To confirm this, various human breast cancer cell lines (SK-BR-3, MCF-7, and MDA-MB-231) and non-cancerous breast epithelial cells (MCF-10A) were treated with FITC-conjugated anti-HER2 monoclonal antibodies, and the fluorescence intensities were compared with those of untreated controls. The gene discussed is ERBB2; the disease is breast cancer.