Abstract
Asbestos fibers are human carcinogens with undefined mechanisms of action. In studies here, we examined signal transduction events induced by asbestos in target cells of mesothelioma and potential cell surface origins for these cascades. Asbestos fibers, but not their nonfibrous analogues, induced protracted phosphorylation of the mitogen-activated protein (MAP) kinases and extracellular signal-regulated kinases (ERK) 1 and 2, and increased kinase activity of ERK2. ERK1 and ERK2 phosphorylation and activity were initiated by addition of exogenous epidermal growth factor (EGF) and transforming growth factor-α, but not by isoforms of platelet-derived growth factor or insulin-like growth factor-1 in mesothelial cells. MAP kinase activation by asbestos was attenuated by suramin, which inhibits growth factor receptor interactions, or tyrphostin AG 1478, a specific inhibitor of EGF receptor tyrosine kinase activity (IC50 = 3 nm). Moreover, asbestos caused autophosphorylation of the EGF receptor, an event triggering the ERK cascade. These studies are the first to establish that a MAP kinase signal transduction pathway is initiated after phosphorylation of a peptide growth factor receptor following exposure to asbestos fibers.
Footnotes
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↵1 This research was supported in part by Grant RO1 ES0006499 from the National Institute of Environmental Health Sciences, Environmental Pathology Training Grant T3207122 from the National Institute of Environmental Health Sciences, and Grant R01 HL39 469 from the National Heart, Lung, and Blood Institute.
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↵2 To whom requests for reprints should be addressed, at Department of Pathology, Medical Alumni Building, University of Vermont College of Medicine, Burlington, Vermont 05405. Phone: (802) 656-0535; Fax: (802) 656-8892.
- Received July 22, 1996.
- Accepted October 17, 1996.
- ©1996 American Association for Cancer Research.
Volume 56, Issue 23
