In vitro antiproliferative effect of trastuzumab (Herceptin®) combined with cetuximab (Erbitux®) in a model of human non-small cell lung cancer expressing EGFR and HER2

Lung cancer is the leading cause of cancer death. For this reason, new therapies are needed for the treatment of this devastating disease. In this study, we investigated the effects of combining cetuximab and the trastuzumab on the growth of a model of human non-small cell lung carcinoma cell line (A549). The results were compared with those obtained from a human lung squamous carcinoma cell line (NCI-H226). Both cell lines were treated with cetuximab and trastuzumab, alone or in combination, at various concentrations, for 24, 48 and 72 h. Cell proliferation was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. EGFR and HER-2 mRNA expression was detected by reverse transcription polymerase chain reaction, and the gene amplification status of receptors was evaluated by fluorescence in situ hybridisation. The colorimetric proliferation assay showed that trastuzumab combined with cetuximab significantly inhibited A549 cells at a dose of 40 μg/ml after 72 h of treatment (p < 0.05), while no time-dose dependent inhibition was observed in NCI-H226 cells. The combined treatment influenced both levels of EGFR and HER-2 mRNA in A549 cells and only EGFR mRNA levels in NCI-H226 cells. Fluorescence in situ hybridisation showed that both cell lines were aneuploid for the two genes with equally increased EGFR and CEN7 signals, as well as HER-2 and CEN17 signals, indicating a condition of polysomy without amplification. The preliminary results of this study encourage further investigations to elucidate the downstream events involved and to understand how these mechanisms influence non-small cell lung cancers growth.