Marcella Motta

The luteinizing hormone-releasing hormone receptor in human prostate cancer cells: messenger ribonucleic acid expression, molecular size, and signal transduction pathway.

Evidence has accumulated indicating that LHRH might behave as an autocrine/paracrine growth inhibitory factor in some peripheral tumors. However, LHRH receptors in tumor cells have not been fully characterized, so far. The present experiments were performed to analyze: 1) the messenger RNA expression; 2) the molecular size; and 3) the signal transduction pathway of LHRH receptors in prostate cancer. For these studies, the human androgen-dependent LNCaP and androgen-independent DU 145 prostate cancer cell lines were used. 1) By RT-PCR, a complementary DNA product, which hybridized with a 32 P-labeled oligonucleotide probe specific for the pituitary LHRH receptor complementary DNA, was found both in LNCaP and in DU 145 cells. 2) Western blot analysis, using a monoclonal antibody raised against the human pituitary LHRH receptor, revealed the presence of a protein band of approximately 64 kDa (corresponding to the molecular mass of the pituitary receptor) in both cell lines. 3) In LNCaP and DU 145 cells, pertussis toxin completely abrogated the antiproliferative action of a LHRH agonist (LHRH-A). Moreover, LHRH-A substantially antagonized the pertussis toxin-catalyzed ADP-ribosylation of a Gai protein. Finally, LHRH-A significantly counteracted the forskolin-induced increase of intracellular cAMP levels in both cell lines. These data demonstrate that the LHRH receptor, which is present in prostate cancer cells, independently of whether they are androgen-dependent or not, corresponds to the pituitary receptor, in terms of messenger RNA expression and protein molecular size. However, at variance with the receptor of the gonadotrophs, prostate cancer LHRH receptor seems to be coupled to the Gai protein-cAMP signal transduction pathway, rather than to the Gaq/11-phospholipase C signaling system. This might be responsible for the different actions of LHRH in anterior pituitary and in prostate cancer. (Endocrinology 140: 5250 ‐5256, 1999)

The Androgen Derivative 5α-Androstane-3β,17β-Diol Inhibits Prostate Cancer Cell Migration Through Activation of the Estrogen Receptor β Subtype

Prostate cancer growth depends, in its earlier stages, on androgens and is usually pharmacologically modulated with androgen blockade. However, androgen-ablation therapy may generate androgen-independent prostate cancer, often characterized by an increased invasiveness. We have found that the 5alpha-reduced testosterone derivative, dihydrotestosterone (the most potent natural androgen) inhibits cell migration with an androgen receptor-independent mechanism. We have shown that the dihydrotestosterone metabolite 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), a steroid which does not bind androgen receptors, but efficiently binds the estrogen receptor beta (ERbeta), exerts a potent inhibition of prostate cancer cell migration through the activation of the ERbeta signaling. Very surprisingly, estradiol is not active, suggesting the existence of different pathways for ERbeta activation in prostate cancer cells. Moreover, 3beta-Adiol, through ERbeta, induces the expression of E-cadherin, a protein known to be capable of blocking metastasis formation in breast and prostate cancer cells. The inhibitory effects of 3beta-Adiol on prostate cancer cell migration is counteracted by short interfering RNA against E-cadherin. Altogether, the data showed that (a) circulating testosterone may act with estrogenic effects downstream in the catabolic process present in the prostate, and (b) that the estrogenic effect of testosterone derivatives (ERbeta-dependent) results in the inhibition of cell migration, although it is apparently different from that linked to estradiol on the same receptor and may be protective against prostate cancer invasion and metastasis. These results also shed some light on clinical observations suggesting that alterations in genes coding for 3beta-hydroxysteroid dehydrogenases (the enzymes responsible for 3beta-Adiol formation) are strongly correlated with hereditary prostate cancer.

Leptin: a possible link between food intake, energy expenditure, and reproductive function.

Several regulatory substances participate in the regulation of both food intake/energy metabolism and reproduction in mammals. Most of these neuropeptides originate and act in the central nervous system, mainly at specific hypothalamic areas. Leptin represents a signal integrating all these functions, but originating from the periphery (adipose tissue) and carrying information mainly to central structures. Observations in rodent models of leptin deficiency have suggested that leptin participates in the control of reproduction, in conjunction with that of food intake and energy expenditure. Indeed, leptin administration resulted in the restoration of normal body weight, food intake, and fertility in the ob mouse, lacking circulating leptin. Specific targets of leptin in the hypothalamus are neurons expressing neuropeptide Y, proopiomelanocortin and gonadotropin-releasing hormone, but the presence of leptin receptors in peripheral reproductive structures suggests that leptin might also act at these sites. Human obesity is often associated with reproductive disturbances. The situation in humans is more complex than in the animal models of leptin deficit and the presence of leptin resistance in these subjects is suggested. In conclusion, leptin fits many requirements for a molecule linking the regulation of energy balance and the control of reproduction.

Presence of 5α‐Reductase isozymes and aromatase in human prostate cancer cells and in benign prostate hyperplastic tissue

Prostate trophism depends on DHT formed from T by the enzyme 5α‐R. Two 5α‐R isoforms with different biochemical characteristics have been cloned. Also estrogens might contribute to the prostate growth; however, their intraglandular formation by the enzyme aromatase is still debated. The aim of the present study was to verify whether (a) only one or both isoforms of the 5α‐Rs are expressed in the prostate cancer cell line LNCaP and in BPH, or (b) the aromatase is present in these samples.

The androgen derivative 5alpha-androstane-3beta,17beta-diol inhibits prostate cancer cell migration through activation of the estrogen receptor beta subtype.

