Estrogen receptor in dissociated and cultured human breast fibroadenoma epithelial cells

Breast fibroadenomas are less frequent in women with uterine fibroids

BACKGROUND

The etiology and incidence of Fibroadenoma (FA) as the most frequent benign breast mass and uterine fibroma (UF) as the most benign gynecological disorders are unknown.

OBJECTIVE

Considering the dependency of FA and UF to sex hormones, our objective was to investigate the association of these two neoplasms.

METHODS

Among women attending the hospital Gynecology Clinic, those with typical uterine fibroids in their pelvic ultrasound constituted cases and those with no pathology the controls. All participants underwent breast ultrasound for FA. Criteria for diagnosis of FA were a typical image for lumps <2 cm in women aged <40 and <1 cm in ages ≥ 40, and a histologic diagnosis for all other participants or larger lumps.

RESULTS

The mean age of cases and controls was 42.4 and 41.7 years, respectively. FA were detected in 140 (23%) of all participants; 19.7% of the cases, and 26.2% of the controls (p = 0.07). FA and UF had a borderline reverse association (OR = 0.69, 95% CI = 0.46-1.02, p = 0.07).

CONCLUSION

The incidence of FA is lower in patients with UF. Further studies are needed to find the selective effects of estrogen and progesterone on hormonal receptors of these two tumors.

The effect of tamoxifen on PCNA expression in fibroadenomas

For almost three decades, tamoxifen has been used in the adjuvant treatment of breast cancer. It has also proven effective in the chemoprophylaxis of this disease and in the treatment of cyclic mastalgia. Since a fibroadenoma is a benign hormone-dependent neoplasm which contains estrogen receptor (ER) levels higher than in the mammary lobule, an evaluation of the effect of this drug on the proliferative activity of both the epithelium and the stroma of fibroadenomas in premenopausal women following the administration of 10 or 20 mg/day over 22 days was proposed. Forty women with fibroadenoma were selected for a randomized double-blind trial. They had regular menstrual cycles and had received neither hormones nor become pregnant 12 months prior to this study. Patients were divided into three groups: A (n = 14; placebo), B (n = 13; tamoxifen 10 mg/day), and C (n = 13; tamoxifen 20 mg/day). The treatment was initiated on the first day of their menstrual cycle and the surgeries were performed on the 22nd day. Estradiol, progesterone, and steroid hormone binding globulin (SHBG) were measured twice. The first measurement was performed on the 22nd day of the previous menstrual cycle and the second one was performed on the day of surgery. The fibroadenoma was fixed in 10% formaldehyde solution and stained with hematoxylin and eosin and then processed through immunohistochemical reaction (PC-10, DAKO code number M879, Denmark A/S). The immunoexpression of the proliferative cell nuclear antigen (PCNA) of at least 500 epithelial and 500 stromal cells was evaluated. Such cells were interactively counted using the Kontron Imaging System KS-300 computerized analysis system, with x 400 magnification. As to PCNA expression in the fibroadenomas' epithelium, the average percentage of stained nuclei in groups A, B, and C was 25.2, 19.3, and 18.0, respectively. However, no significant difference was found in the variance analysis of these data (p = 0.168). As to the study of the fibroadenomas' stroma, the average percentage of stained nuclei found in groups A, B, and C was 32.4, 23.2, and 18.4, respectively. The variance analysis (p = 0.031) and Fisher's multiple comparison test (1.39; 26.67 confidence interval [CI]) confirmed that the number of PCNA-expressing nuclei in the stroma was significantly lower in group C (20 mg/day) compared to group A (control). However, there was no significant difference between group B (10 mg/day) and group C (20 mg/day). It was found that tamoxifen reduced the expression of PCNA in the epithelium and the stroma of the fibroadenoma. However, the effect was only statistically significant in the stroma when a 20 mg/day dose was administered.

