Autocrine role of gonadotropin-releasing hormone and its receptor in ovarian cancer cell growth

Role of gonadotropin-releasing hormone 2 and its receptor in human reproductive cancers

Gonadotropin-releasing hormone (GnRH1) and its receptor (GnRHR1) drive reproduction by regulating gonadotropins. Another form, GnRH2, and its receptor (GnRHR2), also exist in mammals. In humans, GnRH2 and GnRHR2 genes are present, but coding errors in the GnRHR2 gene are predicted to hinder full-length protein production. Nonetheless, mounting evidence supports the presence of a functional GnRHR2 in humans. GnRH2 and its receptor have been identified throughout the body, including peripheral reproductive tissues like the ovary, uterus, breast, and prostate. In addition, GnRH2 and its receptor have been detected in a wide number of reproductive cancer cells in humans. Notably, GnRH2 analogues have potent anti-proliferative, pro-apoptotic, and/or anti-metastatic effects on various reproductive cancers, including endometrial, breast, placental, ovarian, and prostate. Thus, GnRH2 is an emerging target to treat human reproductive cancers.

EGF-Enhanced GnRH-II Regulation in Decidual Stromal Cell Motility through Twist and N-Cadherin Signaling

Crucial roles in embryo implantation and placentation in humans include the invasion of the maternal decidua by extravillous trophoblasts and the motile behavior of decidual endometrial stromal cells. The effects of the epidermal growth factor (EGF) and GnRH-II in the endometrium take part in early pregnancy. In the present study, we demonstrated the coaction of EGF- and GnRH-II-promoted motility of human decidual endometrial stromal cells, indicating the possible roles of EGF and GnRH-II in embryo implantation and early pregnancy. After obtaining informed consent, we obtained human decidual endometrial stromal cells from decidual tissues from normal pregnancies at 6 to 12 weeks of gestation in healthy women undergoing suction dilation and curettage. Cell motility was evaluated with invasion and migration assays. The mechanisms of EGF and GnRH-II were performed using real-time PCR and immunoblot analysis. The results showed that human decidual tissue and stromal cells expressed the EGF and GnRH-I receptors. GnRH-II-mediated cell motility was enhanced by EGF and was suppressed by the knockdown of the endogenous GnRH-I receptor and EGF receptor with siRNA, revealing that GnRH-II promoted the cell motility of human decidual endometrial stromal cells through the GnRH-I receptor and the activation of Twist and N-cadherin signaling. This new concept regarding the coaction of EGF- and GnRH-promoted cell motility suggests that EGF and GnRH-II potentially affect embryo implantation and the decidual programming of human pregnancy.

Short-term but not long-term high-fat diet induces an increase in gene expression of gonadotropic hormones and GPR120 in the male mouse pituitary gland

High-fat diet (HFD) is associated with the regulation of reproductive functions. This study aimed to investigate the effects of short-term HFD on the mRNA expression levels of follicle-stimulating hormone β subunit (FSHβ), luteinizing hormone β subunit (LHβ), gonadotropin-releasing hormone receptor, and long-chain fatty acid receptor, GPR120, in the matured male mouse pituitary gland. Adult male mice were fed either control chow or HFD for 1, 2, 5, 10, 30 and 150 days. Fshb and Gpr120 mRNA expression levels in the pituitary glands were significantly increased during 2 to 30 days of HFD feeding. Gnrh-r mRNA in the 30 days HFD fed group and body weight in the 30 and 150 days HFD fed groups were higher than control. However, there were no significant differences in plasma non-esterified fatty acids or glucose levels during the 150 days of HFD feeding. These results suggest that male mice feeding a short-term HFD induces FSHβ synthesis and GPR120 expression in their pituitary gonadotropes.

