Prolactin receptors in human breast cancer cells in long-term tissue culture.

Prolactin receptors have been identified for the first time in a number of human breast cancer cell lines and a normal human breast cell line maintained in long-term tissue culture. Optimal conditions for determining the binding of 125I-labeled human prolactin to these cells were established. Five different tumor cell lines have different content of prolactin receptors ranging from 2,300 to 26,000 sites/cell. All tumor cell lines contained more prolactin receptors than does one normal breast cell line (1700 sites/cell). The prolactin receptors in these human mammary tumor cells not only bind human prolactin but also recognize other lactogenic hormones such as human growth hormone, human placental lactogen, and sheep prolactin, but not animal growth hormone, which are not lactogenic. The affinity (Ka) of binding of human prolactin to these cells is 4 x 10(9) M-1 (Kd = 2.5 x 10(-10)M). The hormone specificity and affinity for hormone of these human mammary tumor cells are very similar to that found for the rabbit mammary gland. These human mammary tumor cell lines in long-term culture should prove very useful to study the biology of prolactin receptors in living human cells and the role of prolactin in the tumorigenesis of the human breast.     

Effects of prolactin or growth hormone on growth of carcinogen-induced mammary tumors of adreno-ovariectomized rats

The effects of exogenous administration of bovine prolactin and bovine growth hormone (GH) on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor were investigated in female Sprague-Dawley rats. Rats were bilaterally adrenoovariectomized 15 days after the appearance of the first palpable mammary tumors and were treated with either prolactin or GH beginning the next morning. Marked stimulation of incidence and growth of mammary tumor and of normal mammary gland growth followed subcutaneous injections of 1.25 or 2.5 mg prolactin twice daily for 20 days. GH had no effects on mammary tumor, whereas it accelerated the growth of normal mammary gland and increased the body weight. The administration of 2.5 mg prolactin twice daily for 10 days, beginning 20 days after adreno-ovariectomy, raised the number and size of regressed mammary tumors to the pre-operative levels, while the half dose of prolactin had no effects. These results indicate that prolactin is the principal hormone responsible for the growth of DMBA-induced mammary tumor of the rat, whereas GH has only a minimal role in the growth of the tumor.     

Effects of the thiazolidinedione derivative CGP 19984 on growth and endocrine function of the MtT-W10 transplantable mammosomatotropic pituitary tumor in female rats

The thiazolidinedione derivative CGP 19984 has previously been shown to suppress the growth of hormone-dependent mammary and prostatic tumors, primarily by reducing gonadotropin and subsequently gonadal steroid secretion. The present study examines the effects of CGP 19984 on the growth and hormone secretion of the autonomous, but estrogen-responsive, MtT-W10 mammosomatotropic transplantable rat pituitary tumor. Intact tumor-bearing Wistar/Furth female rats were administered vehicle or 25, 100, or 250 mg/kg CGP 19984 p.o., 5 x week for 4 weeks. CGP 19984 was found to significantly reduce MtT-W10 tumor growth and weight and reduce prolactin and growth hormone (GH) secretion in a dose-responsive manner. A similar study in ovariectomized rats also showed that CGP 19984 treatment suppressed MtT-W10 pituitary tumor growth, weight and hormone secretion in a dose-responsive manner, suggesting a direct inhibitory action of this drug on the tumor. In a third study, bromocryptine (CB-154; 5 mg/kg) and CGP 19984 (50 mg/kg) were both found to be effective in suppressing growth of the MtT-W10 tumor in intact female rats. However, rats treated with CGP 19984 alone had reduced serum and tumor GH and prolactin concentrations, while rats treated with CB-154 alone had reduced serum and tumor prolactin, but no change in GH concentrations. These results suggest that CGP 19984 effectively inhibits growth and hormone secretion of the autonomous MtT-W10 pituitary tumor by apparently suppressing both somatotropic and lactotropic cell populations within the tumor. Furthermore, these findings indicate that CGP 19984 may be an effective alternative to CB-154 in the clinical treatment of prolactin-producing adenomas, as well as other types of pituitary adenomas.     

