Prolactin and mammary gland carcinogenesis. The problem of human prolactin

Effect of Sulpiride on Mammary Tumor Growth

The daily subcutaneous injection of sulpiride produced increase tumor growth and decrease of survival in DBA/2 mice bearing a transplanted mammary gland tumor. It is proposed that sulpiride effect may be mediated by the augment of prolactin level in serum.

Effect of adjuvant chemotherapy on the circulating levels of pituitary hormones in postmenopausal breast cancer patients

The effect of adjuvant chemotherapy on the circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin (PRL) has been investigated in postmenopausal breast cancer patients. In the patients who received adjuvant CMF-chemotherapy, there was a significant decrease in the circulating FSH, LH and PRL levels compared to healthy age-matched controls. A positive correlation was found between this decline in the FSH, LH and PRL values and the regression of tumor size following chemotherapy regimen.

Serum prolactin levels and their relationship to survival in women with operable breast cancer

The prognostic value of serum prolactin levels was assessed in a sequential series of 739 patients who were initially treated at Guy's Hospital, London, between 1975 and 1980. Prolactin was measured in 472 patients 1 day before (Hpr1) and in 457 patients 10 days after (Hpr2) mastectomy. Follow-up of the patients was up to August 1992 giving 6139 women-years with a median follow-up time of 11.5 years (13.7 for patients still living and 5.1 for those dead). The association between the three prolactin variables and reproductive and clinical factors was examined before assessing the prognostic value of prolactin levels in terms of overall, disease-specific and disease-free survival. Multivariate survival models were used in order to adjust for the effect of other prognostic variables. These were found to be: tumour size, degree of nodal involvement, tumour grade and age at diagnosis. The results showed that high Hpr2 or high postoperative increase in prolactin (i.e. Hpr2-Hpr1) were significantly related to shorter disease-specific survival (p = 0.04 and 0.01, respectively) in postmenopausal women. In addition there was some indication, which did not attain formal significance, for this association to occur for disease-free survival. Thus the rise in blood prolactin levels after surgery may be a weak indicator of poor prognosis of breast cancer in postmenopausal women.

Steroid hormone receptor regulation by various hormonal factors during mammary development and growth in the normal mouse

The studies described herein are focused on the nature and regulation of estrogen receptors in normal mammary tissue, with the rationale that manipulation of these receptors is the sole basis for endocrine therapy of human breast cancer. Various features of this complex system have been uncovered by our studies. The presence of different forms of cytosol estrogen receptor, fluctuating in unison with glandular stimulation, results in differential responsiveness of the cells. Tissue that is relatively estrogen-starved presents its receptors in a form that avidly attract the limited available ligands and can hastily put them to use in the nucleus. In contrast, the receptor system in the highly stimulated state displays a sort of refractoriness to estrogen, being relatively sluggish in its responsiveness. Once formed, however, these latter complexes are probably far more effective in terms of eliciting estrogenic responses, since they have an enhanced affinity for DNA and a prolonged half-life. (Table; see text) Prolactin is clearly a very important mediator of the action of estrogen on the mammary gland estrogen receptors, presenting a tissue-specific difference in comparison with the regulation of the uterine estrogen-receptor system. An odd finding was that prolactin inhibits nuclear retention of the estrogen receptor (and probably the progesterone receptor), an effect that is counterproductive to its very strong positive action on the level of intracellular receptor. Perhaps prolactin is the gross effector of receptor fluctuation, allowing estrogen the privilege of dictating the degree of receptor function; indeed our data on the dose-responsiveness of estrogen action and the effects of bromocriptine indicate that a portion of the estrogenic stimulation is not mediated by prolactin. An interesting sidelight of these studies was the finding that high levels of bromocriptine, pharmacologic in terms of prolactin suppression, exhibited an inhibitory effect on nuclear retention of estrogen receptors that was independent of, and did not prevent subsequent elicitation of, the action of prolactin on the receptors. The role of prolactin in tumorigenesis is well established in experimental animals, but its role in the human disease is not clear. Although prolactin receptors have been measured in human breast cancer, there does not appear to be any distinguishable correlation with the presence of estrogen or progesterone receptors. While it is a bit premature to draw conclusions, initial trials of bromocriptine usage have not been supportive of beneficial effects of such treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Diurnal variations in prolactin and growth hormone levels in normal premenopausal vegetarian and omnivorous women

