Activation of extracellular signal-regulated kinase in lung tissues of mice treated with carcinogen

The activation of extracellular signal-regulated kinase (ERK) in lung tissu es of mice, as determined by the appearance of phosphorylated form, was obs erved on day 30 after urethane injection, and the activation also occurred in urethane-induced lung tumors. Immunohistochemical analysis using anti-ph osphorylated ERK antibody indicated that the active form of ERK localized i n alveolar epithelial cells. Furthermore, we confirmed by immunoprecipitati on and immunoblot analysis that other essential components of the ERK casca de, that is, Ras, Raf and MEK (known as ERK kinase) were activated. These r esults indicate that the activation of the ERK signal in alveolar epithelia l cells at the early stage of urethane-induced lung carcinogenesis Is an im portant factor to develop lung tumors.