Because AR ablation in myofibers using a promoter region derived from the human α-skeletal actin (HSA) gene (HSA-Cre;ARL2/Y mice) also leads to reduced LA/BC mass (27), we generated HSA-Cre;PDGFRα-CreER;ARL2/Y mice to examine whether the weight reduction depended on AR in myofibers. The gene discussed is AR; the disease is breast cancer.