A study using Cre/LoxP-mediated conditional deletion of the Ar allele in mammary epithelium demonstrated that reduced epithelial AR expression also promoted the early onset of Neu (ERBB2) proto-oncogene tumors [32], suggesting that the AR in mammary epithelial cells may have a significant role in AR-dependent protection against experimental breast cancer. The gene discussed is ERBB2; the disease is breast cancer.