Use of tissue-specific promoters in the regulation of aromatase cytochrome P450 gene expression in human testicular and ovarian sex cord tumors, as well as in normal fetal and adult gonads.

We have previously demonstrated that the tissue-specific regulation of human aromatase cytochrome P450 (P450arom) gene expression is, in part, the consequence of the use of tissue-specific promoters. Promoter I.1 (PI.1) and PI.2-specific transcripts are expressed in the placenta, whereas promoter II (PII) appears to be the only active promoter in the corpus luteum. Testicular and ovarian sex cord tumors with annular tubules (SCTATs) associated with gynecomastia in prepubertal boys and isosexual precocity in girls with Peutz-Jeghers syndrome (P-JS) have been previously reported. In the present study, we investigated the regulatory elements directing P450arom gene transcription in samples of SCTAT from three prepubertal boys and a girl with P-JS and an ovarian granulosa cell tumor from an adult woman, as well as in healthy fetal and adult testicular and ovarian tissues. Placental tissue was used as a control. Using polymerase chain reaction linked to reverse transcription and northern blotting, we determined the tissue-specific use of various P450arom promoters by analyzing specific 5'-termini from messenger RNA templates. Results indicate a universal gonadal promoter (PII) directs P450arom gene expression in healthy fetal and adult ovaries and testes, as well as in SCTAT of the P-JS and an adult ovarian granulosa cell tumor. These results are interpreted to mean that use of PII in human ovary and testis is preserved from the fetal period into adult life as well as in transformed neoplastic Sertoli and granulosa cells. On the other hand, transcripts from placenta are specific for PI.1 (and to a much lesser extent, PI.2). In SCTAT, immunoreactive P450arom is detected only in the cytoplasm of neoplastic cells, whereas the normal-appearing sex cords do not contain any immunoreactive P450arom. These results further suggest that the markedly increased aromatase expression of these transformed neoplastic cells is not a consequence of using different tissue-specific promoters. Rather it appears to involve activation (or failure of inhibition) of the upstream regulatory elements of the same promoter, which is normally functional in all gonadal tissues, namely the proximal PII.

Use of tissue-specific promoters in the regulation of aromatase cytochrome P450 gene expression in human testicular and ovarian sex cord tumors, as well as in normal fetal and adult gonads.

We have previously demonstrated that the tissue-specific regulation of human aromatase cytochrome P450 (P450arom) gene expression is, in part, the consequence of the use of tissue-specific promoters. Promoter I.1 (PI.1) and PI.2-specific transcripts are expressed in the placenta, whereas promoter II (PII) appears to be the only active promoter in the corpus luteum. Testicular and ovarian sex cord tumors with annular tubules (SCTATs) associated with gynecomastia in prepubertal boys and isosexual precocity in girls with Peutz-Jeghers syndrome (P-JS) have been previously reported. In the present study, we investigated the regulatory elements directing P450arom gene transcription in samples of SCTAT from three prepubertal boys and a girl with P-JS and an ovarian granulosa cell tumor from an adult woman, as well as in healthy fetal and adult testicular and ovarian tissues. Placental tissue was used as a control. Using polymerase chain reaction linked to reverse transcription and northern blotting, we determined the tissue-specific use of various P450arom promoters by analyzing specific 5'-termini from messenger RNA templates. Results indicate a universal gonadal promoter (PII) directs P450arom gene expression in healthy fetal and adult ovaries and testes, as well as in SCTAT of the P-JS and an adult ovarian granulosa cell tumor. These results are interpreted to mean that use of PII in human ovary and testis is preserved from the fetal period into adult life as well as in transformed neoplastic Sertoli and granulosa cells. On the other hand, transcripts from placenta are specific for PI.1 (and to a much lesser extent, PI.2). In SCTAT, immunoreactive P450arom is detected only in the cytoplasm of neoplastic cells, whereas the normal-appearing sex cords do not contain any immunoreactive P450arom. These results further suggest that the markedly increased aromatase expression of these transformed neoplastic cells is not a consequence of using different tissue-specific promoters. Rather it appears to involve activation (or failure of inhibition) of the upstream regulatory elements of the same promoter, which is normally functional in all gonadal tissues, namely the proximal PII.