Prostate cancer growth depends, in its earlier stages, on androgens and is usually pharmacologically modulated with androgen blockade. However, androgen-ablation therapy may generate androgen-independent prostate cancer, often characterized by an increased invasiveness. We have found that the 5alpha-reduced testosterone derivative, dihydrotestosterone (the most potent natural androgen) inhibits cell migration with an androgen receptor-independent mechanism. We have shown that the dihydrotestosterone metabolite 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), a steroid which does not bind androgen receptors, but efficiently binds the estrogen receptor beta (ERbeta), exerts a potent inhibition of prostate cancer cell migration through the activation of the ERbeta signaling. Very surprisingly, estradiol is not active, suggesting the existence of different pathways for ERbeta activation in prostate cancer cells. Moreover, 3beta-Adiol, through ERbeta, induces the expression of E-cadherin, a protein known to be capable of blocking metastasis formation in breast and prostate cancer cells. The inhibitory effects of 3beta-Adiol on prostate cancer cell migration is counteracted by short interfering RNA against E-cadherin. Altogether, the data showed that (a) circulating testosterone may act with estrogenic effects downstream in the catabolic process present in the prostate, and (b) that the estrogenic effect of testosterone derivatives (ERbeta-dependent) results in the inhibition of cell migration, although it is apparently different from that linked to estradiol on the same receptor and may be protective against prostate cancer invasion and metastasis. These results also shed some light on clinical observations suggesting that alterations in genes coding for 3beta-hydroxysteroid dehydrogenases (the enzymes responsible for 3beta-Adiol formation) are strongly correlated with hereditary prostate cancer.

Free and bound plasma leptin in normal weight and obese men and women: relationship with body composition, resting energy expenditure, insulin-sensitivity, lipid profile and macronutrient preference.

Objective  The adipose‐borne hormone leptin circulates in free and protein‐bound forms but little information is available about their biological significance. Free leptin (FL) levels are related to changes in fat mass, whereas bound leptin (BL) appears to be associated with resting energy expenditure (REE). Our aim was to assess FL and BL levels in normal weight and obese subjects and correlate them with metabolic and nutritional variables.

Luteinizing hormone-releasing hormone agonists interfere with the mitogenic activity of the insulin-like growth factor system in androgen-independent prostate cancer cells

We have previously shown that LHRH agonists exert a direct and specific inhibitory action on the proliferation of the androgen-independent DU 145 prostate cancer cell line; however, the cellular mechanisms mediating this antiproliferative action are not well defined. It is well known that the insulin-like growth factor (IGF) system plays a crucial role in the local regulation of the growth of androgen-independent prostate cancer. The present experiments were performed to evaluate whether LHRH agonists might exert their antimitogenic effect by interfering with the activity of the locally expressed IGF system. To this purpose, the effects of the LHRH agonist Zoladex (LHRH-A) on 1) the mitogenic action of IGF-I, 2) the tyrosine phosphorylation of type 1 IGF-I receptor (IGF-IR), 3) the concentration of IGF-IR, and 4) the secretion of IGF-binding protein-3 were studied. The results obtained show that in DU 145 cells, LHRH-A 1) counteracts the mitogenic action of IGF-I in a dose-dependent manner, 2) prevents th...

Endocrine Effects of Pineal Gland and of Melatonin

Summary 1. Pinealectomy when performed in male rats results in a significant increase in weight of the testes, the prostates and the seminal vesicles. This suggests that the pineal gland usually inhibits the secretion of LH and of FSH. 2. Melatonin administered to male rats diminishes the weights of prostates and of seminal vesicles, but does not change testicular weight, indicating that exogenous melatonin suppresses the secretion of LH, but does not interfere with FSH release. 3. In prepuberal female rats melatonin retards puberty and decreases pituitary weight as well as the weights of the ovaries and the uteri, confirming that melatonin reduces LH secretion. 4. It is suggested that the pineal gland exerts an anti-FSH effect through compounds different from melatonin.

Estrogen receptor beta (ERbeta) and inhibition of prostate cancer cell proliferation : studies on the possible mechanism of action in DU145 cells

Estrogen receptor beta (ERbeta) plays a protective role against uncontrolled cell proliferation. ERbeta is lost during prostate cancer (CaP) progression suggesting its direct involvement in contrasting tumor proliferation in this disease; however, the molecular mechanism at the basis of this effect has not been clearly defined yet. Possible molecular targets of ERbeta were assessed in DU145 cells, a CaP cell line expressing only ERbeta. Cells treated from 1 to 9 days with different doses of estradiol or diarylpropionitrile (DPN, an ERbeta-selective agonist) show a time-dependent decrease in cell proliferation. The reduced proliferation rate is accompanied by the stimulation of ERbeta expression and the increase of cyclin-dependent kinase inhibitor p21. We demonstrate that the endogenous ERbeta is one of the mediator of the antiproliferative action of estrogens enhancing the synthesis of molecules such as p21 that control cell cycle, an effect amplified by the autoregulation of ERbeta expression. Our observations suggest that CaP, when expressing a functional ERbeta, might be sensitive to the antiproliferative action of estrogens; therefore, ERbeta specific agonists might be valid candidates for new pharmacological approaches to this disease.

Growth-Inhibitory Activity of Melatonin on Human Androgen-Independent DU 145 Prostate Cancer Cells

The pineal hormone melatonin has been shown to exert a direct oncostatic activity on neoplastic cells, particularly from breast cancer. In the present study, we evaluated the effects of melatonin on the proliferation and on the cell cycle distribution of human androgen‐independent DU 145 prostate cancer cells. Experiments were also performed to gain insights into the possible mechanism of action of the hormone.