Sex
steroids play important roles in the development of human
breast carcinoma.
Androgen receptor (AR) is expressed in a majority of
breast carcinoma tissues. However, the significance of
androgen actions remains largely unclear in
breast carcinoma, differing from
estrogen actions. Therefore, in this review, we summarized recent studies on
androgens in
breast carcinoma. Concentration of a potent
androgen, 5alpha-dihydrotestosterone (DHT), was significantly higher in
breast carcinoma tissue than in plasma, and DHT is considered to be locally produced from circulating
androstenedione by
17beta-hydroxysteroid dehydrogenase type 5 and 5alpha-reductase. On the other hand,
aromatase was recently reported as a negative regulator for intratumoral DHT production by possibly reducing the precursor
testosterone.
Androgens predominantly show antiproliferative effects in
breast carcinoma cells, but association between AR status and the clinical outcome of the patient remains controversial, perhaps partly because AR status does not necessarily reflect androgenic action in
breast carcinoma. Recently, molecular apocrine
breast carcinoma was identified by microarray analysis. Molecular apocrine
carcinoma was characterized by being
estrogen receptor (ER) negative and AR positive and by being associated with increased
androgen signaling and apocrine features. Therefore, androgenic actions may also be involved in apocrine features in
breast carcinoma.