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HighlightsOxidative stress in the arthritis joint is involved in generating mediators for inflammation.Oxidative stress-induced expression of Cox-2 was mediated by MAPKs and NF-κB.ROS-induced MAPKs and NF-κB were attenuated by inhibition of MAPKKK TAK1.Inhibition of TAK1 activity resulted in reduced expression of Cox-2 and PGE2.ROS-induced TAK1 activation and Cox-2 expression was inhibited by antioxidants N-acetyl cysteamine and hyaluronic acid.

Macrophage stimulating protein (MSP)1 was originally purified from human plasma, based on its activity for murine resident peritoneal macrophages (1). It is a 78-kDa heterodimeric protein composed of a disulfide-linked 53-kDa ␣ chain and a 25-kDa ␤ chain (calculated from amino acid composition). The ␣ chain contains a N-terminal hairpin loop followed by four kringle domains. The ␤ chain has a serine protease-like domain but is devoid of enzymatic activity due to amino acid substitutions in the catalytic triad. MSP belongs to the kringle protein family that includes plasminogen (2) and hepatocyte growth factor/scatter factor (HGF/SF) (3, 4). MSP is synthesized mainly by liver cells (5, 6), circulates in blood as a biologically inactive single chain precursor (7), and is cleaved by members of the kallikrein family (8, 9) or by trypsin-like enzymes located on macrophage surfaces (7). Recent functional studies have revealed that in addition to induction of macrophage shape change, chemotactic migration (10), and phagocytosis of C3bi-coated erythrocytes (1), MSP has other activities. These include inhibition of expression of inducible nitric oxide synthase mRNA in endotoxin or cytokine-stimulated macrophages (11), induction of interleukin-6 production and differentiation of megakaryocytes (12), suppression of colony formation of human bone marrow cells induced by Steel factor plus granulocyte macrophage-stimulating factor (13), increase in beat frequency of nasal epithelium cilia (14), and stimulation in vitro of proliferation of certain epithelial cell lines (15-17).The receptor for MSP was recently identified as the human RON gene product (18), a transmembrane receptor proteintyrosine kinase cloned from a human keratinocyte cDNA library (19). The murine STK gene cloned from hematopoietic stem cells of bone marrow is the homologue of human RON (20,21). The RON gene encodes a 190-kDa heterodimeric protein composed of a 40-kDa extracellular ␣ chain and 150-kDa transmembrane ␤ chain with intrinsic tyrosine kinase activity (21). This property places the product of the RON/STK gene into a subfamily of receptor tyrosine kinases that includes proto-oncogene MET and SEA (22,23). These receptors share many unique structural properties including a putative proteolytic cleavage site, similar location of cysteine residues in their extracellular domain, and two conserved tyrosines in the Cterminal tail (19,20,22,23). Studies of the signaling pathways of RON have shown that tyrosine-phosphorylated RON associates in vivo with intracellular signal transducers, including Grb-2-Sos and phosphatidylinositol 3-kinase (17, 24).In this work, we initiated a structure-activity study of MSP to identify functionally important domains that interact with the RON receptor. Five purified recombinant proteins were used, including pro-MSP, MSP, MSP ␣ and ␤ chains, and the MSP N terminus (including the first two kringles) fused to human IgG Fc. We report the binding capacity of MSP and its subunits to RON receptor in intact cells. We also analyzed ...

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Purpose: Treatment with KRASG12C inhibitors such as sotorasib can produce substantial regression of tumors in some patients with non–small cell lung cancer (NSCLC). These patients require alternative treatment after acquiring resistance to the inhibitor. The mechanisms underlying this acquired resistance are unclear. The purpose of this study was to identify the mechanisms underlying acquired sotorasib resistance, and to explore potential treatments for rescuing patients with sotorasib-resistant KRASG12C NSCLC cells. Experimental Design: Clones of sotorasib-sensitive KRASG12C NSCLC H23 cells exposed to different concentrations of sotorasib were examined using whole-genomic transcriptome analysis, multiple receptor kinase phosphorylation analysis, and gene copy-number evaluation. The underlying mechanisms of resistance were investigated using immunologic examination, and a treatment aimed at overcoming resistance was tested in vitro and in vivo. Results: Unbiased screening detected subclonal evolution of MET amplification in KRASG12C NSCLC cells that had developed resistance to sotorasib in vitro. MET knockdown using small interfering RNA (siRNA) restored susceptibility to sotorasib in these resistant cells. MET activation by its amplification reinforced RAS cycling from its inactive form to its active form. In addition to RAS-mediated MEK–ERK induction, MET induced AKT activation independently of RAS. Crizotinib, a MET inhibitor, restored sensitivity to sotorasib by eliminating RAS–MEK–ERK as well as AKT signaling. MET/KRASG12C dual inhibition led to tumor shrinkage in sotorasib-resistant xenograft mice. Conclusions: MET amplification leads to the development of resistance to KRASG12C inhibitors in NSCLC. Dual blockade of MET and KRASG12C could be a treatment option for MET-amplified, KRASG12C-mutated NSCLC.