Path. Res. Pract. 187, 584-586 (1991)
Effects of Estrogens on Pituitary Cell and Pituitary Tumor Growth R. V. Lloyd, L. Jin, K. Fields and E. Kulig Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA
SUMMARY
Estrogens have been known to induce PRL cell hyperplasia in the anterior pituitary of some species for many decades. Recent studies have shown variable susceptibility to. estrogen-induced hyperplasia in different strains of rats. The distinction between hyperplastic pituitaries and adenomas is usually not made by most investigators in this field, although true neoplasms can usually be propagated by serial transplantation. The growth of transplantable tumors is usually inhibited by estrogen in vivo. Estrogens have a biphasic effect on pituitary cell proliferation in vitro with higher concentrations of estradiol inhibit cell growth, and lower concentrations stimulating PRL secretion. Estrogens can regulate PRL gene methylation in vivo thus affecting PRL mRNA expression. Recent studies have suggested that estrogen regulates signal transduction by stimulating protein kinase C. Estrogens also regulate specific proto-oncogenes such as c-myc and c-fos. These observations may help to explain some of the regulatory effects of estrogens on cell proliferation and tumor development.
Introduction The effects of estrogens in causing anterior pituitary gland hyperplasia were reported by various investigators in 19363,5,13,21,22,24,30. Although these lesions were described as tumors, the development of transplantable pituitary tumors with chronic estrogen treatment was reported two decades later by Furth and his colleagues912
Estrogen-Induced Pituitary Hyperplasia The report of estrogen induced pituitary gland hyperplasia by six different investigators in the same year was somewhat unusual, but probably reflected the recent availability of estrogenic hormones at that time. Subsequent studies by other investigators on the cytology of estrogen-induced hyperplasia of the pituitary gland documented that the acidophilic cells were involved in this
proliferation. The careful studies of Clifton and Meyer4 showed that there was division and degranulation of 0344-0338/91/0187-0584$3.50/0
acidophils and division of chromophobic cells as well as hypersecretion of prolactin. These investigators arbitrarily defined enlarged anterior pituitaries of 30 mg or greater as tumors. This definition has been adopted by subsequent investigators. Extensive biochemical and ultrastructural studies were done on these pituitaries6 • Wiklund and co-workers showed that some strains of rats such as Fisher were more susceptible to pituitary hyperplasia than Holtzman rats 29 • These investigators documented the stimulation of PRL protein in these hyperplastic lesions. The report of Lloyd 16 showed that these enlarged pituitaries up to 150 mg were hyperplastic lesions with mixtures of various cell types and not true neoplasms. Some of the effects of estrogens on pituitary hyperplasia may be explained by changes in the arterial vasculature in the hypothalamic-pituitary region 8• Furth and his colleagues established various lines of estrogen-induced transplantable tumors after chronic treatment with estrogens9- 12 • To analyze the transition between pituitary hyperplasia
and development of transplantable tumors, Lloyd et al. 20 used dimethylbenz(a)anthracene (DMBA) and estrogen to © 1991 by Gustav Fischer Verlag, Stuttgart
Estrogens and Tumor Growth· 585
establish a transplantable pituitary cell line in Fischer 344 rats in about six months. The tumors grew readily after subcutaneous implantation and progressed from highly differentiated cells with abundant PRL hormone and mRNA production to poorly differentiated cells with serial transplant generations 2o .
ment probably involves a vast regulatory network at the level of signal transduction and proto-oncogene activation.