Elucidating the genetic architecture of reproductive ageing in the Japanese population

Population studies elucidating the genetic architecture of reproductive ageing have been largely limited to European ancestries, restricting the generalizability of the findings and overlooking possible key genes poorly captured by common European genetic variation. Here, we report 26 loci (all P < 5 × 10^–8) for reproductive ageing, i.e. puberty timing or age at menopause, in a non-European population (up to 67,029 women of Japanese ancestry). Highlighted genes for menopause include GNRH1, which supports a primary, rather than passive, role for hypothalamic-pituitary GnRH signalling in the timing of menopause. For puberty timing, we demonstrate an aetiological role for receptor-like protein tyrosine phosphatases by combining evidence across population genetics and pre- and peri-pubertal changes in hypothalamic gene expression in rodent and primate models. Furthermore, our findings demonstrate widespread differences in allele frequencies and effect estimates between Japanese and European associated variants, highlighting the benefits and challenges of large-scale trans-ethnic approaches.

The timing of female reproductive capacity is influenced by genetic and environmental factors. Here, in genome-wide association studies, the authors identify genetic loci for age at menarche and onset of menopause in Japanese women, and highlight differences with European populations.

Augmentation of gonadotropin-releasing hormone receptor expression in the post-lactational mammary tissues of rats

Gonadotropin-releasing hormone (GnRH) is a neurohormone of the hypothalamus controlling pituitary gonadotropin secretion and hence gametogenesis. While it has also been believed that GnRH is synthesized and functions in various peripheral tissues, the expression of GnRH receptor (GnRH-R) in peripheral tissues is not well-described. We previously found that annexin A5, which is increased in the pituitary gonadotropes by GnRH, is dramatically increased in rat mammary epithelial cells after weaning, suggesting that local GnRH is responsible for this increase. Annexin A5 is a member of the annexin family of proteins and is thought to be involved in various regulatory mechanisms, including apoptosis. In the present study, we examined GnRH-R expression in the mammary tissues after weaning. Although GnRH-R mRNA was not detected in the mammary tissues during lactation, it was dramatically increased after weaning. Forced weaning at mid-lactation (day 10) also promoted the expression of GnRH-R transcripts in mammary tissues within 2 days. Furthermore, western blotting analysis with anti-GnRH-R showed that the expression of an immuno-positive 60-kDa protein, whose size was equivalent to that of rat GnRH-R, was confirmed to increase after weaning. These findings clarified the induction of GnRH-R in the mammary tissues after weaning and suggest that GnRH is involved in the involution and tissue remodeling of post-lactating rat mammary tissues.

Effects of GnRH agonists on the expression of developmental follicular anti-mullerian hormone in varying follicular stages in cyclic mice in vivo

Gonadotrophin‑releasing hormone (GnRH) agonists (GnRHa) have been widely used to induce a state of downregulation for in vitro fertilization, and its direct effects on the pituitary are well known. However, the effects of GnRHa on the expression of anti‑mullerian hormone (AMH) by follicles in varying stages in vivo remain to be fully elucidated. In the present study 84 cyclic mice were randomly divided equally into four GnRHa groups and three cyclic mice were used as a control group. The expression levels of AMH in follicles of varying stages between days 0 and 7 following GnRHa administration were quantified using immunohistochemistry. The expression of AMH in follicles at various stages revealed dynamic changes during the process of downregulation. AMH in primary follicles initially increased and then decreased gradually. In small and large preantral follicles and in granulosa cells (GCs) surrounding the oocyte of small antral follicles, the expression of AMH began to increase on day 1, was attenuated on day 2, and then increased to a peak. The expression levels of AMH in the GCs surrounding the basement membrane, in contrast to the GCs surrounding the oocyte, were significantly lower and did not increase on day 1. In all stages of follicles, the expression of AMH declined gradually between the peak level and last day of downregulation. On day 7, the varying follicular stages all expressed lower levels of AMH than on day 0. This decrease was more prominent in the higher dose groups, compared with the lower dose groups. In conclusion, GnRHa was observed to induce time‑dependent changes in the expression of AMH at varying follicular stages, which occurred in a dose‑dependent manner.

