13100 Background: The epidermal growth factor receptor (EGFR; ErbB1) and HER-2/neu (ErbB2), members of the ErbB family of receptor tyrosine kinases, are overexpressed in a variety of human tumors and overexpression generally correlates with poor prognosis and decreased survival. Use of inhibitors of these receptors as monotherapies, e.g., trastuzumab, Iressa, and erlotinib, has led to advances in treatment, but many patients do not respond or develop resistance. The anti-apoptotic protein, Bcl-2, is also overexpressed in a number of human tumors. Inhibitors of Bcl-2 induce apoptosis and sensitize cancer cells to other therapies. This study assesses the effects of a combination of a reversible inhibitor of both EGFR and HER-2/neu that is similar to lapatinib (GW2974) and a pan inhibitor of the Bcl-2 family (GX15–070: Gemin X Biotechnologies, Inc.) on the growth of human breast cancer cells. Methods: The MCF-7 human breast cancer cell line transfected with a control vector, MCF/neo, and the HER-2/neu transfected MCF-7 cell line, MCF/18, were treated with various concentrations of GW2974 (0.25–10 μM) and/or the GX15–070 pan Bcl-2 inhibitor (50–500 nM). After a 3 day exposure, cell number was determined using the colorimetric MTT tetrazolium dye assay. Percent of control was normalized to corresponding concentrations of the solvent for both agents (DMSO). Results: Treatment with the GW2974 dual inhibitor or the GX15–070 pan Bcl-2 inhibitor resulted in dose-dependent growth inhibition in both the control and HER-2/neu transfected MCF-7 cell lines. The combination of both agents produced synergistic growth inhibition in both cell lines as confirmed by isobologram analysis. Conclusions: This study has demonstrated synergy with the combination of a dual inhibitor of EGFR and HER-2/neu and an inhibitor of Bcl-2 in control and HER-2/neu overexpressing MCF-7 human breast cancer cells. This finding warrants an evaluation of this combination in clinical trials for the treatment of patients with metastatic breast cancer. [Table: see text]
Identification of differentially expressed genes associated with HER- 2/neu overexpression in human breast cancer cells