References
Effects of Estrogens on Transplantable and other Pituitary Tumors Although Furth et al. observed that estrogens inhibited growth of transplantable pituitary tumors, the first detailed documentation of this effect was reported by Morel et a/.2,23,27 in F 344 rats with MtTIF 4 tumors. Lloyd et at. reported similar findings in W/Fu rats with MtTIW 15 tumors 17,19. In both of these models the pituitary gland underwent PRL cell hyperplasia while growth of the transplantable tumor was inhibited. In the MtTIW 15 tumor there was inhibition of PRL production by the tumor with inhibition of tumor growth while PRL production was increased in the MtT/F 4 animals. The work of Amara and Dannies showed that estrogens had a biphasic effect on growth and on hormone expression of GH cells in vitro. Concentrations of 2 X 10- 11 M estradiol stimulated GH4C1 pituitary cells while concentrations of 3 X 10- 11 to 10- 9 M inhibited cell proliferation but stimulated PRL synthesis 1. Subsequent work by these same investigators showed that estrogens could induce differentiation in GH4C1 cells in vitro with increased numbers of secretory granules 25 . Similar findings in vivo were reported by Lloyd et al. in the DMBA-E2 induced tumor cellline2o .
Other Effects of Estrogens on Anterior Pituitary Cells Estrogens have other significant effects on pituitary cells. Dopamine D2 receptor proteins are down-regulated by estrogens 18 while the estrogen receptor protein mRNA is up-regulated by estrogen treatment26 . Recent studies in our laboratory have shown that estrogens regulate PRL DNA methylation in normal pituitary and in transplantable pituitary tumors 15 . These studies showed that in normal pituitary, MtT/F 4 and the DMBA tumors which had increased PRL mRNA expression after estrogen treatment, the PRL gene was hypomethylated. However, in the MtTlW 15 tumor which had decreased PRL expression after estrogen treatment the PRL gene was hypermethylated which correlated with the gene activity. These findings indicate that estrogens influence methylation of the PRL gene in various pituitary tissues. Estrogens have been shown to have a regulatory effect on various proto-oncogene expressions in tissues such as the hypothalamus and uterus 14,28. Estrogen regulation of c-fos and c-myc genes has been reported. In addition, protein kinase-C expression appears to be regulated by estrogens in rat pituitary tissues 7. These findings indicate that the mechanism of action of estrogens leading to pituitary cell hyperplasia and subsequent tumor develop-
1 Amara JF, Dannies PS (1983) 17~-estradiol has a biphasic effect on GH cell growth. Endocrinology 112: 1141-1143 2 AndreJ, Marchisio AM, Morel Y, Collu R (1982) Dopamine receptors in the rat pituitary and the transplantable pituitary tumor MtT/F 4: effect of chronic treatment with oestradiol. Biochem Biophys Res Commun 106: 229-235 3 Burrows H (1936) Pituitary hyperplasia in a male mouse after the administration of oestrin. Am J Cancer 28: 741-745 4 Clifton KH, Meyer RK (1956) Mechanism of anterior pituitary tumor induction by estrogen. Anat Rec 125: 65-81 5 Cramer W, Horning ES (1936) Experimental production by oestrin of pituitary tumors with hypopituitarism. Lancet i: 247-249 6 De Nicola AF Von Lawzewitsch I, Kaplan SE, Libertun C (1978) Biochemical and ultrastructural studies on estrogeninduced pituitary tumors in F 344 rats. J Natl Cancer Inst 61: 753-763 7 Drouva SV, Gorenne I, Laplante E, Rerat E, Enjalbert A, Kordon C (1990) Estradiol modulates protein kinase-C activity in the rat pituitary in vivo and in vitro. Endocrinology 126: 536-544 8 Elias KA, Weiner RI (1984) Direct arterial vascularization of estrogen-induced prolactin-secreting anterior pituitary tumors. Proc Natl Acad Sci USA 81: 4549-4553 9 Furth J and Clifton KH (1986) Experimental pituitary tumors. In: Harris G, Donovan B (Eds.) The Pituitary Glands, Vol 2: 460-497, Butterworths, London 10 Furth J, Clifton KH, Gadsen EL, Buffet RF (1956) Dependent and autonomous mammotropic pituitary tumors in rats; their somatotropic features. Cancer Res 16: 608-616 11 Furth J, Ueda G, Clifton KH (1973) The pathophysiology of pituitaries and their tumors: Methodological advances. In: Bush H (Ed) Methods in Cancer Research, Academic Press, Vol X: 201-277, New York 12 Furth J, Nakane PK, Pasteels JL (1976) Tumours of the pituitary gland. In: Turusov VS (Ed) Pathology of Tumours in Laboratory Animals, Vol I: 201-237. Tumours of the Rat, Part 2 (IARC Scientific