OCT4 mediates FSH-induced epithelial-mesenchymal transition and invasion through the ERK1/2 signaling pathway in epithelial ovarian cancer

Our previous study showed that Octamer-binding transcription factor 4 (OCT4) expression was upregulated and significantly associated with histological grade through the analysis of OCT4 expression in 159 ovarian cancer tissue samples, and OCT4 mediated follicle-stimulating hormone (FSH)-induced anti-apoptosis in epithelial ovarian cancer. Nevertheless, whether OCT4 participates in FSH-induced invasion in ovarian cancer is still unknown. Therefore, the present study aimed to define whether FSH-induced ovarian cancer invasion is mediated by OCT4. In present study, we showed that FSH induced not only the epithelial-mesenchymal transition (EMT) and invasive phenotype but also the upregulation of OCT4 expression in a dose- and time-dependent manner in epithelial ovarian cancer cells. In addition, the expression of FSH receptor (FSHR) was upregulated by FSH induction, and knockdown of FSHR inhibited FSH-stimulated OCT4 expression. ERK1/2 signaling pathway participated in the enhanced expression of OCT4 and Snail induced by FSH. We further showed that the activated expression of Snail and N-cadherin, the suppressed expression of E-cadherin and the morphological change of the cells stimulated by FSH were blocked by OCT4-specific small interfering RNA. Moreover, our results showed that OCT4 mediated the increase in invasive capacity induced by FSH in ovarian cancer cells. Taken together, our work reveals that OCT4 is an essential mediator in FSH-induced EMT and invasion in epithelial ovarian cancer and may act as a potential therapeutic target.

Influence of gonadotropin-releasing hormone agonist on the effect of chemotherapy upon ovarian cancer and the prevention of chemotherapy-induced ovarian damage: an experimental study with nu/nu athymic mice

BACKGROUND AND OBJECTIVE

Gonadotropin-releasing hormone (GnRH) plays an important role in the regulation of ovarian function and ovarian cancer cell growth. In this study, we determined whether administration of the GnRH agonist (GnRHa), triporelin, prior to cisplatin treatment affects cisplatin and/or prevents cisplatin-induced ovarian damage.

METHODS

nu/nu mice were injected with ovarian cancer OVCAR-3 cells intraperitoneally. After two weeks, the mice were treated with saline (control), cisplatin, GnRHa, or cisplatin plus GnRHa for four weeks. At the end of the experimental protocol, blood, tumor, ovary, and uterine tissues were resected for hematoxylin and eosin (H&E) staining, immunohistochemical analyses of Ki67, nuclear factor-κB (NF-κB), and caspase-3, transmission electron microscopy of apoptosis, or enzyme-linked immunosorbent assay (ELISA) analyses of anti-Mullerian hormone (AMH).

RESULTS

Cisplatin treatment effectively inhibited tumor growth in mice treated with human ovarian cancer cells; however the treatment also induced considerable toxicity. Immunohistochemical analyses showed that Ki67 expression was reduced in cisplatin-treated mice compared to control (P<0.05), but there was no statistically significant differences between cisplatin-treated mice and cisplatin plus GnRHa-treated mice (P>0.05), while expressions of NF-κB and caspase-3 were reduced and induced, respectively, in cisplatin-treated mice and cisplatin plus GnRHa-treated mice. Apoptosis occurred in the GnRHa, cisplatin, and cisplatin plus GnRHa-treated mice, but not in control mice. Ovaries exposed to GnRHa in both GnRHa mice and cisplatin-treated mice (combination group) had significantly more primordial and growth follicles and serum levels of AMH than those in the control mice and cisplatin-treated mice (P<0.05).

CONCLUSIONS

Administration of GnRHa to mice significantly decreased the extent of ovarian damage induced by cisplatin, but did not affect the anti-tumor activity of cisplatin.

