Recent studies clearly described that the interactions between HER-2/neu and cyclin D1 appear to have therapeutic relevance because several phytochemical or synthetic drugs reduced cyclin D expression through the inhibition of HER-2/neu, and the anti-HER-2/neu monoclonal antibody trastuzumab (Herceptin) reduces cyclin D1 protein levels in human breast cancer cells [36, 37]. The gene discussed is ERBB2; the disease is breast cancer.