Publications No 6), International Agency for Research on Cancer, Lyon 13 Gardner WV, Smith GM, Strong LC (1936) An observation of primary tumors of the pituitary ovaries and mammary glands in the mouse. Am J Cancer 26: 541-547 14 Insel TR (1990) Regional induction of c-(os like protein in rat brain after estradiol administration. Endocrinology 126: 1849-1853 15 Kulig FS, Landefeld TD, Lloyd RV (1990) Estrogen regulates prolactin gene methylation in transplantable rat pituitary tumor. The Endocrine Society 72nd Annual Meeting Atlanta, Georgia June 20-23. Abstract 1320, p. 354 16 Lloyd RV (1983) Estrogen-induced hyperplasia and neoplasia in the rat anterior pituitary gland. An immunohistochemical study. Am J Pathol 113: 198-206 17 Lloyd RV, Landefeld TD, Maslar I, Frohman LA (1985) Diethylstilbestrol inhibits tumor growth and prolactin production in rat pituitary tumors. Am J Pathol118: 379-386 18 Lloyd RV, Fields KL (1986) Regulation of dopamine receptors in the MtTIW 15 transplantable pituitary tumor by estrogen. Mol Cell Endocrinol44: 133-139
586 . R. V. Lloyd et a1. 19 Lloyd RV, Coleman K, Fields K, Nath V (1987) Analysis of prolactin and growth hormone production in hyperplastic and neoplastic rat pituitary tissues by the hemolytic plaque assay. Cancer Res 47: 1087-1092 20 Lloyd RV, Jin L, Fields K, Kulig E (1990) Regulation of prolactin gene expression in a DMBA-estrogen induced transplantable rat pituitary tumor. Am J Pathol137: 1525-1537 21 Martins T (1936) Action des hautes doses d'oe strinesur l'hypophyse in situ ou greffe'e dans la chambre anterieir de l'oeil du rat. CR Soc BioI Paris 123: 702-704 22 McEuen CS Selye H, Collip JB (1936) Some effects of prolonged administrations of oestrin in rats. Lancet i: 775-776 23 Morel Y, Albaladejo V, Bouvier J, Andrej (1982) Inhibition by 17~-estradiol of the growth of the rat pituitary transplantable tumor MtT/F4. Cancer Res 42: 1492-1497 24 Oberling C, Guerin P, Guerin M (1936) La production experimentale de tumeurs hypophysaires chez Ie rat. CR Soc BioI, Paris 123: 1152-1154
25 Scammell JG, Burrage TG, Dannies PS (1986) Hormonal induction of secretory granules in a pituitary tumor cell line. Endocrinology 119: 1543-1548 26 Shupnik MA, Gordon MS, Chin WW (1989) Tissue-specific regulation of rat estrogen receptor mRNAs. Mol Endocrinology 3: 660-665 27 Trouillas J, Morel Y, Pharaboz MO, Cordier G, Girod C, Andre J (1984) Morphofunctional modification associated with the inhibition by estradiol of MtTF 4 rat pituitary tumor growth. Cancer Res 44: 4046-4052 28 Weisz A, Bresciani F (1988) Estrogen induces expression of c-(os and c-myc proto-oncogenes in rat uterus. Mol Endocrinology 2: 816-824 29 Wiklund J, Wertz N, Gorski J (1981) A comparison of estrogen effects on uterine and pituitary growth and prolactin synthesis in F 344 and Holtzman rats. Endocrinology 109: 1700-1707 30 Zondek B (1936) Tumour of the pituitary induced with follicular hormone. Lancet i: 776-778
Received December 15, 1990 . Accepted January 16, 1991
Key words: Estrogens - Adenoma development - Pituitary tumor R. Lloyd, M.D., Department of Pathology, University of Michigan, 1500 E. Medical Center Drive, Room 2G332 - Box 0054, Ann Arbor, Michigan 48109-0054
Effects of Estrogens on Pituitary Cell and Pituitary Tumor Growth R. V. Lloyd, L. Jin, K. Fields and E. Kulig Department of Pathology, University of Michigan, Ann Arbor, Michigan, USA
SUMMARY
Estrogens have been known to induce PRL cell hyperplasia in the anterior pituitary of some species for many decades. Recent studies have shown variable susceptibility to. estrogen-induced hyperplasia in different strains of rats. The distinction between hyperplastic pituitaries and adenomas is usually not made by most investigators in this field, although true neoplasms can usually be propagated by serial transplantation. The growth of transplantable tumors is usually inhibited by estrogen in vivo. Estrogens have a biphasic effect on pituitary cell proliferation in vitro with higher concentrations of estradiol inhibit cell growth, and lower concentrations stimulating PRL secretion. Estrogens can regulate PRL gene methylation in vivo thus affecting PRL mRNA expression. Recent studies have suggested that estrogen regulates signal transduction by stimulating protein kinase C. Estrogens also regulate specific proto-oncogenes such as c-myc and c-fos. These observations may help to explain some of the regulatory effects of estrogens on cell proliferation and tumor development.
