Abstract
TGF-β1 signaling is a critical driver of collagen accumulation and fibrotic disease but also a vital suppressor of inflammation and epithelial cell proliferation. The nature of this multifunctional cytokine has limited the development of global TGF-β1 signaling inhibitors as therapeutic agents. We conducted phenotypic screens for small molecules that inhibit TGF-β1-induced epithelial-mesenchymal transition without immediate TGF-β1 receptor (TβR) kinase inhibition. We identified trihydroxyphenolic compounds as potent blockers of TGF-β1 responses (IC50 ~50 nM), Snail1 expression, and collagen deposition in vivo in models of pulmonary fibrosis and collagen-dependent lung cancer metastasis. Remarkably, the functional effects of trihydroxyphenolics required the presence of active lysyl oxidase-like 2 (LOXL2), thereby limiting effects to fibroblasts or cancer cells, the major LOXL2 producers. Mechanistic studies revealed that trihydroxyphenolics induce auto-oxidation of a LOXL2/3-specific lysine (K731) in a time-dependent reaction that irreversibly inhibits LOXL2 and converts the trihydrophenolic to a previously undescribed metabolite that directly inhibits TβRI kinase. Combined inhibition of LOXL2 and TβRI activities by trihydrophenolics resulted in potent blockade of pathological collagen accumulation in vivo without the toxicities associated with global inhibitors. These findings elucidate a therapeutic approach to attenuate fibrosis and the disease-promoting effects of tissue stiffness by specifically targeting TβRI kinase in LOXL2-expressing cells.
MeSH terms
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A549 Cells
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Amino Acid Oxidoreductases / genetics
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Amino Acid Oxidoreductases / metabolism
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Animals
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Drug Screening Assays, Antitumor
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Enzyme Inhibitors* / chemistry
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Enzyme Inhibitors* / pharmacology
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Epithelial-Mesenchymal Transition*
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Fibroblasts / metabolism*
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Fibroblasts / pathology
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Humans
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Lung Neoplasms* / drug therapy
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Lung Neoplasms* / genetics
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Lung Neoplasms* / metabolism
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Mice
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Neoplasm Metastasis
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Neoplasm Proteins / antagonists & inhibitors*
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Neoplasm Proteins / genetics
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Neoplasm Proteins / metabolism*
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Phenols / chemistry
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Phenols / pharmacology
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Protein Kinase Inhibitors / pharmacology
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Protein Serine-Threonine Kinases / antagonists & inhibitors*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Pulmonary Fibrosis* / drug therapy
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Pulmonary Fibrosis* / genetics
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Pulmonary Fibrosis* / metabolism
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Pulmonary Fibrosis* / pathology
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Receptor, Transforming Growth Factor-beta Type I
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Receptors, Transforming Growth Factor beta / antagonists & inhibitors*
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Receptors, Transforming Growth Factor beta / genetics
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Receptors, Transforming Growth Factor beta / metabolism
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Signal Transduction / drug effects*
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Transforming Growth Factor beta1 / antagonists & inhibitors
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Transforming Growth Factor beta1 / genetics
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Transforming Growth Factor beta1 / metabolism*
Substances
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Enzyme Inhibitors
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Neoplasm Proteins
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Phenols
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Protein Kinase Inhibitors
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Receptors, Transforming Growth Factor beta
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TGFB1 protein, human
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Tgfb1 protein, mouse
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Transforming Growth Factor beta1
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Amino Acid Oxidoreductases
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LOXL2 protein, human
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Loxl2 protein, mouse
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Protein Serine-Threonine Kinases
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Receptor, Transforming Growth Factor-beta Type I