Prediction of synergistic antitumour effect of gefitinib and radiation in vitro.

AIM This study investigated the potential of a series of biomarkers in predicting the interaction of gefitinib and radiation in tumour treatment. MATERIALS AND METHODS In vitro assays were performed on human skin cancer and melanoma cell lines. The antitumour effect was measured by using the MTT assay. Total and phosphorylated epidermal growth factor receptor (EGFR and pEGFR) levels were determined by cell-based ELISA. RESULTS Gefitinib and radiation interacted to inhibit tumour cell proliferation in a cell line-dependent manner. Synergism dominated the interaction (76%), followed by additive effect (20%) and a few instances of antagonism (4%). Correlation analyses revealed a significant correlation between the median combination index (CI) and gefitinib IC₅₀, radiation ID₅₀, gefitinib- or EGF-modulated EGFR and/or pEGFR expression (all p ≤ 0.05). CONCLUSION A potential role of gefitinib efficacy, radiation efficacy and gefitinib- or EGF-modulated EGFR and/or pEGFR expression in the prediction of interaction between gefitinib and radiation is supported.