Introduction The effects of estrogens in causing anterior pituitary gland hyperplasia were reported by various investigators in 19363,5,13,21,22,24,30. Although these lesions were described as tumors, the development of transplantable pituitary tumors with chronic estrogen treatment was reported two decades later by Furth and his colleagues912
Estrogen-Induced Pituitary Hyperplasia The report of estrogen induced pituitary gland hyperplasia by six different investigators in the same year was somewhat unusual, but probably reflected the recent availability of estrogenic hormones at that time. Subsequent studies by other investigators on the cytology of estrogen-induced hyperplasia of the pituitary gland documented that the acidophilic cells were involved in this
proliferation. The careful studies of Clifton and Meyer4 showed that there was division and degranulation of 0344-0338/91/0187-0584$3.50/0
acidophils and division of chromophobic cells as well as hypersecretion of prolactin. These investigators arbitrarily defined enlarged anterior pituitaries of 30 mg or greater as tumors. This definition has been adopted by subsequent investigators. Extensive biochemical and ultrastructural studies were done on these pituitaries6 • Wiklund and co-workers showed that some strains of rats such as Fisher were more susceptible to pituitary hyperplasia than Holtzman rats 29 • These investigators documented the stimulation of PRL protein in these hyperplastic lesions. The report of Lloyd 16 showed that these enlarged pituitaries up to 150 mg were hyperplastic lesions with mixtures of various cell types and not true neoplasms. Some of the effects of estrogens on pituitary hyperplasia may be explained by changes in the arterial vasculature in the hypothalamic-pituitary region 8• Furth and his colleagues established various lines of estrogen-induced transplantable tumors after chronic treatment with estrogens9- 12 • To analyze the transition between pituitary hyperplasia
and development of transplantable tumors, Lloyd et al. 20 used dimethylbenz(a)anthracene (DMBA) and estrogen to © 1991 by Gustav Fischer Verlag, Stuttgart
Estrogens and Tumor Growth· 585
establish a transplantable pituitary cell line in Fischer 344 rats in about six months. The tumors grew readily after subcutaneous implantation and progressed from highly differentiated cells with abundant PRL hormone and mRNA production to poorly differentiated cells with serial transplant generations 2o .
ment probably involves a vast regulatory network at the level of signal transduction and proto-oncogene activation.