Effects of iodine deficiency and high-fat diet on N-nitrosomethylurea-induced mammary cancers in rats.

The effects of an altered content of dietary iodine and fat on the development of N-nitrosomethylurea-induced mammary tumors in rats were studied and correlated with thyroid and pituitary function studies. In three separate experiments, animals fed a semisynthetic diet containing 11.8% fat had an earlier time of tumor appearance and greater tumor burden than did controls maintained on a diet containing 4.6% fat. These diet-associated changes were markedly inhibited by ovariectomy, indicating that the tumor growth was hormone responsive. We examined the possibility that the diet with increased fat content enhanced tumor growth through alterations in prolactin metabolism but could find no consistent elevation in serum prolactin and no increase in pituitary prolactin synthesis in vitro. Our data further showed that rats on an iodine-deficient form of the high-fat diet had no greater tumor growth than did animals receiving an iodine-supplemented form of the same diet. We conclude from these results that iodine deficiency does not promote mammary tumorigenesis. An incidental finding of great interest was that ovariectomy led to a highly significant depression of thyroid-stimulating hormone production in vitro. This suggests that estrogens may directly influence thyroid-stimulating hormone synthesis in vivo and thus contribute to the sex-related differences in thyroid physiology.     

Stimulation of growth of carcinogen-induced mammary cancers in rats by thyrotropin-releasing hormone.

Twice-daily injections of three different doses of synthetic thyrotropin-releasing hormone (TRH), a hormone normally produced by the hypothalamus, produced significant increases in size and number of 7,12-dimethylbenz(a)anthracene-induced mammary cancers over 0.87% NaCl solution-injected control rats. When thyroidectomized rats, bearing 7,12-dimethylbenz(a)anthracene-induced mammary tumors were given the same twice-daily injections of TRH, mammary tumor growth was increased to the same extent as in intact rats given TRH, showing that the effects of TRH were not exerted via stimulation of thyroid function. The TRH-induced increments in mammary tumor growth were accompanied by significant increases in serum prolactin levels over 0.87% NaCl solution-injected controls. A single daily injection of 2-bromo-alpha-ergocryptine (CB-154), a prolactin-release inhibitor completely blocked TRH-induced mammary tumor growth and reduced serum prolactin values. These results indicate that a twice-daily pulse of TRH can stimulate mammary tumor growth by releasing prolactin from the anterior pituitary.     

Dietary protein, enhancement of N-nitrosomethylurea-induced mammary carcinogenesis, and their effect on hormone regulation in rats

The effect of supplemental dietary protein (casein) fed with high fat diets was investigated using the N-nitrosomethylurea-induced mammary tumor model. Isocaloric diets containing casein and corn oil at 19 and 15% (normal protein-high fat) or 33 and 15% (high protein-high fat) were fed ad libitum to Sprague-Dawley mother rats. Female offspring continued on the diet. Food consumption and growth curves were similar over the entire growth period. N-Nitrosomethylurea (50 mg/kg body weight) or saline was administered at 7 and 8 weeks of age via the tail vein. Dietary protein had no effect on serum prolactin or growth hormone throughout the estrous cycle: Prior to carcinogen administration, at 7 weeks old, proestrus at 5 p.m., serum prolactin was 231.6 +/- 141.0 (SE) ng/ml (12 rats) versus 292.2 +/- 141.0 (13 rats) for normal versus high protein diet groups, respectively. No difference was noted after carcinogen injection at 9, 13, 28, and 33 weeks of age. Similarly no effect was noted on serum growth hormone activity. Tumor latency was 7 weeks and incidence was 100% in normal protein (24 rats) and high protein (39 rats) groups 28 weeks after carcinogen treatment. The number of tumors per rat (4.38 +/- 0.37 versus 2.87 +/- 0.35, P less than 0.002) and average tumor weight (17.97 +/- 2.63 versus 9.94 +/- 2.92 g) were significantly greater in the high protein group. Study indicates that diet or carcinogen treatment did not alter hormone regulation during the estrous cycle. However, supplemental dietary protein increased the effect of high fat diets enhancing the mammary tumor burden.     