Expression of the estrogen receptor gene in developing and adult human breast

Although studies of the estrogen receptor gene abound in rodent models and breast cancer cell lines, little is known about expression of this gene in normal human breast. Information regarding the physiology of this gene's expression is important if we are to elucidate abnormalities of the gene that may be involved in breast carcinogenesis. We evaluated levels of mRNA expression of the estrogen receptor (ER) gene and its protein product in a set of 89 breasts from clinically normal female infants, children, adolescents, and adult premenopausal and post-menopausal women. mRNA expression of the gene varied with the hormonal status. Relatively higher levels of gene transcripts were found in breasts of peri-menarchal girls, women in the luteal phase of the menstrual cycle, and in those with fibrocystic change. Higher levels were also occasionally found in breasts of infants and in most pre-adolescent children. Lower levels were seen in breasts of women in the follicular phase of the menstrual cycle, during pregnancy, and after menopause. Nuclear protein staining was common in breasts of normal children and peri-menarchal adolescents, and in post-menopausal atrophic breasts. Nuclear ER protein was infrequently detected in reproductive aged women's breasts, but was more often seen in follicular than in luteal menstrual phase or pregnant breast. ER protein was more frequently seen in post-menopausal than in pre-menopausal breasts with fibrocystic change. The results fit a model in which circulating levels of estrogen are inversely related to levels of mRNA transcribed from the estrogen receptor gene in normal physiologic states. Abnormally high levels of gene transcription may occur in some cases of fibrocystic change.

Steroid hormones and risk of breast cancer

BACKGROUND

More than three decades of epidemiologic studies have identified numerous risk factors for breast cancer. These factors have been estimated to account for only 20-25% of disease occurrence. However, among these factors, several are related to sex steroid hormones: sex of the affected individuals (women), early age of menarche and late age of menopause, parity, late age at first pregnancy, and obesity in postmenopausal women.

METHODS

Theoretical models and laboratory data support hormonal mechanisms of carcinogenesis, particularly as they relate to proliferation of breast ductal epithelium and terminal end bud growth and differentiation in the lobules of the breast. The recent introduction of biologic markers and molecular epidemiology allows for studies that use laboratory technology in the context of epidemiologic research.

RESULTS

This paper summarizes the epidemiologic literature on exogenous hormones, addresses the issue of endogenous steroid hormone levels and estrogen metabolism in serum and breast tissue in premenopausal and postmenopausal women with and without cancer, speaks to the cellular mechanisms of action of estrogen and progesterone, and highlights some of the biologic markers relevant to studies of breast cancer and precursor lesions, with particular emphasis on those that may be hormonally induced or altered.

CONCLUSIONS

These markers must be better defined in terms of breast cancer pathogenesis. Studies are needed to evaluate the direct effects of behavioral/environmental risk factors on relevant biomarkers as well as to assess the interactions of epidemiologic factors and biomarkers on risk of breast cancer.

Hormonal carcinogenesis in breast cancer: cellular and molecular studies of malignant progression

We have established and characterized a series of variant cell lines in which to identify the critical factors associated with E2-induced malignant progression, and the acquisition to tamoxifen resistance in human breast cancer. Sublines of the hormone-dependent MCF-7 cell line (MCF7/MIII and MCF7/LCC1) form stable, invasive, estrogen independent tumors in the mammary fat pads of ovariectomized athymic nude mice. These cells retain expression of both estrogen (ER) and progesterone receptors (PGR), but retain sensitivity to each of the major structural classes of antiestrogens. The tamoxifen-resistant MCF7/LCC2 cells retain sensitivity to the inhibitory effects of the steroidal antiestrogen ICI 182780. By comparing the parental hormone-dependent and variant hormone-independent cells, we have demonstrated an altered expression of some estrogen regulated genes (PGR, pS2, cathepsin D) in the hormone-independent variants. Other genes remain normally estrogen regulated (ER, laminin receptor, EGF-receptor). These data strongly implicate the altered regulation of a specific subset or network of estrogen regulated genes in the malignant progression of human breast cancer. Some of the primary response genes in this network may exhibit dose-response and induction kinetics similar to pS2, which is constitutively upregulated in the MCF7/MIII, MCF7/LCC1 and MCF7/LCC2 cells.

