It is well-known that
estrogens are closely involved in the growth of human
breast carcinomas, and that the great majority of
breast carcinoma express
estrogen receptors. Recent studies have demonstrated that
estrogens are locally produced and act on the
breast carcinoma tissue. Among these pathways,
aromatase is a key
enzyme for intratumoral production of
estrogens in
breast carcinomas, and
aromatase inhibitors are currently used in the
breast carcinoma in postmenopausal women as an
estrogen deprivation
therapy. This review summarizes the results of recent studies on the expression and regulation of
aromatase in
breast carcinoma tissues, and discusses the potential
biological and/or clinical significance of
aromatase.
Aromatase is abundantly expressed in various cell types, such as
carcinoma cells, intratumoral stromal cells, and adipocytes adjacent to the
carcinoma, in
breast carcinoma tissues. Further, a key regulator for
aromatase expression differed according to cell type. In addition,
aromatase suppressed in situ production of bioactive
androgen, 5alpha-dihydrotestosterone (DHT), in
breast carcinoma.
Aromatase inhibitors may thus have additional antiproliferative effects through increasing local DHT concentration with
estrogen deprivation.