PANC1 cells. In vivo expression of pSTAT3, cleaved caspase3 and Ki67 were studied by immunohistochemistry and drug delivery was analyzed by imaging MALDI-mass-spectometry. Results: STAT3 activation is necessary for the malignant phenotype and affects survival in PDAC. The combination of AZD1480 and gemcitabine resulted in cooperative inhibition of cell migration and invasion of both sensitive and resistant PDAC cells at concentrations that were ineffective as individual agents. Treatment with AZD1480 resulted in inhibition of VEGF and stromal markers SPARC and fibronectin. The combined treatment of AZD1480 and gemcitabine enhanced inhibition of growth of resistant tumor xenografts in vivo. Furthermore, combined treatment of AZD1480 and gemcitabine increased drug delivery to the resistant pancreas tumor tissues in vivo. Conclusions: These results provide evidence that targeted JAK2/STAT3 inhibition with AZD1480, in addition to cytotoxic gemcitabine chemotherapy, inhibits the tumor stroma and enhances in vivo drug delivery to the tumor resulting in improved therapeutic response of PDAC. Citation Format: Nagaraj Nagathihalli, Yugandhar Beesetty, Michelle Reyzer, Chanjuan Shi, Richard Caprioli, Nipun Merchant. JAK2 inhibition blocks STAT3 signaling and enhances drug delivery and therapeutic response in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Progress and Challenges; Jun 18-21, 2012; Lake Tahoe, NV. Philadelphia (PA): AACR; Cancer Res 2012;72(12 Suppl):Abstract nr B32.

The arbuscular mycorrhizal (AM) symbiosis, formed between the majority of land plants and ubiquitous soil fungi of the phylum Glomeromycota, is responsible for massive nutrient transfer and global carbon sequestration. AM fungi take up nutrients from the soil and exchange them against photosynthetically fixed carbon (C) from the host. Recent studies have demonstrated that reciprocal reward strategies by plant and fungal partners guarantee a “fair trade” of phosphorus against C between partners [Kiers ET, et al. (2011) Science 333:880–882], but whether a similar reward mechanism also controls nitrogen (N) flux in the AM symbiosis is not known. Using mycorrhizal root organ cultures, we manipulated the C supply to the host and fungus and followed the uptake and transport of N sources in the AM symbiosis, the enzymatic activities of arginase and urease, and fungal gene expression in the extraradical and intraradical mycelium. We found that the C supply of the host plant triggers the uptake and transport of N in the symbiosis, and that the increase in N transport is orchestrated by changes in fungal gene expression. N transport in the symbiosis is stimulated only when the C is delivered by the host across the mycorrhizal interface, not when C is supplied directly to the fungal extraradical mycelium in the form of acetate. These findings support the importance of C flux from the root to the fungus as a key trigger for N uptake and transport and provide insight into the N transport regulation in the AM symbiosis.

Background & Aims A hallmark of pancreatic ductal adenocarcinoma (PDAC) is the presence of a dense desmoplastic reaction (stroma) that impedes drug delivery to the tumor. Attempts to deplete the tumor stroma have resulted in formation of more aggressive tumors. We have identified signal transducer and activator of transcription (STAT) 3 as a biomarker of resistance to cytotoxic and molecularly targeted therapy in PDAC. The purpose of this study is to investigate the effects of targeting STAT3 on the PDAC stroma and on therapeutic resistance. Methods Activated STAT3 protein expression was determined in human pancreatic tissues and tumor cell lines. In vivo effects of AZD1480, a JAK/STAT3 inhibitor, gemcitabine or the combination were determined in Ptf1a cre/+ ;LSL-Kras G12D/+ ;Tgfbr2 flox/flox (PKT) mice and in orthotopic tumor xenografts. Drug delivery was analyzed by matrix-assisted laser desorption/ionization imaging mass spectrometry. Collagen second harmonic generation imaging quantified tumor collagen alignment and density. Results STAT3 activation correlates with decreased survival and advanced tumor stage in patients with PDAC. STAT3 inhibition combined with gemcitabine significantly inhibits tumor growth in both an orthotopic and the PKT mouse model of PDAC. This combined therapy attenuates in vivo expression of SPARC, increases microvessel density, and enhances drug delivery to the tumor without depletion of stromal collagen or hyaluronan. Instead, the PDAC tumors demonstrate vascular normalization, remodeling of the tumor stroma, and down-regulation of cytidine deaminase. Conclusions Targeted inhibition of STAT3 combined with gemcitabine enhances in vivo drug delivery and therapeutic response in PDAC. These effects occur through tumor stromal remodeling and down-regulation of cytidine deaminase without depletion of tumor stromal content.

International audience; Plants and their arbuscular mycorrhizal fungal symbionts interact in complex underground networks involving multiple partners. This increases the potential for exploitation and defection by individuals, raising the question of how partners maintain a fair, two-way transfer of resources. We manipulated cooperation in plants and fungal partners to show that plants can detect, discriminate, and reward the best fungal partners with more carbohydrates. In turn, their fungal partners enforce cooperation by increasing nutrient transfer only to those roots providing more carbohydrates. On the basis of these observations we conclude that, unlike many other mutualisms, the symbiont cannot be "enslaved." Rather, the mutualism is evolutionarily stable because control is bidirectional, and partners offering the best rate of exchange are rewarded.

181 Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most difficult human malignancies to treat due to its intrinsic (de novo) and extrinsic (acquired) chemoresistance. We have previously identified constitutively activated STAT3 as a mediator of treatment resistance. Src or EGFR activate STAT3 and promote STAT3 mediated tumor progression and mediate communication within the tumor microenvironment (TME). The purpose of this study was to further understand the molecular mechanisms of stromal-mediated chemoresistance in PDAC to generate new and promising targeted therapies. Methods: We characterized the expression of total and activated STAT3 and MAPK proteins in human pancreatic tissues (n=106), PDAC cell lines (n=9) and in PanIn lesions, primary PDAC and liver metastasis cell lines generated from tumors established in genetically engineered mice. Effects of STAT3 and MAPK inhibition (drug or siRNA) were assessed for phosphorylation of STAT3, Src, MAPK, EGFR and GSK3β and expression of cyclin-D1, SPARC, VEGF, fibronectin, CD31 and tumorigenicity in vitro and in vivo. Results: STAT3 activation is necessary for the malignant phenotype and affects survival in PDAC. In both human and mouse PDAC cell lines and tissues, there is an inverse correlation between activation of STAT3 on MAPK and GSK3β signaling. Inhibition of STAT3 reciprocally activated MAPK, GSK3β, Src and EGFR which led to subsequent reactivation of STAT3. Targeting both STAT3 and MAPK inhibited activation of STAT3, MAPK, GSK3β, Src, EGFR and cyclin-D1. Combined inhibition of STAT3 and MAPK overcame STAT3 mediated resistance and resulted in synergistic inhibition of tumorigenicity as well as inhibition of the tumor stroma, angiogenesis and hypoxia within the TME. Conclusions: The mechanism of STAT3-mediated treatment resistance is dependent on activation of MAPK signaling which in turn leads to reactivation of multiple oncogenic signaling pathways. Combined inhibition of STAT3 and MAPK overcomes therapeutic resistance, targets the TME and reduces tumorigenicity in PDAC. Targeting STAT3 and MAPK is a potent treatment regimen and may be a novel approach to enhance drug delivery and improve therapeutic response in PDAC.