Gonadotropin-releasing hormone type II (GnRH-II) agonist regulates the invasiveness of endometrial cancer cells through the GnRH-I receptor and mitogen-activated protein kinase (MAPK)-dependent activation of matrix metalloproteinase (MMP)-2

Background

More than 25% of patients diagnosed with endometrial carcinoma have an invasive primary cancer accompanied by metastases. Gonadotropin-releasing hormone (GnRH) plays an important role in reproduction. In mammals, expression of GnRH-II is higher than GnRH-I in reproductive tissues. Here, we examined the effect of a GnRH-II agonist on the motility of endometrial cancer cells and its mechanism of action in endometrial cancer therapy.

Methods

Immunoblotting and immunohistochemistry (IHC) were used to determine the expression of the GnRH-I receptor protein in human endometrial cancer. The activity of MMP-2 in the conditioned medium was determined by gelatin zymography. Cell motility was assessed by invasion and migration assay. GnRH-I receptor si-RNA was applied to knockdown GnRH-I receptor.

Results

The GnRH-I receptor was expressed in the endometrial cancer cells. The GnRH-II agonist promoted cell motility in a dose-dependent manner. The GnRH-II agonist induced the phosphorylation of ERK1/2 and JNK, and the phosphorylation was abolished by ERK1/2 inhibitor (U0126) and the JNK inhibitor (SP600125). Cell motility promoted by GnRH-II agonist was suppressed in cells that were pretreated with U0126 and SP600125. Moreover, U0126 and SP600125 abolished the GnRH-II agonist-induced activation of MMP-2. The inhibition of MMP-2 with MMP-2 inhibitor (OA-Hy) suppressed the increase in cell motility in response to the GnRH-II agonist. Enhanced cell motility mediated by GnRH-II agonist was also suppressed by the knockdown of the endogenous GnRH-I receptor using siRNA.

Conclusion

Our study indicates that GnRH-II agonist promoted cell motility of endometrial cancer cells through the GnRH-I receptor via the phosphorylation of ERK1/2 and JNK, and the subsequent, MAPK-dependent activation of MMP-2. Our findings represent a new concept regarding the mechanism of GnRH-II-induced cell motility in endometrial cancer cells and suggest the possibility of exploring GnRH-II as a potential therapeutic target for the treatment of human endometrial cancer.

GnRH receptors in cancer: from cell biology to novel targeted therapeutic strategies

The crucial role of pituitary GnRH receptors (GnRH-R) in the control of reproductive functions is well established. These receptors are the target of GnRH agonists (through receptor desensitization) and antagonists (through receptor blockade) for the treatment of steroid-dependent pathologies, including hormone-dependent tumors. It has also become increasingly clear that GnRH-R are expressed in cancer tissues, either related (i.e. prostate, breast, endometrial, and ovarian cancers) or unrelated (i.e. melanoma, glioblastoma, lung, and pancreatic cancers) to the reproductive system. In hormone-related tumors, GnRH-R appear to be expressed even when the tumor has escaped steroid dependence (such as castration-resistant prostate cancer). These receptors are coupled to a G(αi)-mediated intracellular signaling pathway. Activation of tumor GnRH-R by means of GnRH agonists elicits a strong antiproliferative, antimetastatic, and antiangiogenic (more recently demonstrated) activity. Interestingly, GnRH antagonists have also been shown to elicit a direct antitumor effect; thus, these compounds behave as antagonists of GnRH-R at the pituitary level and as agonists of the same receptors expressed in tumors. According to the ligand-induced selective-signaling theory, GnRH-R might assume various conformations, endowed with different activities for GnRH analogs and with different intracellular signaling pathways, according to the cell context. Based on these consistent experimental observations, tumor GnRH-R are now considered a very interesting candidate for novel molecular, GnRH analog-based, targeted strategies for the treatment of tumors expressing these receptors. These agents include GnRH agonists and antagonists, GnRH analog-based cytotoxic (i.e. doxorubicin) or nutraceutic (i.e. curcumin) hybrids, and GnRH-R-targeted nanoparticles delivering anticancer compounds.

