Objectives: To investigate the effect of hormone therapy (HT) on the expression of hormone receptors and the ex vivo estrogen biosynthesis in the breast.
Methods: Comparative studies were carried out in breast tissue from 28 postmenopausal women undergoing breast surgery due to breast cancer (BC). Glandular breast tissue at least 1cm distant from the tumor was analyzed. Groups included patients having received HT (n=18), and non-user of HT (controls, n=10) prior to BC diagnosis. Steroid sulfatase (STS) activity was evaluated by incubating homogenized breast tissue with [3H]-estrone sulfate. Thin layer chromatography was performed to separate the products estrone (E1) and estradiol (E2). Histomorphometry for breast tissue composition and immunohistochemistry for expression of estrogen receptor (ER) alpha and beta as well as progesterone receptor (PR) were performed.
Results: In all groups, significantly more E2 than E1 was produced. Local E2 formation was higher in women having been treated with estrogen and progestogen (p< or =0.05). Local EZ formation was positively correlated with ER alpha expression (r(s)=0.5; p=0.03). Histomorphometrical and immunohistochemical outcomes did not differ between groups. However, the amount of vessels was higher in women having been treated with HT compared to controls (p=0.09).
Conclusions: Long-term HT increases local estrogen formation in normal human breast tissue.