Mammary tissue samples were collected from 32 healthy post menopausal women: 19 were using estrogen and progestagen on a cyclical schedule (conjugated estrogens, 0.625mg, for 21 days/month, associated to medroxyprogesterone acetate, 5mg, for the last 12 days) and 13 were using estrogen-only, on a 21 days/month schedule (conjugated estrogens, 0.625mg), all during 6 consecutive months. Biopsies were performed on the external left-hand upper quadrant before and after 6 months of treatment. Immunohystochemical analysis was performed with the antibodies: anti-PCNA of the PC-10 type, anti KI-67 of the MIB-1 type, anti ER (Estrogen Receptor) of the 1-D5 type and anti-PR (Progesterone Receptor) of the 1-A6 type. No significant differences were observed for the mediation factors in the group using the cyclical schedule (ER: P = 0.326; PR: P = 0.228). In the estrogen-only group, a P value near the statistical probability limit was found for the PR (P = 0.053) but not for ER (P = 0.203). No significant statistical difference was found for the cellular proliferation factor PCNA in both treatment groups (cyclical schedule: P = 0.121; estrogen-only schedule: P = 0.208). However, there was a trend in the estrogen-only group for Ki-67 (P = 0.084) but not in the cyclical schedule group (P = 0.776). These results suggest that progestagen association to estrogen therapy in this sample of postmenopausal women may have contributed to a possible reduction in the progesterone receptor expression and cellular proliferation, when estimated by Ki-67 marker, like a moderator factor to cellular proliferation. New studies are necessary to confirm this hypothesis.
Menopause; Steroid receptors; PCNA; Ki-67; Breast
