The role of androgen receptor in breast cancer

The androgen receptor (AR) is a proven clinical target in prostate cancer. Recent research indicates that it is an emerging hormonal target in breast cancer as well, with potential clinical benefit in both estrogen receptor (ER) positive and negative tumors. Compared to the ER, AR contains unique functional domains with relevance to its altered role in human breast cancer. The majority of ER-positive tumors express AR, and a significant percentage of ER-negative tumors might benefit from combined targeting of AR and the ErbB2/HER2 oncogene. Signaling downstream of AR might also affect many clinically important pathways which are also emerging clinical targets in breast cancer. AR expression might also play a role during tumor progression to metastatic disease. The role of AR as a new important biomarker in breast cancer will be reviewed herein.