The urokinase plasminogen activator binds to its cellular receptor with high affinity and initiates signaling cascades that are implicated in pathological processes including tumor growth, metastasis, and inflammation. We report the crystal structure at 1.9 angstroms of the urokinase receptor complexed with the urokinase amino-terminal fragment and an antibody against the receptor. The three domains of urokinase receptor form a concave shape with a central cone-shaped cavity where the urokinase fragment inserts. The structure provides insight into the flexibility of the urokinase receptor that enables its interaction with a wide variety of ligands and a basis for the design of urokinase-urokinase receptor antagonists.

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Summary Oncogenic mutations in two isocitrate dehydrogenase (IDH)-encoding genes (IDH1 and IDH2) have been identified in acute myelogenous leukemia, low-grade glioma, and secondary glioblastoma (GBM). Our in silico and wet-bench analyses indicate that non-mutated IDH1 mRNA and protein are commonly overexpressed in primary GBM. We show that genetic and pharmacologic inactivation of IDH1 decreases GBM cell growth, promotes a more differentiated tumor cell state, increases apoptosis in response to targeted therapies, and prolongs survival of animal subjects bearing patient-derived xenografts (PDXs). On a molecular level, diminished IDH1 activity results in reduced α-ketoglutarate (αKG) and NADPH production, paralleled by deficient carbon flux from glucose or acetate into lipids, exhaustion of reduced glutathione, increased levels of reactive oxygen species (ROS), and enhanced histone methylation and differentiation marker expression. These findings suggest that IDH1 upregulation represents a common metabolic adaptation by GBM to support macromolecular synthesis, aggressive growth, and therapy resistance.

Superoxide dismutase 1 (SOD1) is an abundant copper/zinc enzyme found in the cytoplasm that converts superoxide into hydrogen peroxide and molecular oxygen. Tetrathiomolybdate (ATN-224) has been recently identified as an inhibitor of SOD1 that attenuates FGF-2-and VEGF-mediated phosphorylation of ERK1/2 in endothelial cells. However, the mechanism for this inhibition was not elucidated. Growth factor (GF) signaling elicits an increase in reactive oxygen species (ROS), which inactivates protein tyrosine phosphatases ( angiogenesis ͉ cancer ͉ redox ͉ tetrathiomolybdate ͉ ATN-224

Approximately 85% of lung cancers are non-small-cell lung cancers (NSCLCs), which are often diagnosed at an advanced stage and associated with poor prognosis. Currently, there are very few therapies available for NSCLCs due to the recalcitrant nature of this cancer. Mutations that activate the small GTPase KRAS are found in 20% to 30% of NSCLCs. Here, we report that inhibition of superoxide dismutase 1 (SOD1) by the small molecule ATN-224 induced cell death in various NSCLC cells, including those harboring KRAS mutations. ATN-224-dependent SOD1 inhibition increased superoxide, which diminished enzyme activity of the antioxidant glutathione peroxidase, leading to an increase in intracellular hydrogen peroxide (H 2 O 2 ) levels. We found that ATN-224-induced cell death was mediated through H 2 O 2 -dependent activation of P38 MAPK and that P38 activation led to a decrease in the antiapoptotic factor MCL1, which is often upregulated in NSCLC. Treatment with both ATN-224 and ABT-263, an inhibitor of the apoptosis regulators BCL2/BCLXL, augmented cell death. Furthermore, we demonstrate that ATN-224 reduced tumor burden in a mouse model of NSCLC. Our results indicate that antioxidant inhibition by ATN-224 has potential clinical applications as a single agent, or in combination with other drugs, for the treatment of patients with various forms of NSCLC, including KRAS-driven cancers. IntroductionLung cancer is the leading cause of cancer deaths in the United States and worldwide. Non-small-cell lung cancers (NSCLCs) represent 80% of all lung cancers and are often diagnosed at an advanced stage with poor prognosis. Adenocarcinoma, a subtype of NSCLC, is the most common form of lung cancer and is characterized by activating mutations in the KRAS proto-oncogene in 20% to 30% of cases and by inactivating mutations in the tumor suppressor TP53 in 50% of cases (1).With the goal of identifying new therapies for NSCLCs, a largescale chemical screen recently identified a small molecule that selectively induced cell death in oncogenic KRAS-driven (KRAS onc -driven) cancer cells compared with normal cells. The small molecule induced cell death by increasing intracellular ROS (2). However, the mechanism by which ROS was induced and caused cell death has not yet been established. Also, it is known that oncogenic-driven cancer cells generate increased ROS as byproducts of their augmented metabolism to promote and maintain tumorigenicity (3-5). Since high levels of ROS can induce cell death (2, 6), cancer cells adapt to ROS stress by upregulating intracellular antioxidant proteins (7-10) in order to maintain ROS levels that allow protumorigenic signaling without inducing cell death. This reliance on antioxidants potentially makes cancer cells selectively vulnerable to antioxidant inhibition, as nontransformed cells generate lower basal levels of ROS and are therefore less dependent on their detoxification. In fact, studies have shown that disabling antioxidant mechanisms triggers ROS-mediated cell death in a variety of cancer cell ty...