Pituitary adenomas. Immunocytochemical study of 150 tumors with clinicopathologic correlation

Retrospective immunocytochemical study of prolactin, growth hormone, ACTH, TSH and gonadotropins was performed on 150 pituitary adenomas from 142 patients and the results were correlated with clinical manifestations. There were 60 prolactin-positive tumors, 13 growth hormone-positive tumors, nine ACTH-positive tumors and seven gonadotropin-positive tumors. Seven tumors showed positivity for both prolactin and growth hormone, one tumor was positive for prolactin and ACTH and another was positive for prolactin and TSH. Fifty-two tumors were negative for all the hormones. In the hormone secreting tumors, the results of immunocytochemical study correlated very well with clinical manifestations, while most of the hormone-negative tumors were nonfunctioning clinically. This study demonstrates the reliability of the immunocytochemical method in clinicopathologic study of pituitary adenomas.     

Protein and RNA synthesis in pituitary tumors from F344 rats given implants of estrogen.

The synthesis of total proteins, growth hormone, and prolactin and the incorporation of radioactive precursors into RNA was studied in Pituitaries from normal F344 rats and rats given implants of 15 mg diethylstilbestrol (DES).Prolonged DES treatment (greater than 50 days) induced pituitary tumors in male and female rats. The tumor tissue had a high rate of cell protein synthesis and an unusual capacity to synthesize a single-protein hormone (prolactin). After 17 days of DES treatment, the increase in prolactin synthesis in the hyperplastic pituitaries was not as marked as that in the tumors. At the time of tumor induction and high prolactin synthesis, incorporation of uridine or cytidine into RNA was not stimulated, and orotic acid incorporation in tumors from male rats was decreased. During early estrogen treatment (5 and 17 days), significantly less uridine was incorporated into RNA. These data suggested that the increment in protein and hormone synthesis promoted by DES may be related to a decrease in RNA turnover.     

Serum, pituitary and urine concentrations of prolactin and growth hormone in eight strains of mice with varying incidence of mammary tumors

Eight inbred strains of mice with varying incidences of spontaneous mammary tumor were compared in regard to prolactin and growth hormone concentrations in sera, pituitary glands and urine. Serum prolactin was compared under basal conditions as well as after stimulation with perphenazine. Both hormones were measured with specific, homologous radioimmunoassays. Although some strains having a high incidence of mammary tumors had high levels of prolactin in sera, urine and pituitary glands, neither basal nor perphenazine-induced serum concentrations showed a consistent pattern across mouse strains that correlated with the incidence of mammary tumors. Growth hormone levels in sera, pituitary glands and urine also had no characteristic pattern that applied to all strains studied. The ratio of prolactin depleted from the pituitary gland to prolactin detected in serum after perphenazine injection, which reflected the metabolic clearance rate of prolactin, was highest in two strains with a high incidence of mammary tumors and relatively lower in low-tumor strains. These results suggest that if prolactin plays a part in mammary tumor development in mice, its mechanism varies with strains: while hyperprolactinemia may be the means in some strains, a peculiarity in the metabolism of the hormone may be more important in others.     

Prolactin binding to R3230AC mammary carcinoma and liver in hormone-treated and diabetic rats.