Detection of aromatase and keratinocyte growth factor expression in breast tumors using reverse transcription-polymerase chain reaction.

It has been proposed that local production of estrogen may contribute to breast tumor growth, in part by regulating growth factor production. In view of this, we studied the expression of mRNAs for aromatase cytochrome P-450, the enzyme which catalyzes estrogen synthesis, and keratinocyte growth factor (KGF), a heparin-binding growth factor specific for epithelial cells, in breast tumors. In order to detect mRNAs of low-abundance, reverse transcription-polymerase chain reaction (RT-PCR) was used. RNA from breast tumors and normal breast tissue was reverse transcribed and then amplified using oligonucleotide primers for human aromatase or KGF. Twelve of 15 breast tumor samples yielded variable amounts of aromatase PCR product, but consistently strong KGF PCR signals. Of the three aromatase mRNA-negative samples, two gave weak KGF signals while one was negative for KGF. Both aromatase and KGF transcripts were also detected in all five normal breast tissue samples examined. These results indicate that a high proportion of breast tumors have the potential to produce aromatase and KGF, both of which could play important roles in their growth. The results also suggest that RT-PCR can be used to evaluate local expression of growth mediators in tumors.

Expression of aromatase cytochrome P-450 in premenopausal and postmenopausal human ovaries: an immunocytochemical study.

The cellular distribution of the aromatase cytochrome P-450 enzyme in human ovaries has been investigated immunocytochemically, using an aromatase-specific monoclonal antibody. Ovaries of females ranging in age from prepubertal infant girl through to postmenopausal adulthood were obtained from immediate autopsy or after surgery. The results have revealed temporal and spatial changes in expression of aromatase at different stages of development. No immunoreactive aromatase was detected in the ovary of the 2.5 month infant. In premenopausal ovaries, aromatase was absent from the stromal compartment, but in follicles, a consistent pattern in expression of aromatase was observed, related to their size and developmental stage. Aromatase was not expressed in primordial, primary, or small secondary follicles less than 250 microns diameter. In slightly larger follicles (250-700 microns diameter) aromatase was first detected in a few thecal cells (TC). In more developed secondary through to large preovulatory follicles (greater than 1 cm) TC aromatase immunostain increased in intensity and number of positive cells, and the reaction was localized to a band of theca interna (TI) cells at the TI/theca externa interface. In granulosa cells (GC), aromatase was first detected in follicles in the initial stages of antrum formation (greater than 700 microns), and staining intensified as follicle diameter and antral cavity increased, being maximal in preovulatory follicles. GC aromatase was always found in the presence of TI immunostain. These two cell populations were separated by an unstained layer of TI cells giving the follicle walls a banded appearance. Immunostain was most intense in mural GC, was weaker in antral GC cells and was absent from the cumulus GC. Immunoreactive aromatase was also detected in functional corpora lutea (CL) but was absent from involuting CL's and corpora albicans. Our findings indicate that the immunostained cells of the CL are comprised of the former GC and possibly a subpopulation of former TI cells. In perimenopausal ovaries there was no evidence of any follicular or stromal aromatase immunostain. In postmenopausal ovaries no follicles were observed, but individual cells and clusters of cells in the stromal compartment of 3/7 specimens were found to have an aromatase immunostain reaction. In all cases, the aromatase immunostain reaction was cytoplasmic. The results provide the first direct evidence of the existence of TC aromatase, and of stromal cell aromatase in postmenopausal women.

Aromatase and other inhibitors in breast and prostatic cancer.

