title: Activation of the PI3K-AKT pathway in human malignant mesothelioma cells.
abstract: Malignant mesothelioma (MM) is a highly aggressive neoplasm, which is associated with asbestos exposure. The dysregulated phosphatidylinositol 3-kinase (PI3K)-AKT pathway plays an important role in cell proliferation, survival and motility in various cancers. In this study, we analyzed the activation status and underlying mechanisms of this pathway in MM cells using 21 cell lines. AKT activation was observed in 13 (62%) of the 21 MM cell lines under serum-starved conditions. Two cell lines, ACC-MESO-1 and Y-MESO-25, showed no expression of PTEN protein, while 7 other cell lines showed low expression of PTEN mRNA and protein compared to expression levels in an immortalized normal mesothelial cell line, MeT-5A. We found that PTEN inactivation in the ACC-MESO-1 and Y-MESO-25 lines was due to a 39.4-kb deletion including PTEN exon 2, and to a 7.7-kb deletion including exon 1, respectively. Re-expression of PTEN in these cells reduced the activity of colony formation in vitro. In contrast, no mutation of PIK3CA or LKB1 was found in any of the MM cell lines. These findings suggest that AKT is frequently activated in MM cells, in part due to the downregulation of PTEN. Thus, the PI3K-AKT signaling pathway is a potential therapeutic target for MM.
authors.affiliation: Division of Molecular Oncology, Aichi Cancer Center Research Institute, Nagoya 464-8681, Japan.
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Hideki
authors.initials: H
authors.lastname: Murakami
authors.forename: Koji
authors.initials: K
authors.lastname: Kawaguchi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Tanigushi
authors.forename: Makiko
authors.initials: M
authors.lastname: Fujii
authors.forename: Keiko
authors.initials: K
authors.lastname: Shinjo
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kondo
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Osada
authors.forename: Kaoru
authors.initials: K
authors.lastname: Shimokata
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Horio
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Hida
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Sekido