Expression of the androgen receptor and syndecan-1 in breast tissue during different hormonal treatments in cynomolgus monkeys

Objectives To analyze the expression of the androgen receptor(AR) and syndecan-1 in breast tissue during long-term hormonal treatment in cynomolgus monkeys. Methods Sixty oophorectomized macaques were randomized to receive either tibolone, conjugated equine estrogens (CEE), CEE + medroxyprogesterone acetate (MPA) or no hormonal treatment. Breast tissue was collected at necropsy after 2 years and stained for AR and syndecan-1. Results Apparent differences were seen between treatment groups as compared to untreated animals. AR expression was markedly increased by tibolone and suppressed by combined CEE/MPA. Both treatments increased syndecan-1 in stromal tissue, whereas CEE alone had no significant effect. Conclusions We found alternative regimens for hormonal therapy to differ in their influence on two markers of importance for the development of breast cancer. The results may be relevant for the ongoing clinical discussion on the long-term safety of different hormonal treatments.