Estrogens have an important role in the growth of breast and other hormone-sensitive cancers. We have shown that 4-hydroxyandrostenedione (4-OHA) selectively blocks estrogen synthesis by inhibiting aromatase activity in ovarian and peripheral tissues and reduces plasma estrogen levels in rat and non-human primate species. In postmenopausal men and women, estrogens are mainly of peripheral origin. When postmenopausal breast cancer patients were administered either by daily oral or parenteral weekly treatment with 4-OHA, plasma estrogen concentrations were significantly reduced. Complete or partial response to treatment occurred in 34% of 100 patients with advanced breast cancer, while the disease was stabilized in 12%. We recently studied the effects of 4-OHA and other aromatase inhibitors, 10-propargylestr-4-ene-3,17-dione (PED) and imidazo[1,5-alpha]3,4,5,6-tetrahydropyrin-6-yl-(4-benzonitrile) (CGS 16949A) as well as 5 alpha-reductase inhibitors, N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxyamide (4-MA) and 17 beta-hydroxy-4-aza-4-methyl-19norandrost-5-en-3-one (L651190) in prostatic tissue from 11 patients with prostatic cancer and six patients with benign prostatic hypertrophy (BPH), and from normal men at autopsy. We attempted to measure aromatase activity in tissue incubation by quantitating 3H2O released during aromatization of androstenedione or testosterone labeled at the C-1 position. The amount of 3H2O released from all samples was at least twice that of the heat inactivated tissue samples. The 3H2O release was significantly inhibited by 4-OHA and 4-MA, but not by the other aromatase inhibitors. However, when HPLC and TLC were used to isolate steroid products, no estrone or estradiol was detected in the incubates. Furthermore, no aromatase mRNA was detected following amplification by PCR. The 4-OHA was found to inhibit 5 alpha-reductase in both BPH and cancer tissue, although to a lesser extent than 4-MA. The other aromatase inhibitors were without effect. Although a mechanism involving intraprostatic aromatase is not likely, inhibitors may act to reduce peripherally-formed estrogens. In postmenopausal breast cancer, the results indicate that 4-OHA is of significant benefit.

Aromatase inhibitors and hormone-dependent cancers.

Aromatase (estrogen synthetase) occurs in a variety of tissues. Using immunocytochemistry, we have recently located this enzyme in cellular compartments of several types of human tissue. Furthermore, we found the mRNA was located in the same structures where tested. As both gonadal and peripherally formed estrogen contribute to growth of hormone sensitive cancers, we have developed aromatase inhibitors to block synthesis of this hormone. We have determined that 4-hydroxyandrostenedione (4-OHA) selectively inhibits aromatase activity in ovarian and peripheral tissues and reduces plasma estrogen levels in rat and non-human primate species. 4-OHA was also found to inhibit gonadotropin levels and reduce estrogen and progesterone receptor levels in treated animals. The mechanism of these effects appear to be associated with the weak androgenic activity of the compound. These effects together with aromatase inhibition may result in a synergistic response reducing estrogen production and action. In postmenopausal women, estrogens are mainly of peripheral origin. When postmenopausal breast cancer patients were administered either daily oral or parenteral weekly treatment with 4-OHA at doses that did not affect their gonadotropin levels, plasma estrogen concentrations were significantly reduced. Complete or partial response to treatment occurred in 34% of 100 patients with advanced breast cancer, while the disease was stabilized in 12%. These results indicate that 4-OHA is of benefit in postmenopausal patients with advanced disease who have relapsed from prior hormonal therapies, and that steroidal inhibitors may be of value in premenopausal patients.

Lack of evidence for aromatase in human prostatic tissues: effects of 4-hydroxyandrostenedione and other inhibitors on androgen metabolism.

