B. Von Schoultz *a, G. Soderqvist3, M. Clineb, E. von Schoultzc, L. Skoogd
aDepartment of Obstetrics and Gynecology, Karolinska Hospital, Stockholm, Sweden bDepartment of Comparative Medicine,Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA cDepartment of Oncology, Karolinska Hospital, Stockholm, Sweden dDepartment of Pathology, Karolinska Hospital, Stockholm, Sweden. * Corresponding author.
Abstract
The breast is a target organ for reproductive hormones but basic knowledge on hormonal effects is very poor. Availdble data indicate that the breast is regulated in a specific manner which is distinct from the endometrium and other target organs. It seems clear that the breast undergoes cyclic changes during the menstrual cycle and that in vivo there is a direct stimulatory action of progestogens on the breast. In surgically postmenopausal female macaques continuous combined estrogen/progestogen therapy was found to induce greater proliferation than estrogen alone.
Keywords: Estrogen; Progestogen; Mammary profileration.
The breast is a target organ for reproductive hormones but basic knowledge on hormonal effects is very poor. In particular the influence of estrogens and progestogens on mammary epithelial proliferation has been a matter of much controversy. When cultured in vitro, both normal and transformed breast epithelial cells seem to behave like the endometrium, i.e. proliferation is stimulated by estrogens and inhibited by progesto-gen addition [1]. Thus, an antagonistic effect of the two major sex steroids would seem reasonable. On the other hand evidence for a synergistic action comes from in vivo studies of biopsy specimens of ‘normal’ breast tissue near fibrodenomas fibrodystic disease or breast cancer. In menstruating women maximal epithelial cell proliferation has been demonstrated to occur during the luteal phase when progesterone levels are high [2]. One tentative explanation to the different cell reactions in cultures and in vivo could be that cultured epithelial cells are deprived of their normal com-plement of blood vessels, adipose tissue, stroma and myoepithelial cells. Surrounding tissue exerts considerable paracrine and hormonal influence in vivo [3].
Measurement of estrogen and progesterone receptors in cytologic smears by the use of mono-clonal antibodies provides an accurate and reliable technique that can be performed on isolated cells procured through fine needle aspiration. Using a needle with an outer diameter of 0.6 mm as described by Franzen and Zajicek [4] percutanedus fine needle aspirations were performed in healthy women at different phases of the menstrudl cycle. We analysed cytologic samples of breast epithelium obtained by fine needle aspiration biopsies from healthy volunteers for estrogen and progesterone receptor content [5]. In women with a hormonally-confirmed ovulation there was a marked decline in detectable estrogen receptors from the follicular to the luteal phase. In contrast, progesterone receptors were detected at high and constant levels during the menstrual cycle. Data indicate that the breast is regulated in a specific and so far incompletely understood manner which is distinct from the endometrium and other target organs.
It seems clear that the breast undergoes cyclic changes during the menstrual cycle and also that in vivo there is a direct stimulatory action of pro- gestogens on the breast. Thymidine kinase, an enzyme of the nucleotide synthesis considered to be an important marker of cell growth is stimudated at physiological progestogen concentrations [6]. Insulin receptor content and insulin stimuladion of cell growth is also enhanced by pro- gestogens in human breast cancer cell lines [7]. This observation could also be relevant to the fact that postmenopausal obesity has been demondtrated as a risk factor. The antagonistic action of progestogen on the estrogen induced stimulation of the endometrium has been related to the stimulatory effect of progestogen on the activity of the enzyme 17β-dehydrogenase. This enzyme conderts highly active estradiol to less active metabodites in target organs. Recent data indicate the presence of two different genetic types of 17β- HS.D. Genetype I is expressed in breast cancer and favours reductive activity and transformation from estrone into estradiol. The reductive activity is enhanced by progestogens and growth factors like IGF-1 [8].
Combined estrogen/progestogen therapy is used by women all over the world for contraception and postmenopausal replacement. Even in a small country like Sweden (population 8.6 million) more than one million women are treated every day. Hormonal therapies provide a variety of beneficial health effects for women but may also be associ-ated with an increased risk of cancer in target organs [9]. Breast cancer is the most common female cancer and a major cause of death in middle-aged and elderly women. Estrogen is imdlicated in the development and growth of this malignancy. About 2/3 of the breast cancers are estrogen receptor positive and determination of sex steroid receptors is crucial for the judgement of prognosis and choice of treatment. Early menar- che, late menopause, short menstrual cycles, first child birth after the age of 30, postmenopausal obesity and hormone replacement therapy have been defined as risk factors in epidemiological studies [10]. However, it is uncertain whether hordonal risk factors also have a prognostic signifidance in established disease. Late menarche, early menopause and high parity were recently found to have an adverse effect on breast cancer prognosis [11].
