Molecular Mechanisms of Action of Imatinib Mesylate in Human Ovarian Cancer: A Proteomic Analysis

Background: Imatinib mesylate (Gleevec®, Novartis, Basel, Switzerland) is a small-molecule tyrosine kinase inhibitor with activity against ABL, BCR-ABL, c-KIT, and PDGFRα. Several clinical trials have evaluated the efficacy and safety of imatinib in patients with ovarian carcinoma who have persistent or recurrent disease following front-line platinum/taxane based chemotherapy. However, there is limited pre-clinical and clinical data on the molecular targets and action of imatinib in ovarian cancer. Materials and Methods: Human ovarian cancer cells (A2780) were treated with imatinib mesylate for either 6 or 24 h. We employed a 2D (two-dimensional) gel electrophoresis and mass spectrometry-based proteomics approach to identify protein expression patterns and signaling pathways that were altered in response to imatinib. Cells were analyzed for PDGFRα and AKT expression, which were then correlated with imatinib sensitivity. Results: Using 2D gel electrophoresis of overlapping pH ranges from pH 4 to 11, about 4,000 protein spots could be analyzed reproducibly. Proteins whose levels changed between two fold to 30 fold were grouped according to whether changes were in the same direction at both time points of treatment with respect to the control, or changed their levels only at one of the time points. Conclusion: Differentially regulated proteins following imatinib treatment of A2780 cells involved the regulation of actin cytoskeleton, metabolic pathways, cell cycle, cell proliferation, apoptosis, cell junctions, and signal transduction. Thus, exposure of cells to imatinib produces complex changes in the cell that require further investigation.