References
Effects of Estrogens on Transplantable and other Pituitary Tumors Although Furth et al. observed that estrogens inhibited growth of transplantable pituitary tumors, the first detailed documentation of this effect was reported by Morel et a/.2,23,27 in F 344 rats with MtTIF 4 tumors. Lloyd et at. reported similar findings in W/Fu rats with MtTIW 15 tumors 17,19. In both of these models the pituitary gland underwent PRL cell hyperplasia while growth of the transplantable tumor was inhibited. In the MtTIW 15 tumor there was inhibition of PRL production by the tumor with inhibition of tumor growth while PRL production was increased in the MtT/F 4 animals. The work of Amara and Dannies showed that estrogens had a biphasic effect on growth and on hormone expression of GH cells in vitro. Concentrations of 2 X 10- 11 M estradiol stimulated GH4C1 pituitary cells while concentrations of 3 X 10- 11 to 10- 9 M inhibited cell proliferation but stimulated PRL synthesis 1. Subsequent work by these same investigators showed that estrogens could induce differentiation in GH4C1 cells in vitro with increased numbers of secretory granules 25 . Similar findings in vivo were reported by Lloyd et al. in the DMBA-E2 induced tumor cellline2o .
Other Effects of Estrogens on Anterior Pituitary Cells Estrogens have other significant effects on pituitary cells. Dopamine D2 receptor proteins are down-regulated by estrogens 18 while the estrogen receptor protein mRNA is up-regulated by estrogen treatment26 . Recent studies in our laboratory have shown that estrogens regulate PRL DNA methylation in normal pituitary and in transplantable pituitary tumors 15 . These studies showed that in normal pituitary, MtT/F 4 and the DMBA tumors which had increased PRL mRNA expression after estrogen treatment, the PRL gene was hypomethylated. However, in the MtTlW 15 tumor which had decreased PRL expression after estrogen treatment the PRL gene was hypermethylated which correlated with the gene activity. These findings indicate that estrogens influence methylation of the PRL gene in various pituitary tissues. Estrogens have been shown to have a regulatory effect on various proto-oncogene expressions in tissues such as the hypothalamus and uterus 14,28. Estrogen regulation of c-fos and c-myc genes has been reported. In addition, protein kinase-C expression appears to be regulated by estrogens in rat pituitary tissues 7. These findings indicate that the mechanism of action of estrogens leading to pituitary cell hyperplasia and subsequent tumor develop-
1 Amara JF, Dannies PS (1983) 17~-estradiol has a biphasic effect on GH cell growth. Endocrinology 112: 1141-1143 2 AndreJ, Marchisio AM, Morel Y, Collu R (1982) Dopamine receptors in the rat pituitary and the transplantable pituitary tumor MtT/F 4: effect of chronic treatment with oestradiol. Biochem Biophys Res Commun 106: 229-235 3 Burrows H (1936) Pituitary hyperplasia in a male mouse after the administration of oestrin. Am J Cancer 28: 741-745 4 Clifton KH, Meyer RK (1956) Mechanism of anterior pituitary tumor induction by estrogen. Anat Rec 125: 65-81 5 Cramer W, Horning ES (1936) Experimental production by oestrin of pituitary tumors with hypopituitarism. Lancet i: 247-249 6 De Nicola AF Von Lawzewitsch I, Kaplan SE, Libertun C (1978) Biochemical and ultrastructural studies on estrogeninduced pituitary tumors in F 344 rats. J Natl Cancer Inst 61: 753-763 7 Drouva SV, Gorenne I, Laplante E, Rerat E, Enjalbert A, Kordon C (1990) Estradiol modulates protein kinase-C activity in the rat pituitary in vivo and in vitro. Endocrinology 126: 536-544 8 Elias KA, Weiner RI (1984) Direct arterial vascularization of estrogen-induced prolactin-secreting anterior pituitary tumors. Proc Natl Acad Sci USA 81: 4549-4553 9 Furth J and Clifton KH (1986) Experimental pituitary tumors. In: Harris