Conner Peter, Register Tom C, Skoog Lambert, Tani Edneia, von Schoultz Bo, Cline J Mark
Department of Obstetrics, Karolinska Hospital, Stockholm, Sweden and Comparative Medicine Clinical Research Center, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
Am J Obstet Gynecol. 2005 Jul;193(1):58-63. doi: 10.1016/j.ajog.2004.11.056.
The purpose of this study was to analyze the expression of p53 and markers for apoptosis in breast tissue during long-term hormone therapy in cynomolgus monkeys.
Sixty oophorectomized macaques were randomized to receive 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 p53, p21, and cleaved caspase-3.
Differences were seen between treatment groups. The expression of p53 and caspase-3 was significantly lower in tibolone-treated animals (P<.01). Levels of p53 and caspase-3 were lower in the combined treatment group (CEE+MPA) when compared to both estrogen only and control groups.
Alternative regimens for hormonal therapy seem to have different effects on p53 expression and apoptotic activity within the breast. A combined effect of increased proliferation and decreased apoptosis could be one possible mechanism to explain an increased risk for breast cancer.