Specific 125I-labeled prolactin binding was measured in membrane particles prepared from R3230AC mammary carcinoma and liver of tumor-bearing Fischer rats after either prolactin, estrogen, or lergotrile mesylate treatment, or after the induction of diabetes by streptozotocin. Hormone binding to tumors was decreased by treatment with prolactin (0.5 or 1 mg/day) or estradiol valerate (7.5 mg/kg/week). In contrast, prolactin treatment did not affect prolactin binding to liver membrane particles, but estradiol valerate treatment resulted in a four-fold increase in prolactin binding to this tissue. Lergotrile mesylate, which lowers plasma prolactin levels, did not affect tumor growth or prolactin binding to either tumor or liver. Prolactin binding to both tumor and liver was significantly reduced in diabetic rats, suggesting that insulin may play an important role in controlling tissue sensitivity to prolactin. Specific binding of 125I-labeled prolactin to enzymatically dissociated cells from R3230AC tumors was demonstrated in vitro. The binding capacity of the cells was found to be of the same order of magnitude as the binding capacity in membrane preparations when appropriate corrections were applied for yields of cells and membranes. R3230AC tumor, which is responsive to prolactin appears therefore to be a useful model system for further study aimed at elucidation of growth and metabolic response to the hormone prolactin in breast cancer.     

Regulation of mammary tumor virus production by prolactin in BALB/cfC3H mouse normal mammary epithelial cells in vitro.

Hormonal regulation of mammary tumor virus (MTV) production, has been analyzed with normal mammary epithelial cells from chronically infected BALB/cfC3H mice. The effect of prolactin in terms of increased MTV production was not reproducibly observed in cells cultured in tissue culture dishes, whereas the cells grown on floating collagen gels consistently responded to prolactin in a dose-dependent manner. Of the three media tested. Dulbecco's modified Eagle's medium was found to be the best in terms of responsiveness to prolactin and in maximal MTV production. Specificity studies with other pituitary and placental hormones in place of prolactin have shown that both growth hormones and human placental lactogen can replace prolactin, whereas follicle-stimulating hormone, luteinizing hormone, and thyrotrophin were ineffective. Contrary to the mammary tumor systems, where it has been shown that insulin and glucocorticoid can maximally stimulate MTV production, these hormones alone elicited only a small response in the absence of prolactin in normal mammary epithelial cells. Although prolactin alone had very little effect by itself, its presence was necessary (permissive effect) in order for the glucocorticoids to be able to maximally stimulate MTV production in normal cells.     

Primary cultures of human benign mastopathies and mammary carcinomas; growth factor requirements

Primary cultures of non malignant human breast tissues, benign mastopathies and breast carcinoma were performed in defined culture conditions. Epithelial cells from these primary cultures were characterized for mammary epithelial cell specific markers, for in vitro cell proliferation, for steroid receptors and hormone sensitivity (estradiol, progesterone and prolactin) and for EGF sensitivity. We show that although some mastopathies have estradiol and progesterone receptors, they did not respond to hormone treatment. Human prolactin had no effect on the proliferation of one mastopathy but stimulates the cell growth of another fibrocystic mastopathy. EGF was capable of stimulating the three types of primary cultures. As regards growth characteristics, steroid hormone receptors and prolactin sensitivity, phenotypes of mastopathy cells differ from each other; some are similar to non malignant cells, whereas others are comparable to tumor cells.     

External irradiation of growth hormone producing pituitary adenomas: prolactin as a marker of hypothalamic and pituitary effects

