Effects of low dose tamoxifen on normal breast tissue from premenopausal women.

The aim of this study was to determine the effects of low doses of tamoxifen (5 and 10mg/day) for 50 days compared with the standard dose (20 mg/day) on breast biomarkers measured in normal breast tissue from premenopausal patients. A randomised double-blind study was performed using tissue from 56 premenopausal women with a diagnosis of fibroadenoma of the breast. Excisional biopsy was performed on the 50th day of therapy. Normal breast tissue samples were collected during surgery. The patients were divided in groups: A (placebo, n=11); group B (5 mg, n=16), group C (10 mg, n=14) and group D (20 mg, n=15). In this cross-sectional study, differences in the expression of Oestrogen Receptor alpha (ERalpha), Progesterone Receptor (PR), Ki-67, apoptotic bodies and mitotic index between the different groups after treatment can be seen on the normal breast tissue. We believe that a lower dose of tamoxifen could reduce the side-effects associated with treatment without affecting its chemopreventive activity in the breast.

Regulation of estrogen target genes and growth by selective estrogen-receptor modulators in endometrial cancer cells.

OBJECTIVE: Tamoxifen has mixed agonist/antagonist activities, leading to tissue-specific estrogen-like actions and endometrial cancer. The purpose of this study was to evaluate the effects of antiestrogens on the growth of estrogen receptor (ER)-positive ECC-1 endometrial cancer cells in vitro and in vivo. METHODS: We performed growth studies and luciferase assays using ERE-tK and AP-1 reporters. ERalpha protein expression was measured by Western blot after antiestrogen treatments. We investigated the actions of antiestrogens on the transcription of the pS2 gene in situ measured by Northern blot and the actions of antiestrogens on the VEGF protein secreted by ELISA. ERalpha, ERbeta, EGFR, and HER2/neu mRNAs were determined by RT-PCR. Last, ECC-1 tumors were developed by inoculation of cells into ovariectomized athymic mice and treated with estradiol (E2), tamoxifen, raloxifene, and a combination. RESULTS: E2 induced cell proliferation while antiestrogens did not. E2 and raloxifene down regulated ERalpha protein; in contrast, 4OHT did not. ICI182,780 completely degraded the receptor. ECC-1 cells express ERbeta at insignificant levels. Luciferase assays did not show any induction in ERE- nor AP-1-mediated transcription by antiestrogens. E2 caused a concentration-dependent increase in pS2 mRNA but antiestrogens did not. E2 increased VEGF expression in a dose-dependent manner and antiestrogens blocked E2 action. E2 down regulated HER2/neu while 4OHT and raloxifene did not change HER2/neu levels compared to control. In addition, EGFR mRNA was down regulated by E2 but raloxifene did not change it. Tamoxifen and raloxifene did not promote tumor growth in vivo. However, raloxifene (1.5 mg daily) only partially blocked E2-stimulated growth. CONCLUSION: Tamoxifen and raloxifene are antiproliferative agents and antiestrogens in ECC-1 endometrial cells in vitro and in vivo. The observation that selective estrogen-receptor modulators do not down regulate EGFR and HER2/neu mRNA may provide a potential role for these oncogenes in the development of raloxifene- or tamoxifen-stimulated endometrial cancer. The ECC-1 cell line could provide important new clues about the evolution of drug resistance to tamoxifen and raloxifene.

Modulation of estrous cycle and LH, FSH and melatonin levels by pinealectomy and sham-pinealectomy in female rats.

1. The pineal has been shown to have a role in controlling reproduction of polyestrus mammals (like humans and laboratory rodents). It influences the age of sexual maturation; the timing of the ovulatory cycle; and gonadal steroidogenesis. 2. Here the authors report the early and late effects of pinealectomy (Px) and sham-pinealectomy (SPx) on the estrous cycle periodicity, plasma LH, FSH and urinary 6-sulphatoxymelatonin (6-SMT) excretion in female rats. 3. Female Wistar rats (3-4 months of age) were maintained on 12/12 L/D cycle. Orbital venous plexus blood and urine samples were collected from the same rat during the estrus phase before surgery, 4-7 and 55-60 days post surgery. 4. Daily vaginal smears were taken to monitor the estrous cycle and they showed a time dependent increase in the estrus stage duration in Px rats (estrus stage: 1 day in control; 3-4 days after 45 days Px). 5. The decrease of gonadotropins at early post Px was due to surgical stress. 6. 6-SMT levels were significantly lower at 4-7 days post SPx, but at 55-60 d post surgery these levels returned to control values, which indicate pineal gland integrity. The reduction in urinary 6-SMT may be attributed to a possible high level of plasma corticosterone occurring after surgical manipulations. 7. 6-SMT levels in Px rats were extremely lower at 4-7 and 55-60 days post surgery, but not null, confirming the surgical removal of the pineal gland and indicating the synthesis of melatonin in sites other than the pineal gland.

A pilot study of the effects of short-term tamoxifen therapy on Ki-67 labelling index in women with primary breast cancer.

In this study we demonstrate the change in estrogen receptor (ER) level and cell proliferation in human breast cancer after a short-term tamoxifen therapy. Ten pre- and post-treatment breast tumor samples were examined immunohistochemically using ER and Ki-67 antibodies. Before tamoxifen treatment, six (60%) of ten patients were positive for ER. Tamoxifen increased the ER level in one patient and decreased the level in 4 patients. There was no significant change in ER level by tamoxifen therapy. On the other hand, Ki-67 labelling index (LI) significantly decreased after tamoxifen treatment. When Ki-67 LI was analyzed according to ER level, there was no difference between pre- and post-tamoxifen treatment in ER-negative patients, however, a significant decrease of Ki-67 LI by tamoxifen treatment was seen in ER-positive patients. Patients who showed down-regulation of ER expression tended to show a decrease of Ki-67 LI after tamoxifen therapy. In conclusion, short-term tamoxifen therapy decreased the proliferation of breast cancer, in ER-positive breast tumor samples.