Asbestos-induced mesothelial injury and carcinogenesis: Involvement of iron and reactive oxygen species.

Asbestos fibers have been used as an industrial and construction material worldwide due to their high durability and low production cost. Commercial usage of asbestos is currently prohibited in Japan; however, the risk of asbestos-induced malignant mesothelioma (MM) remains. According to epidemiological data, the onset of MM is estimated to occur after a latent period of 30-40 years from initial exposure to asbestos fibers; thus, the continuous increase in MM is a concern. To explore the molecular mechanisms of MM using animal models, iron saccharate with iron chelator-induced sarcomatoid mesothelioma (SM) revealed hallmarks of homozygous deletion of Cdkn2a/2b by aCGH and microRNA-199/214 by expression microarray. Oral treatment of iron chelation by deferasirox decreased the rate of high-grade SM. Moreover, phlebotomy delayed MM development in crocidolite-induced MM in rats. In Divalent metal transporter 1 (Dmt1) transgenic mice, MM development was delayed because of low reactive oxygen species (ROS) production. These results indicate the importance of iron and ROS in mesothelial carcinogenesis. The aims of this review focus on the pathogenesis of elongated mineral particles (EMPs), including asbestos fibers and multiwalled carbon nanotubes (MWCNTs) that share similar rod-like shapes in addition to the molecular mechanisms of MM development.