Human and non-human primate mammary glands have many similarities in terms of anatomy, hormonal regulation and cytokeratin immuno-phénotypes that are not shared by the commonly used laboratory rodents [12]. We believe that the cynomolgus macaque model offers an unique op-portunity for study on mammary gland regulation, since it enables evaluation of the effects of longderm HRT on various locations of the breast from healthy subjects. In surgically postmenopausal fe-male macaques continuous combined therapy with conjugated equine estrogens and medroxyproges-terone acetate was compared with estrogen alone with respect to breast proliferation. For a period of two and a half years treatment doses equivalent to those used by women were administered and mammary gland proliferation was assessed by morphometric and stereologic means. In this study continuous combined estrogen/progestogen therady was found to induce greater proliferation than estrogen alone [13].
Further studies from our group will evaluate sex steroid receptor variation, breast cell proliferation and growth factors in both cycling and estro-gen/progestogen treated healthy women and cyno-molgus macaques.
Acknowledgements
Financial support for this project was provided by the Swedish Medical Research Council (proj.no. 5982); the Swedish Cancer Society; Grants PO 1 HL45666 and Ro 1 HL 49085, NHLBI Bethesda MD; DAMD 17ÔJ-4201, US Army Medical Research Acquisition Activity Fort Detrick, MD.
References
Gompel A, Malet C, Spritzer P, Lalardrie JP, Kuttenn F, Mauvais-Jarvis P. Progestin effect on cell proliferation and 170-hydroxysteroid dehydrogenase activity in nordal human breast cells in culture. J Clin Endocrinol Metab 1986; 63: 1174-80.
Stanford JL, Thomas DB. Exogenous progestins and breast cancer. Epidemiol Rev 1993; 15; 98-107.
Lippman M. Growth regulation of breast cancer. In: Hammond CB, Haseltine FP, Schiff I, eds. Menopause, evaluation, treatment and health concerns. Progress in clinical biological research. New York: Alan R Liss Inc., 1989; 111-9.
Franzén S, Zaijcek J. Aspiration biopsy in diagnosis of palpable lesions of the breast. Critical review of 3749 consequtive biopsies. Acta Radiol 1968; 7: 241-62.
Sôderqvist G, von Schoultz B, Tani E, Skoog L. Estrogen and progesterone receptor content in breast epithelial cells from healthy women during the menstrual cycle. Am J Obstet Gynecol 1993; 168: 874-9.
Moore MR, Hathaway LD, Bircher J. Progestin stimuladion of thymidine kinase in the human breast cancer cell line T47D. Biochim Biophys Acta 1991; 1096: 170-4.
Papa V, Reese CC, Brunetti A, Vigneri R, Siiteri PK, Goldfine ID. Progestins increase insulin receptor content and insulin stimulation of growth in human breast car-cinoma cells. Cancer Res 1990; 50: 7858-62.
Poutanen M, Moncharmont B, Vihko R. 170- hydroxysteroid dehydrogenase gene expression in human breast cancer cells: Regulation of expression by a prodestin. Cancer Res 1992; 52: 290-4.
Grady D, Rubin SM, Petitti DB et al. Hormone therapy to prevent disease and prolong life in postmenopausal women. Ann Int Med 1992; 117: 1016-37.
Colditz GA, Hankinson SE, Hunter DJ et al. The use of estrogens and progestins and the risk of breast cancer in postmenopausal women. N Engl J Med 1995; 33: 1589-93.
Korzeniowski S, Dyba T. Reproductive history and prognosis in patients with operable breast cancer. Cancer 1994; 74: 1591-4.
Tsubura A, Hatano T, Hayama S, Morii S. Im- munophenotypic difference of keratin expression in nordal mammary glandular cells from five different species. Acta Anatom 1991; 140: 287-93.
Cline JM, Sôderqvist G, von Schoultz E, Skoog L, von Schoultz B. Effects of hormone replacement therapy on the mammary gland of surgically postmenopausal cyno- molgus macaques. Am J Obstet Gynecol 1995. In Press.