Fifty-six patients with acromegaly were treated with external irradiation, 50 Gy, after unsuccessful pituitary surgery. A 50% reduction of pre-irradiation growth hormone levels was obtained in 51/56 patients. This level was reached after 26 +/- 14 months in 33 patients with prolactin levels less than 25 micrograms/l at diagnosis, after 21 +/- 17 months in 18 patients with prolactin greater than or equal to 25 micrograms/l, and after 20 +/- 21 months in 12 patients with prolactin greater than 40 micrograms/l at diagnosis. A further 50% decrease of growth hormone levels was obtained in 40/51 patients 42 +/- 22 months after radiotherapy, indicating that in clearly responsive patients, the growth hormone depression after radiotherapy follows a first order reaction. Four patients did not reach a 50% reduction of growth hormone levels 48-80 months after radiotherapy. During 10 years of follow-up, the growth hormone depression tended to be more pronounced in patients with mixed secretion of growth hormone and prolactin. The reduction of growth hormone levels was not correlated with the irradiated volume or the cumulative radiation effect. Within the first year, prolactin increased within the normal range in normoprolactinemic patients and remained so during follow-up. In hyperprolactinemic patients, prolactin decreased successively but to a lesser extent than growth hormone. Pituitary insufficiencies increased over time and three patients developed GH-insufficiency. Hypothalamic damage as indicated by prolactin changes was a regular phenomenon after radiotherapy.     

Interactions between estrogens, prolactin, and growth hormone on the growth of N-nitrosomethylurea-induced rat mammary tumors

Rats bearing N-nitrosomethylurea-induced mammary tumors regressing after ovariectomy were assigned to control or treatment groups. All control tumors continued to regress, while the serum prolactin levels were subnormal. Estrogen replacement stimulated tumor regrowth, and increased the serum prolactin. Pergolide further suppressed the postovariectomy serum prolactin, and all tumors continued to regress. When estrogen and pergolide were given together, 32% of tumors progressed despite low serum prolactins. Ovine prolactin, delivered to ovariectomized rats at a rate of 40 micrograms/hr, caused 3 of 10 tumors to progress, 3 to become static, and 4 to continue regression. Prolactin also maintained the growth of 4 of 8 tumors after hypophysectomy, and arrested regression of 3 others. Posthypophysectomy regression was also prevented and growth maintained by the simultaneous administration of estrogen and growth hormone.     

Polyostotic fibrous dysplasia with gigantism and huge pelvic tumor: a rare case of McCune–Albright syndrome

We report a rare case of polyostotic fibrous dysplasia on endocrine hyperfunction with elevated human growth hormone and normal serum level of prolactin. There were some differential points of gender, gigantism, endocrine function, and GNAS gene from McCune–Albright syndrome. Malignant transformation was suspected in the pelvic tumor from imaging because rapid growth of the tumor by imaging was observed; however, no malignant change occurred in this case.     

Maternal and gestational correlates of pregnancy prolactin and growth hormone in USA and China.

The objective of this study is to determine correlates of prolactin and growth hormone levels among pregnant women in the USA and China. We studied 304 pregnant Caucasian and 335 pregnant Chinese women. Levels of prolactin and growth hormone were measured at weeks 16 and 27 of gestation, and correlated with maternal, gestational and perinatal characteristics. Both growth hormone and, to a lesser extent, prolactin were inversely associated with pregnancy weight and body mass index, history of a previous live birth and newborn size, whereas educated women had higher levels of both hormones. Growth hormone levels were lower in women who gained more weight, smoked and had nausea and vomiting during pregnancy, whereas prolactin increased with longer total gestation. We found robust associations between maternal and newborn characteristics on the one hand and prolactin and growth hormone during pregnancy on the other.     

Changes in plasma hormone profiles after tumor transplantation into syngeneic and allogeneic rats

Transplantation of 2 chemically (DMBA, MCA)-induced tumors into syngeneic female or male DA strain rats elicited hormonal changes during tumor growth. Plasma levels of 7 different hormones were studied. Tumor cells in syngeneic recipients produced a biphasic decrease in insulin, an early increase in prolactin, and a late-phase decrease in thyroxine. Corticosterone decreased in female tumor bearers but increased in males. This difference may reflect differences in the tumors transplanted. Male rats had a decrease in testosterone during the late phase of tumor growth, while females had a biphasic decrease in progesterone and a late-phase increase in growth hormone. The tumors used were moderately immunogenic in syngeneic recipients. However, tumor transplantation to allogeneic recipients produced an early decrease in growth hormone and no change in insulin, corticosterone or thyroxine. Further, transplantation of normal liver cells to syngeneic or allogeneic recipients produced no hormonal abnormalities. This study demonstrates that hormonal changes which are not observed with normal cells or allogeneic tumor transplantation can occur within 2 days of syngeneic tumor transplantation. Progressive tumor growth is characterized by a worsening endocrine imbalance which involves multiple hormone systems.     