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the intestinal tract with unknown multifactorial etiology that, among other things, result in alteration and dysfunction of the intestinal microvasculature. Clinical observations of increased colon microvascular density during IBD have been made. However, there have been no reports investigating the physiological or pathological importance of angiogenic stimulation during the development of intestinal inflammation. Here we report that the dextran sodium sulfate and CD4+CD45RBhigh T-cell transfer models of colitis stimulate angiogenesis that results in increased blood vessel density concomitant with increased histopathology, suggesting that the neovasculature contributes to tissue damage during colitis. We also show that leukocyte infiltration is an obligatory requirement for the stimulation of angiogenesis. The angiogenic response during experimental colitis was differentially regulated in that the production of various angiogenic mediators was diverse between the two models with only a small group of molecules being similarly controlled. Importantly, treatment with the anti-angiogenic agent thalidomide or ATN-161 significantly reduced angiogenic activity and associated tissue histopathology during experimental colitis. Our findings identify a direct pathological link between angiogenesis and the development of experimental colitis, representing a novel therapeutic target for IBD.

The urokinase receptor (uPAR) can recognize several ligands. The structural basis for this multiple ligand recognition by uPAR is unknown. This study reports the crystal structures of uPAR in complex with both urokinase (uPA) and vitronectin and reveal that uPA occupies the central cavity of the receptor, whereas vitronectin binds at the outer side of the receptor. These results provide a structural understanding of one receptor binding to two ligands.

The urokinase receptor (uPAR) binds urokinase-type plasminogen activator (u-PA) through specific interactions with uPAR domain 1, and vitronectin through interactions with a site within uPAR domains 2 and 3. These interactions promote the expression of cell surface plasminogen activator activity and cellular adhesion to vitronectin, respectively. High molecular weight kininogen (HK) also stimulates the expression of cell surface plasminogen activator activity through its ability to serve as an acquired receptor for prekallikrein, which, after its activation, may directly activate prourokinase. Here, we report that binding of the cleaved form of HK (HKa) to human umbilical vein endothelial cells (HUVEC) is mediated through zinc-dependent interactions with uPAR. These occur through a site within uPAR domains 2 and 3, since the binding of 125 I-HKa to HUVEC is inhibited by vitronectin, anti-uPAR domain 2 and 3 antibodies and soluble, recombinant uPAR (suPAR), but not by antibody 7E3, which recognizes the ␤ chain of the endothelial cell vitronectin receptor (integrin ␣ v ␤ 3 ), or fibrinogen, another ␣ v ␤ 3 ligand. We also demonstrate the formation of a zinc-dependent complex between suPAR and HKa. Interactions of HKa with endothelial cell uPAR may underlie its ability to promote kallikrein-dependent cell surface plasmin generation, and also explain, in part, its antiadhesive properties. (