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.

Effects of the new selective estrogen receptor modulator LY353381.HCl (Arzoxifene) on human endometrial cancer growth in athymic mice

PURPOSE

Arzoxifene (Arzox) is a novel benzothiophene analogue with selective estrogen receptor modulator activity similar to raloxifene. Arzox is being developed as a treatment for breast cancer and has a predominantly antiestrogenic effect on the rodent uterus. Our objectives were to verify whether the novel selective estrogen receptor modulator, Arzox, can be a good first-line agent and also be effective at controlling the growth of endometrial cancer after exposure to tamoxifen (Tam).

EXPERIMENTAL DESIGN

We compared the effects of Tam and Arzox on the growth of estrogen responsive ECC-1 endometrial cancer cells in vitro, and we determined their antitumor effects on ECC-1 and EnCa101 endometrial carcinoma growth in athymic mice.

RESULTS

We observed that estrogen receptor protein expression is down-regulated by Arzox to the same extent as raloxifene, whereas 4-hydroxytamoxifen, the active metabolite of Tam, does not affect estrogen receptor protein levels. Tam and Arzox inhibit the growth of Tam-naïve ECC-1 tumors in athymic mice. However when Tam-stimulated or estrogen-stimulated (which had been treated with Tam previously) EnCa101 endometrial tumors were treated with Tam or Arzox, we observed a stimulatory effect of both compounds in these models.

CONCLUSIONS

The results indicate that Arzox may be a good first-line agent, but it may be ineffective at controlling the growth of endometrial cancer after exposure to Tam. Our data suggest that Arzox stimulates endometrial tumor growth to at least the same extent as Tam, thereby suggesting a limited role as a second-line agent for the patient on Tam who develops occult endometrial cancer.

Analysis of cross-resistance of the selective estrogen receptor modulators arzoxifene (LY353381) and LY117018 in tamoxifen-stimulated breast cancer xenografts

PURPOSE

Cross-resistance is the primary issue facing the evaluation of new antiestrogens to treat metastatic breast cancer because they may be tested, initially, in populations of patients that have failed long-term adjuvant tamoxifen (Tam) therapy.

EXPERIMENTAL DESIGN

We have tested the benzothiophene derivatives, arzoxifene (Arzox; LY353381) and LY117018 in two models of Tam-stimulated tumor growth derived from either MCF-7 (M. M. Gottardis and V. C. Jordan, Cancer Res., 48: 5183-5187, 1988) or T47D (J. MacGregor Schafer et al., Clin. Cancer Res., 6: 4373-4380, 2000) breast cancer cells.

RESULTS

Using the MCF-7:Tam model, we found that both Arzox and LY117018 (1.5 mg/day) resulted in tumor growth and, therefore, were partially cross-resistant with Tam. Next, using the T47D:17beta-estradiol (E(2)) model, we compared the antiestrogenic/antitumor properties of Arzox and LY117018 and determined that neither Arzox nor LY117018 caused T47D:E(2) tumor growth after 21 weeks. In addition, we determined that long-term treatment does not result in failure and subsequent development of transplantable Arzox- or LY117018-stimulated tumors. To establish whether Arzox and LY117018 are cross-resistant in T47D:Tam tumors, mice were treated with Arzox or LY117018 (1.5 mg/day), and, again, we found that neither resulted in the growth of transplantable tumors. Lastly, we showed that Arzox and LY117018 were only partially able to compete with postmenopausal E(2) (0.3 cm silastic capsule) in T47D:Tam tumors. However, when T47D:E(2) tumors were treated for 7 days instead of 5 days, both Arzox and LY117018 were more effective.

CONCLUSIONS

Arzox is not cross-resistant with Tam in the T47D athymic mouse model but does exhibit cross-resistance in the MCF-7 model.

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.

Novel agents to modulate oestrogen action

As women enter the menopause, the majority suffers symptoms associated with a dramatic fall in circulating levels of 17 beta-oestradiol and oestrone. As a result, the oestrogen protective effect against coronary artery disease and osteoporosis is lost. To solve these problems, hormone replacement therapy is often used. However, there are a number of side-effects including increased risk from breast and uterine cancer that can limit compliance. New drugs, called selective oestrogen modulators (SERMs), have been developed to mimic oestrogen's effects on the liver, heart and bones but without its harmful effects on the breast and uterus. SERMs are structurally diverse compounds that bind to oestrogen receptors and elicit agonist or antagonist responses depending on the target tissue and hormonal milieu. The drugs are being used, or evaluated, for the prevention of hormone-responsive breast cancer, osteoporosis and cardiovascular disease in postmenopausal women. Tamoxifen is the endocrine treatment of choice for breast cancer, but it also has beneficial effects on bone density and serum lipids in postmenopausal women. Recently, tamoxifen was shown to decrease the risk of invasive breast cancer in women at high risk. However, tamoxifen has some stimulatory effects on the endometrium. Raloxifene is used to prevent osteoporosis and fractures. Raloxifene also lowers circulating cholesterol and the incidence of invasive breast cancer in postmenopausal women but does not stimulate the endometrium. The SERMs have evolved from mere laboratory curiosities into drugs that hold promise for preventing several major diseases associated with ageing in women.