The effects of 4-hydroxyandrostenedione (4-OHA) and other aromatase inhibitors, 10-propargylestr-4-ene-3,17-dione and imidazo[1,5-alpha]-3,4,5,6-tetrahydropyrin-6-yl-(4-benzonitrile), as well as 5 alpha-reductase inhibitors N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxyamide and 4-methyl-3-oxo-4-aza-androsta-5-ene-17-ol were investigated in prostatic tissue from six patients with benign prostatic hypertrophy and seven patients with prostatic cancer, and from normal men at autopsy. We attempted to measure aromatase activity in the tissue incubations by quantitating 3H2O released from androstenedione or testosterone labeled at the C-1 position. High performance liquid chromatography and thin layer chromatography were used to isolate steroid products. Although the amount of 3H2O released was at least twice that of the heat-inactivated tissue samples, no estrone or estradiol was detected on high performance liquid chromatography. The 3H2O release was significantly inhibited by 4-OHA and N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxyamide, but not by the other aromatase inhibitors. 4-OHA also inhibited 5 alpha-reductase in both benign prostatic hypertrophy and cancer tissue, although to a lesser extent than N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxyamide. The other aromatase inhibitors were without effect on 5 alpha-reductase. Our results indicate that 3H2O released from [1 beta-3H]androstenedione and [1,2,6,7-3H]androstenedione does not correlate with estrogen formation and may be the result of other metabolic reactions. Although it appears that the prostate lacks aromatase, 4-OHA may be of benefit in patients with benign prostatic hypertrophy or prostatic cancer by inhibiting this enzyme in peripheral tissue.

Immunocytochemical studies of aromatase in early and full-term human placental tissues: comparison with biochemical assays.

An immunocytochemical method for visualizing the aromatase P450 enzyme with a specific monoclonal antibody has been developed for use with unfixed, frozen tissue sections. We compared both monoclonal and polyclonal aromatase-specific antibodies and found that placental aromatase was consistently and exclusively located in the syncytiotrophoblast layer of chorionic villi. The monoclonal antibody had the highest affinity, with negligible associated background stain. Fixation was found to impair stain reaction. Examination of first trimester and term placentae revealed identical immunostaining patterns of similar intensity in 9 of 10 samples. The immunostain reactions of first trimester and term placentae were compared with their respective microsomal aromatase activity, determined simultaneously by both indirect radiometric tritiated water (3H2O) assay, and direct product isolation by HPLC, using [1, 2, 6, 7(-3)H] androstenedione as substrate. The two assays were found to be comparable for enzyme activity estimates of term placental specimens. However, when first trimester specimens were analyzed, the direct-product measurements were significantly larger than the corresponding 3H2O assay results. Nonetheless, biochemical aromatase activity was found to correlate positively with immunostain reaction. Although 17 beta-hydroxysteroid dehydrogenase activity was not directly measured, differences in the estradiol:estrone product ratio (2.49 +/- 0.68 first trimester vs. 0.89 +/- 0.15 term) suggest differential control of this enzyme at the two stages of pregnancy. One first trimester specimen with an atypical, patchy immunostain distribution also had extremely low aromatase activity. The results indicate that both antibodies recognize functional aromatase enzyme and suggest that immunocytochemical detection is a sensitive, qualitative technique for investigating this important steroidogenic enzyme.

Increased responsiveness of the hypothalamic-pituitary axis to steroid feedback effects in ovariectomized rats treated neonatally with monosodium L-glutamate.

Chronic ovariectomized rats treated neonatally with MSG showed reduced circulating concentrations of LH coupled with elevated hypothalamic LHRH stores. Despite the apparent loss of LHRH secretion, the small pituitary glands showed an increased density of LHRH receptors and normal responsiveness to the releasing hormone. The positive feedback effects of progesterone on LH release in oestrogen-primed animals was greatly exaggerated reflecting the build-up of hypothalamic LHRH stores without loss of pituitary responsiveness to LHRH.

2-Hydroxyoestradiol acutely inhibits prolactin secretion from the superfused pituitary glands of normal female rats: evidence for a cyclical effect.

