Gamma-irradiation induces HER-2/neu overexpression in breast cancer cell lines and sensitivity to treatment with trastuzumab.

Purpose: Overexpression of human epidermal growth factor receptor-2 (HER-2/neu) in breast cancer patients is a prerequisite for treatment with trastuzumab. In the present study, we demonstrate by fluorescence in situ hybridization (FISH) analysis that HER-2/neu gene amplification and chromosome 17 (CEP17) polysomy can be induced by irradiation in human breast cancer cell lines with low basal level of HER-2/neu.

Materials And Methods: The irradiation-induced HER-2/neu gene amplification and CEP17 polysomy enhanced HER-2/neu at the protein level in both human MDA-MB-231 and MDA-MB-435 breast cancer cell lines which was determined by immunohistochemistry and fluorescence analysis and was correlated with mRNA levels.