Diurnal levels of plasma prolactin and growth hormone were measured in 47 normal premenopausal women, 26 of whom were established vegetarians and 21 of whom were omnivorous controls. There were no differences between the median prolactin levels of the two groups during a 24-hour period of investigation. When the groups were further subdivided into ovolactovegetarians and vegans, still no differences were found in prolactin secretion. In contrast, the vegetarian women exhibited elevation of growth hormone levels during the period of study, which was particularly marked at midnight and 10 A.M.

Neoplastic and nonneoplastic lesions in aging female rats with special reference to the functional morphology of the hyperplastic and neoplastic changes in the pituitary gland

Hyperplastic and neoplastic lesions in the mammary glands, uterus, adrenals and pituitary glands of untreated aging female rats were evaluated. The most common lesions in the uterus, mammary glands and adrenal cortex were endometrial stromal polyps, fibroadenomas and nodular hyperplasias, respectively. A few malignant neoplasias were found in the uterus and mammary glands. The pituitary glands of the senile untreated rats had diffuse hyperplasia and/or hypertrophy of PRL, STH and ACTH cells. In 25 out of 52 rats (48%), pituitary adenomas were detected. Histological examination showed that the adenomas were made up of immature cells, a combination of ACTH and immature cells, prolactin cells, or intermediate zone cells. The cytological changes in the hypophyseal cell types in the senile rats were usually accompanied by spontaneous neoplasias of the mammary glands. The possible role of hypophyseal hormones in the neoplasias of the mammary glands and the adrenal cortex is discussed. The present study has also shown that the variation in the reproductive state of the aging female rats, as assessed from ovarian morphology, had no striking effect on the incidence or the severity of the hyperplastic/neoplastic lesions in the organs examined.

Radioiodinated prolactin as a potential mammary tumor localizing agent

The feasibility of using radioiodinated prolactin for early detection of solid mammary tumors was studied in the rat. Radioiodinated prolactin was first injected into tumored and control rats in order to define the localization of the labeled hormone in their target organs, then it was injected into extracorporeal blood-loop of tumored and healthy rats, in order to study its clearance in those animals. At 15 min post injection, 75-82% of the labeled hormone was recovered, of which 4-5% were counted in the tumor. Deiodination was apparent only 30 min after injection. As much as high deposition of the labeled hormone was not achieved in the hormone-dependent tumor lines investigated, some of the pitfalls that may be encountered are documented. The clearance of the labeled prolactin as determined by the blood-loop technique is 3.3 min in the R3230 tumor, and 6.4 min in the 13762 mammary tumor. The healthy rats had a blood clearance of 4.6 min.

Cytological study on the anterior pituitary of senile untreated beagle bitches with spontaneous mammary tumours

Pituitaries were obtained from senile untreated Beagle bitches of comparable age (7-9 years) and genital status. The animals were divided into three groups; one was normal (without mammary lesions), one had benign tumours and one had mammary adenocarcinomas. PRL-, STH-, ACTH- and gonadotrophin-producing cells are studied and counted in serial paraffin sections stained with histochemical techniques. The animals with mammary malignancy displayed a marked increase in the relative number of PRL and ACTH cells with morphological signs of higher secretory activity in most cells, compared with that in normal bitches or bitches with benign tumours. STH cells in bitches with adenocarcinomas were reduced in number; however the secretory activity in these animals was the same as that observed in the normal bitches. In the animals with benign mammary tumours, STH cells showed morphological indication of higher secretory activity than in the other groups. PRL and ACTH cells were slightly increased in number and had slightly higher activity than that in normal bitches. These findings may suggest a role for hypophyseal hormones in mammary neoplasias.

