Synergistic Cytotoxicity between a Protein Kinase C Inhibitor,UCN-01,and Monoclonal Antibody to the Epidermal Growth Factor Receptor on MDA-468 Cells

Abstract

Cytotoxic effect of the monoclonal antibody to the epidermal growth factor receptor (anti-EGFR MAb) given alone or in combination with UCN-01, a selective protein kinase C inhibitor, was investigated in vitro. MDA-468 human breast cancer cells expressing both a large amount of EGF receptors and its ligand, transforming growth factor a, were used. A given number of the cells were plated and treated with the MAb and/or UCN-01 for 48 h. These cells were replated and incubated for colony formation assay. Cytotoxicity of the anti-EGFR MAb alone was hardly detected. However, when cells were treated with both anti-EGFR MAb and UCN-01, the combined cytotoxic effect was synergistic.