Effects of estrogen, epidermal growth factor, and transforming growth factor-alpha on the growth of human breast epithelial cells in primary culture

Since 17 beta-estradiol (E2)-stimulated growth in human breast cancer cell lines has been shown to be accompanied by increased production of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) and their receptor, we investigated the effects of E2 and these growth factors on the growth of human breast epithelial cells (HBEC) in primary culture. HBEC from normal, benign, and malignant tissues were cultured in serum-free medium [DME:F12(1:1), 5 mg/ml BSA, 10 ng/ml cholera toxin, 0.5 micrograms/ml cortisol, 10 micrograms/ml insulin] in the presence and absence of E2, EGF, and TGF-alpha. Tritiated-thymidine ([3H]TdR) incorporation into DNA was used as a measure of cell growth. E2 did not stimulate growth of any of the cultures at all concentrations examined (10(-9) to 10(-6) M). In contrast, EGF ranging from 1 to 100 ng/ml consistently increased the growth of cells of all three breast tissue types in a dose-dependent manner. The EGF stimulation was inhibited by MAb 528, a monoclonal antibody against the EGF receptor. TGF-alpha was equally or more effective in stimulating proliferation, although its dose-response range was different than that of EGF. E2 and EGF together acted in a synergistic manner in 50% of the samples examined. These studies suggest that E2 can exert effects on HBEC growth via modulation of the cells' response to EGF.

Biotransformation of estradiol by explant culture of human mammary tissue

In vivo experiments on strains of mice that differ in the risk of developing mammary cancer have demonstrated a correlation between the extent of 16 alpha-hydroxylation of estradiol and incidence of mammary cancer. The ability of human mammary terminal duct lobular unit (TDLU), the site of neoplastic transformation, to metabolize estradiol or to accumulate estradiol metabolites has not been unequivocally established. Using a newly developed human mammary TDLU explant culture system and a radiometric assay for estradiol metabolism, we compared the site-specific metabolism of estradiol by the 17-oxidation, 2-hydroxylation, and 16 alpha-hydroxylation pathways in noninvolved human mammary tissue. The relative extent of estradiol 16 alpha-hydroxylation was found to be increased in TDLU from patients in the luteal phase of the menstrual cycle in relation to either those from patients in the follicular phase or from postmenopausal subjects. This study demonstrates that TDLU can metabolize estradiol extrahepatically and that 16 alpha-hydroxylation in the target tissue is dependent on the phase of the menstrual cycle. Furthermore, the specific, risk-related increase in 16 alpha-hydroxylation suggests that intrinsic metabolic ability of the target tissue leading to the formation of 16 alpha-hydroxyestrone from estradiol may be a determinant in, or a marker for, the relative risk of developing mammary cancer.

Routine culturing of normal, dysplastic and malignant human mammary epithelial cells from small tissue samples

We compared the growth and morphology of normal, dysplastic and malignant human mammary epithelial cells (HMEC) in medium containing 5% human serum, a serum-free medium (32) and serum-free medium with a low Ca++ concentration. Tissues were dissociated and epithelial organoids or single cells were seeded onto collagen-coated dishes. The cells grew in serum-containing medium, but growth of fibroblasts was also stimulated. The serum-free medium consistently selected for and stimulated the growth of epithelial cells. There was little advantage in reducing the Ca++ concentration to further increase cell yield. This serum-free primary culture system allows us to routinely produce sufficient numbers of HMEC from small tissue samples for molecular biological investigations. Furthermore, the maintenance of cells in a defined medium can provide a system for evaluating the direct effects of factors on gene expression.

Fibroadenoma

The common breast fibroadenoma makes up between one-third and one-half of biopsies for benign breast disease. The contemporary view is that it is an abnormality of normal development and involution rather than a neoplasm. Various other benign conditions may be clinically indistinguishable, and histological confirmation was only obtained in 68% of 321 masses thought to be fibroadenomas. Short-term (13-24 mo) follow-up of 201 masses, thought to be fibroadenomas on clinical and cytological grounds, showed resolution in 31% and regression in a further 12%, this behavior being more common with single lesions; a further 32% increased in size. There have been no long-term studies, but it is likely that most regress toward the end of a woman's reproductive years. Aspiration cytology can differentiate malignant from benign disease with great accuracy, but had impaired sensitivity (87%) and specificity (76%) in differentiating fibroadenoma from other benign processes in an analysis of 244 successful aspirates. While these lesions may be safely left in women under 25 years of age, only 19 (27%) of 70 women of this age group chose this option and excision remains the most frequent treatment.