A Study of the cytotoxic effects of cetuximab and the interaction with a selective Cox-2 inhibitor (Celecoxib) in breast cancer cell lines.

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OBJECTIVES: Direct modulation of signal transduction pathways by Epidermal Growth Factor (EGF) and its family members, as well as their indirect regulation by other unrelated mediators are critical during cancer cells development. In addition, there has been a growing body of data indicating a role of Cyclooxygenase (COX) -2 in carcinogenesis. The purpose of this study was to assess the antiproliferative effect of Cetuximab, a monoclonal antibody that binds the extracellular domain of the EGF receptor (EGFR), and to evaluate the interaction between Cetuximab and Celecoxib. METHODS: Increasing doses of Cetuximab (0.5 100 mg/ml) and Celecoxib (5 40 mM) were tested alone and in combination against human breast cancer cell lines, including BT20 which has an amplification of the EGFR, and MCF-7 which expresses low levels of the receptor. Inhibition of cell growth after 7 days of treatment was assessed by the MTT colorimetric assay, while apoptosis was detected using an in situ DNA Fragmentation Detection kit. RESULTS: Cetuximab inhibited the growth of BT20 by as much as 35% compared to only 15% in the MCF-7 cell line (p < 0.001). In addition, BT20 cell lines showed a dose-dependent response to Cetuximab. Additive cell growth inhibition was noticed with the combination of Cetuximab and Celecoxib. For example, a 48.2% growth inhibition was seen with the combination as compared to only 29.8% and 27.8% for Cetuximab (0.5 mg/ml) and Celecoxib (20 mM) respectively (p < 0.001, oneway ANOVA). The apoptosis assay showed 6.0 fold increase in apoptosis with the combination compared with control. CONCLUSION: Cetuximab has activity in a human breast cancer cell line, which has an amplification of the EGFR. Addition of the selective COX-2 inhibitor, Celecoxib to Cetuximab potentiates its antiproliferative effect in vitro. The cytotoxicity was paralleled by an increase in apoptosis, suggesting that this process is one of the underlying mechanisms. This additive effect may have clinical relevance in certain EGFR- overexpressing breast cancers, and should be further investigated.