Inhibition of Integrin αvβ6, an Activator of Latent Transforming Growth Factor-β, Prevents Radiation-induced Lung Fibrosis

Rationale: In experimental models, lung fibrosis is dependent on transforming growth factor (TGF)-β signaling. TGF-β is secreted in a latent complex with its propeptide, and TGF-β activators release TGF-β from this complex. Because the integrin αvβ6 is a major TGF-β activator in the lung, inhibition of αvβ6-mediated TGF-β activation is a logical strategy to treat lung fibrosis.Objectives: To determine, by genetic and pharmacologic approaches, whether murine radiation-induced lung fibrosis is dependent on αvβ6.Methods: Wild-type mice, αvβ6-deficient (Itgb6−/−) mice, and mice heterozygous for a Tgfb1 mutation that eliminates integrin-mediated activation (Tgfb1+/RGE) were exposed to 14 Gy thoracic radiation. Some mice were treated with an anti-αvβ6 monoclonal antibody or a soluble TGF-β receptor fusion protein. αvβ6 expression was determined by immunohistochemistry. Fibrosis, inflammation, and gene expression patterns were assessed 20–32 weeks postirradiation.Measurements and Main Results: β6 Integrin expres...