A prospective study of plasma prolactin levels and subsequent risk of breast cancer

Plasma prolactin was measured in 2,572 pre-menopausal, 628 menopausal, and 1,666 peri- and post-menopausal women who were apparently healthy. Breast cancer was subsequently diagnosed in 47 of these women at a median time of 5 years after blood collection (pre-cancer cases). Prolactin levels in pre-menopausal cases increased significantly with age whereas this was not found in matched controls. The perimenopausal cases were characterized by extreme variability in prolactin levels. In post-menopausal women who developed breast cancer, the prolactin levels were significantly elevated, being at or above the 70th percentile for the controls. In this group the results are consistent with prolactin acting as a late-stage tumour promoter.

Pituitary gonadotrophins and prolactin in patients with endometrial cancer, fibroids or ovarian tumours

The serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH) and, prolactin (PRL) were measured before and after gonadotrophin releasing hormone (GnRH) and thyrotrophin releasing hormone (TRH) stimulation in 17 patients with endometrial cancer, in 15 patients with uterine fibroids, in 11 patients with ovarian cystadenomas or cancer and in 14 age-matched controls. The women with fibroids had a low FSH level and a diminished FSH response to GnRH but an excessive PRL response to TRH while the other patient groups did not differ from the controls. The results indicate no relation between pituitary function and endometrial or ovarian tumor.

Inhibition of mammary tumorigenesis in GR mice with 2-bromo-alpha-ergocryptine

A high incidence of mammary tumors is found in multiparous GR mice during the 2nd and 3rd pregnancies and in nulliparous GR mice treated with estrone/progesterone. The purpose of this study was to determine if prolactin is a contributing hormone in the genesis of these neoplasms. In one series of experiments, 238 15-week-old nulliparous GR mice were treated with estrone (drinking water, 0.5 mg/liter) plus progesterone (30 mg progesterone pellet with cholesterol, implanted SC once monthly) for a period of 13 weeks. Half of these mice were injected SC once daily with 100 micrograms of the prolactin-suppressing drug 2-bromo-alpha-ergocryptine (CB-154) for the duration of hormone treatment, and the other half were injected SC once daily with 0.9% NaCl solution (controls). In another series of experiments, 87 pregnant GR mice were divided into two groups and injected SC once daily from day 7 to 21 of pregnancy with 0.9% NaCl solution (controls) or CB-154 (100 micrograms/mouse). In the first series, the numbers of mice with mammary tumors and total number of mammary tumors were: controls, 58/119 (49%) and 73; CB-154 treatment, 34/119 (29%) and 37, respectively. In the second series, the numbers were: controls, 39/44 (89%) and 73; CB-154 treatment, 24/43 (56%) and 43, respectively. In both studies, CB-154 treatment significantly (p less than 0.05-0.005) reduced the percentage of mice with mammary tumors and total number of mammary tumors. These results provide evidence that prolactin is a contributing hormone in the genesis of estrone/progesterone and pregnancy-induced mammary tumors in female GR mice.

[Mammotropic and somatotropic pituitary cells in spontaneous mammary tumor bearing C3H female mice. A quantitative electron microscope study]

Pituitaries of mammary tumor-bearing mice (C3H) were examined by quantitative electron microscopy. The results indicate that considerable modifications occur in mammotropic and somatotropic cells. Both types show an increase of the surface of the endoplasmic reticulum and a decrease of the volume of secretory granules (in percent of cytoplasmic volume), suggesting a heightened secretory activity of these cells during mammary carcinogenesis.

Effect of prolactin and bromocriptine on growth of transplanted hormone-dependent mouse mammary tumours

Administration of ovine prolactin alone supported growth of hormone-dependent GR mouse mammary tumours. Growth of hormone-independent tumours was not stimulated. Furthermore, administration of bromocriptine, a compound that inhibits release of prolactin from the pituitary gland, was shown to inhibit the growth of hormone-dependent tumours in animals receiving treatment with progesterone + oestrone. Administration of prolactin or bromocriptine to mice bearing tumours that grew independently of progesterone + oestrone treatment had no influence on tumour growth. We conclude that direct as well as indirect evidence has been found for the involvement of prolactin in the growth of transplanted, hormone-dependent GR mouse mammary tumours.