Catecholoestrogens are naturally occurring metabolites of oestrogens which are found in brain tissue and for which a neuroendocrine role has been postulated. However, reports of their effects on prolactin secretion are ambiguous and as yet no defined function has been attributed to them. The effects of 2-hydroxyoestradiol (2-OHE2) and dopamine on the release of prolactin in vitro by perfused pituitary glands from normal adult female rats at different stages of the oestrous cycle have been investigated. The purity and stability of the 2-OHE2 preparation before and after exposure to pituitary tissue was confirmed by radioenzymatic assay and subsequent thin-layer chromatography. Dopamine (500 nmol/l, 100 nmol/l) was found consistently to suppress release by 60%; this effect was immediate and reversible upon removal of the dopamine. In contrast, the effects of 2-OHE2 (10 nmol/l, 100 nmol/l) were found to vary during the cycle. No effect on prolactin release was evident during either dioestrus or pro-oestrus, but during oestrus a similar, though less potent, suppression of prolactin secretion to that of dopamine was observed (35% suppression compared with controls). The cyclical variation in the suppressive effect of 2-OHE2 on prolactin secretion in the female rat is compatible with a postulated neuroendocrine role for this catecholoestrogen.

Pituitary receptors for LH-releasing hormone (LHRH) and responsiveness to LHRH in adult female rats after neonatal monosodium L-glutamate treatment.

The effects of neonatal monosodium L-glutamate (MSG) treatment on pituitary responsiveness to LH-releasing hormone (LHRH) and on pituitary LHRH receptors have been investigated in the intact adult female rat. Three- to four-month-old rats treated with MSG (4 mg/g body wt) on days 2, 4, 6, 8 and 10 after birth had significantly reduced ovarian and pituitary weights, showed an absence or disruption of ovarian cyclicity after puberty, and had significantly higher concentrations of serum prolactin despite normal levels of LH. In-vitro pituitary LH responses to LHRH were in the normal range for one group of treated animals whilst in a second group the LH responses were markedly enhanced. In contrast, the total number of pituitary LHRH receptors were significantly reduced in all MSG-treated animals showing that the increased pituitary responsiveness of MSG-treated animals is not attributable to an increase in pituitary LHRH receptors.

Evidence for an increased opioid inhibition of LH secretion in hyperprolactinaemic ovariectomized rats.

The effects of acute and sub-chronic hyperprolactinaemia on the positive feedback action of progesterone in oestrogen-primed ovariectomized rats have been compared. A single injection of ovine prolactin administered with progesterone had no effect on the LH surge measured 5 h later although hyperprolactinaemia induced by 5-day treatment with the dopamine antagonist, domperidone, markedly attenuated the surge. Repeated injections of naloxone (5 mg/kg) during the development of the progesterone-stimulated LH surge completely reversed this inhibitory effect of hyperprolactinaemia, but had no apparent effect on the positive feedback action in control animals. In oestrogen-primed animals similar treatment with naloxone (0.4 and 5 mg/kg) stimulated LH secretion but the increase was significantly smaller than that observed after injecting progesterone. It is suggested that hyperprolactinaemia increases the inhibitory opioid modulation of LH release and that this effect is responsible for the impairment of the positive feedback action of progesterone.

Effects of 6-hydroxydopamine treatment of rats on the in-vitro release of LHRH and pituitary responsiveness to LHRH.

Injection of 150 micrograms 6-hydroxydopamine (6-OHDA) into the third ventricle of rats depleted the mean hypothalamic concentration of noradrenaline by 71% whereas the mean dopamine concentration was only reduced by an insignificant 7%. Isolated perfused pituitary glands taken from intact 6-OHDA-treated rats showed a markedly increased LH response to pulses of LHRH although there was no significant difference in the circulating levels of LH. Ovarian cyclicity was disrupted and the hypothalamic content of LHRH was significantly reduced. Hypothalamic synaptosomes prepared from intact 6-OHDA-treated animals consistently released less LHRH than did controls although the difference was not significant. Noradrenaline, dopamine and adrenaline did not significantly affect LHRH release from experimental or control synaptosome preparations. In ovariectomized rats 6-OHDA treatment did not inhibit the positive feedback effects of progesterone administration to oestrogen-primed animals, although the negative feedback effects of the priming oestrogen treatment was augmented. The results indicate that depletion of hypothalamic noradrenaline causes subtle changes in the endogenous release of LHRH and may alter the negative feedback effects of steroids on the hypothalamic-pituitary axis.