Prolactin and growth hormone levels in premenopausal women with breast cancer and healthy women with a strong family history of breast cancer

Although both prolactin and growth hormone are believed to play roles in the development and growth of rodent mammary cancer, the role of these hormones in human breast cancer is uncertain. Under carefully specified conditions, serum levels of these hormones were determined by radioimmunoassay (RIA) and prolactin was determined by bioassay in 18 premenopausal women with breast cancer, 23 healthy women with a strong family history of breast cancer, and 39 healthy women with no significant family history of breast cancer. Parity was associated strongly with decreased prolactin levels, and increasing age was associated strongly with decreased growth hormone levels. After controlling for these variables, no differences in prolactin or growth hormone levels were found among the three groups of women. These data do not support roles for these RIA-measured hormones or bioassay-measured prolactin in premenopausal or familial breast cancer in omnivorous white women.     

The role of prolactin and growth hormone in breast cancer

This review will focus on the role for prolactin (PRL) and growth hormone (GH) in mammary tumor formation. Much attention has previously been focused on circulating levels of GH/PRL in relation to mammary tumor formation. We will review data demonstrating that these ligands also could be produced locally in different organs, including the mammary gland and mammary tumors, and suggest that this local production may be of importance for pathological conditions. We will also discuss mechanisms for crosstalk between steroids and GH/PRL. A crosstalk between GH- and PRL response is possible at multiple levels. In the human, GH can activate both the prolactin receptor (PRLR) and the growth hormone receptor (GHR). We have demonstrated that activation of the PRLR, but not the GHR, is inducing mammary tumors in transgenic mice. Furthermore, the elevated levels of insulin-like growth factor 1 (IGF-I) seen in the GHR activating transgenic mice is not sufficient for tumor induction. The induced tumors express functionally active prolactin that could be of importance for the tumor formation. Paracrine/aurocrine stimulation by PRL may be more important than PRL transported via the circulation. In women, the role for stimulation of the PRLR and/or the GHR in mammary tumor formation has not been proven, although experiments from primates suggest that the PRLR could be of importance.     

Serum prolactin levels are positively associated with mammographic density in postmenopausal women

Background Prolactin is a polypeptide hormone that promotes normal breast proliferation and differentiation, but it is also implicated in the development and growth of mammary tumors. Mammographic density is a strong, independent predictor of breast cancer and, therefore, a potential surrogate indicator of breast cancer risk. Methods To test the hypothesis that serum prolactin is positively related to mammographic density, we conducted a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) Mammographic Density Study. Based on prior work, we further hypothesized that this association would be apparent only in women who had not recently used postmenopausal hormone therapy (HT). Results In linear regression models adjusted for age, body mass index, race, smoking, alcohol use, parity and physical activity, among the 400 women who were not recent users of HT, prolactin was positively and statistically significantly associated with mammographic density (Beta log base 2 prolactin 0.0369 [95% CI: 0.0094–0.0645]. Thus, for each doubling of serum prolactin, there was an absolute increase in mammographic density of 3.69%. Additional adjustment for serum levels of estradiol, progesterone, sex hormone binding globulin and age at first pregnancy did not affect this result. There was no association between prolactin and mammographic density among the 169 participants who had recently used HT. Conclusion The correspondence between higher prolactin and higher mammographic density is consistent with prolactin’s mitogenic properties and the associations between prolactin and breast tumor promotion. These results support the thesis that prolactin deserves investigation as a target for breast cancer risk reduction.