Plasma prolactin and its relationship to risk factors in human breast cancer

The prolactin concentration has been determined in plasma from ostensibly healthy women living on the Island of Guernsey. There were 102, 42, and 41 women who had a mother, sister or maternal aunt, respectively, with breast cancer. The remaining 184 women in this study claimed to have no known family history of breast cancer and were used as a control group. The increased risk of breast cancer due to family history was not associated with a raised mean prolactin level compared to the control group. However, in the luteal phase of the menstrual cycle, daughters of breast cancer patients had significantly raised levels of prolactin at 19.00 h. There were no abnormalities in the mean plasma prolactin levels for the above groups associated with differences in age at first child, age at menarche, interval between age at menarche and first child, and body weight of post-menopausal women. (All these factors have been reported to influence breast cancer risk). It is concluded that prolactin has no obvious function in the aetiology of breast cancer. If it is involved, the mechanism by which it acts must be subtle and concerned with the homeostatic control governing nycthemeral prolactin rhythms.

Plasma prolactin responses to thyrotropin-releasing hormone in patients with breast cancer

Plasma human prolactin levels were measured by homologous radioimmunoassay in patients with primary breast cancer and in normal women of similar age. In normal controls mean (+/- SEM) basal plasma prolactin levels were 11.9 +/- 1.5 ng/ml and intravenous injection of synthetic thyrotropin-releasing hormone (TRH), 500 mug, caused a significant rise in plasma prolactin in all subjects examined with a maximum response of 52.6 +/- 3.3 ng/ml (mean +/- SEM). Markedly high plasma prolactin levels and exaggerated plasma prolactin responses to TRH were demonstrated in some patients with breast cancer. However, mean basal plasma prolactin levels and mean plasma prolactin increments following TRH in patients with breast cancer did not differ significantly from those in normal subjects. Plasma prolactin responses to TRH were slightly blunted during the administration of androgen in patients with breast cancer. These results suggest that some of the patients with primary breast cancer have abnormal prolactin secretion.

Controlled clinical trial of L-dopa and nafoxidine in advanced breast cancer: an E.O.R.T.C. study

L-Dopa lowers plasma prolactin levels, and there have been reports that patients with advanced breast cancer have been successfully treated with L-dopa. To test the potential value of L-dopa in this disease a randomized clinical trial of L-dopa and nafoxidine (as the reference compound) was conducted in postmenopausal women with advanced breast cancer. Objective remissions were obtained in sever out of 36 patients (19%) treated with nafoxidine but in none out of 40 patients treated with L-dopa. L-Dopa in the dose schedule used seems to be ineffective in advanced breast cancer.

Changing patterns in endometrial adenocarcinoma: a study of 291 consecutive cases at a large private hospital, 1960-1973

The experience with endometrial adenocarcinoma in postmennpausal women in a private hospital is reviewed for the time period from 1960 to 1973. By dividing the investigation into time periods from 1960 to 1966 and from 1967 to 1973 a real increase in the incidence of this lesion in the latter is demonstrated. The data suggest that the increase may be due in part to the increased use of exogenous estrogen in postmenopausal women. A treatment regimen to circumvent this increase is offered.

Plasma prolactin activity in inappropriate lactation

Using a bioassay dependent on the development of a lactogenic response in rabbit mammary tissue cultured in vitro, prolactin distinct from immunoreactive growth hormone has been found in the plasma of patients of both sexes with inappropriate lactation with and without evidence of pituitary tumours. It has also been found in one patient with primary hypothyroidism and galactorrhoea, and in another during chlorpromazine therapy, but not in nine patients with gynaecomastia without galactorrhoea. Plasma prolactin levels were examined in seven patients during oral glucose tolerance tests: no change occurred in the four patients with pituitary tumours, but the levels were suppressed in the three patients with normal pituitary fossae. Prolactin appears to be a distinct pituitary hormone in man, as in animals, and also to be aetiologically related to states of inappropriate lactation.