G, Donovan B (Eds.) The Pituitary Glands, Vol 2: 460-497, Butterworths, London 10 Furth J, Clifton KH, Gadsen EL, Buffet RF (1956) Dependent and autonomous mammotropic pituitary tumors in rats; their somatotropic features. Cancer Res 16: 608-616 11 Furth J, Ueda G, Clifton KH (1973) The pathophysiology of pituitaries and their tumors: Methodological advances. In: Bush H (Ed) Methods in Cancer Research, Academic Press, Vol X: 201-277, New York 12 Furth J, Nakane PK, Pasteels JL (1976) Tumours of the pituitary gland. In: Turusov VS (Ed) Pathology of Tumours in Laboratory Animals, Vol I: 201-237. Tumours of the Rat, Part 2 (IARC Scientific Publications No 6), International Agency for Research on Cancer, Lyon 13 Gardner WV, Smith GM, Strong LC (1936) An observation of primary tumors of the pituitary ovaries and mammary glands in the mouse. Am J Cancer 26: 541-547 14 Insel TR (1990) Regional induction of c-(os like protein in rat brain after estradiol administration. Endocrinology 126: 1849-1853 15 Kulig FS, Landefeld TD, Lloyd RV (1990) Estrogen regulates prolactin gene methylation in transplantable rat pituitary tumor. The Endocrine Society 72nd Annual Meeting Atlanta, Georgia June 20-23. Abstract 1320, p. 354 16 Lloyd RV (1983) Estrogen-induced hyperplasia and neoplasia in the rat anterior pituitary gland. An immunohistochemical study. Am J Pathol 113: 198-206 17 Lloyd RV, Landefeld TD, Maslar I, Frohman LA (1985) Diethylstilbestrol inhibits tumor growth and prolactin production in rat pituitary tumors. Am J Pathol118: 379-386 18 Lloyd RV, Fields KL (1986) Regulation of dopamine receptors in the MtTIW 15 transplantable pituitary tumor by estrogen. Mol Cell Endocrinol44: 133-139
586 . R. V. Lloyd et a1. 19 Lloyd RV, Coleman K, Fields K, Nath V (1987) Analysis of prolactin and growth hormone production in hyperplastic and neoplastic rat pituitary tissues by the hemolytic plaque assay. Cancer Res 47: 1087-1092 20 Lloyd RV, Jin L, Fields K, Kulig E (1990) Regulation of prolactin gene expression in a DMBA-estrogen induced transplantable rat pituitary tumor. Am J Pathol137: 1525-1537 21 Martins T (1936) Action des hautes doses d'oe strinesur l'hypophyse in situ ou greffe'e dans la chambre anterieir de l'oeil du rat. CR Soc BioI Paris 123: 702-704 22 McEuen CS Selye H, Collip JB (1936) Some effects of prolonged administrations of oestrin in rats. Lancet i: 775-776 23 Morel Y, Albaladejo V, Bouvier J, Andrej (1982) Inhibition by 17~-estradiol of the growth of the rat pituitary transplantable tumor MtT/F4. Cancer Res 42: 1492-1497 24 Oberling C, Guerin P, Guerin M (1936) La production experimentale de tumeurs hypophysaires chez Ie rat. CR Soc BioI, Paris 123: 1152-1154
25 Scammell JG, Burrage TG, Dannies PS (1986) Hormonal induction of secretory granules in a pituitary tumor cell line. Endocrinology 119: 1543-1548 26 Shupnik MA, Gordon MS, Chin WW (1989) Tissue-specific regulation of rat estrogen receptor mRNAs. Mol Endocrinology 3: 660-665 27 Trouillas J, Morel Y, Pharaboz MO, Cordier G, Girod C, Andre J (1984) Morphofunctional modification associated with the inhibition by estradiol of MtTF 4 rat pituitary tumor growth. Cancer Res 44: 4046-4052 28 Weisz A, Bresciani F (1988) Estrogen induces expression of c-(os and c-myc proto-oncogenes in rat uterus. Mol Endocrinology 2: 816-824 29 Wiklund J, Wertz N, Gorski J (1981) A comparison of estrogen effects on uterine and pituitary growth and prolactin synthesis in F 344 and Holtzman rats. Endocrinology 109: 1700-1707 30 Zondek B (1936) Tumour of the pituitary induced with follicular hormone. Lancet i: 776-778
Received December 15, 1990 . Accepted January 16, 1991
Key words: Estrogens - Adenoma development - Pituitary tumor R. Lloyd, M.D., Department of Pathology, University of Michigan, 1500 E. Medical Center Drive, Room 2G332 - Box 0054, Ann Arbor, Michigan 48109-0054
