Abl kinase but not PI3-kinase links to the cytoskeletal defects in Bcr-Abltransformed cells

Objective. The purpose of this study was to investigate the contribution of Abl kinase and phosphatidylinositol 3-kinase (PI3-kinase) to the altered a dhesive properties and cytoskeletal defects in a Bcr-Abl transformed fibrob last cell model. Materials and Methods. Two fibroblast cell lines stably transfected with Bc r-Abl were compared to their parental counterparts for alterations in their adhesive properties in an attachment assay and for abnormalities in their cytoskeletal architecture by immunofluorescence microscopy. Cells then were treated with specific inhibitors of either the Abl kinase CGP57148 or the PI3-kinase LY294002 to determine whether these treatments would restore nor mal cytoarchitecture and adhesion, Significant defects in cytoskeletal arch itecture were observed using this fibroblast model of Bcr-Abl expression. S pecific changes include loss of stress fibers and focal adhesions, which co rrelated with an adhesive defect. Results, Treatment of Bcr-Abt expressing cells with CGP57148, but not LY294 002, resulted in reversion of cells to a near-normal phenotype, as assessed by immunofluorescence and attachment of Bcr-Abl transformed fibroblasts, Conlclusions. Our studies demonstrate that Bcr-Abl tyrosine kinase but not PI3- kinase activity is required for maintenance of cytoskeletal rearrangem ents resulting from Bcr-Abl expression, Further, inhibition of Abl kinase r estored normal adhesive properties to the Bcr-Abl-expressing cells, demonst rating the contribution of Bcr-Abl kinase activity to abnormal cytoskeletal function. (C) 2000 International Society for Experimental Hematology. Publ ished by Elsevier Science Inc.