Revisiting the role of antiandrogen strategies in ovarian cancer

Androgen receptors are frequently expressed in epithelial ovarian cancer (EOC). Their role in the development of EOC is not fully understood. In the present review we first discuss the epidemiological data linking a hyperandrogen state to a higher risk for ovarian cancer, second describe in vitro studies of the role of androgens in influencing the growth of EOC, and finally review the completed clinical trials with compounds that exploit the androgen axis in patients with ovarian cancer. The therapeutic approaches that inhibit androgen signaling have so far produced only modest response rates. In the light of new data regarding the role of androgen stimulation in the evolution of EOC and the emergence of new compounds used for the treatment of other hormone-driven malignancies, such as prostate and breast cancer, we provide suggestions for new studies of antiandrogen therapeutics in the treatment of EOC. A specific example is the new agent abiraterone. In addition, we propose a panel of molecules that could be assessed as potential biomarkers that may aid patient selection for this approach in the future.

Cadherin switching and activation of p120 catenin signaling are mediators of gonadotropin-releasing hormone to promote tumor cell migration and invasion in ovarian cancer

Gonadotropin-releasing hormone (GnRH) receptor expression is often elevated in ovarian cancer, but its potential role in ovarian cancer metastasis has just begun to be revealed. Cadherin switching is a crucial step during tumorigenesis, particularly in metastasis. Here, we showed that GnRH is an inducer of E- to P-cadherin switching, which is reminiscent of that seen during ovarian tumor progression. Overexpression of P-cadherin significantly enhanced, whereas knockdown of P-cadherin reduced migration and invasion regardless of E-cadherin expression, suggesting that inappropriate expression of P-cadherin contributes to the invasive phenotype. These effects of P-cadherin were mediated by activation of the Rho GTPases, Rac1, and Cdc42, through accumulation of p120 catenin (p120(ctn)) in the cytoplasm. The use of p120(ctn) small interfering RNA or chimeric cadherin construct to inhibit p120(ctn) expression and cytoplasmic localization, respectively, resulted in significant inhibition of cell migration and invasion, with a concomitant reduction in Rac1 and Cdc42 activation, confirming that the effect was p120(ctn) specific. Similarly, the migratory/invasive phenotype could be reversed by expression of dominant-negative Rac1 and Cdc42. These results identify for the first time cadherin switching and p120(ctn) signaling as important targets of GnRH function and as novel mediators of invasiveness and tumor progression in ovarian cancer.

GnRH signaling in intrauterine tissues

Type I GnRH (GnRH-I, GNRH1) and type II GnRH (GnRH-II, GNRH2), each encoded by separate genes, have been identified in humans. The tissue distribution and functional regulation of GnRH-I and GnRH-II clearly differ despite their comparable cDNA and genomic structures. These hormones exert their effects by binding to cell surface transmembrane G protein coupled receptors and stimulating the Gq/11 subfamily of G proteins. The hypothalamus and pituitary are the main origin and target sites of GnRH, but numerous studies have demonstrated that extra-hypothalamic GnRH and extra-pituitary GnRH receptors exist in different reproductive tissues such as the ovary, endometrium, placenta, and endometrial cancer cells. In addition to endocrine regulation, GnRH is also known to act in an autocrine and paracrine manner to suppress cell proliferation and activate apoptosis in the endometrium and endometrial cancer cells through several mechanisms. Both GnRH-I and GnRH-II exhibit regulatory roles in tissue remodelling during embryo implantation and placentation, which suggests that these hormones may have important roles in embryo implantation and early pregnancy. The presence of varied GnRH and GnRH receptor systems demonstrate their different roles in distinct tissues using dissimilar mechanisms. These may result in the generation of new GnRH analogues used for several hormone-related diseases.

Gonadotropin-releasing hormone: GnRH receptor signaling in extrapituitary tissues

Gonadotropin-releasing hormone (GnRH) has historically been known as a pituitary hormone; however, in the past few years, interest has been raised in locally produced, extrapituitary GnRH. GnRH receptor (GnRHR) was found to be expressed in normal human reproductive tissues (e.g. breast, endometrium, ovary, and prostate) and tumors derived from these tissues. Numerous studies have provided evidence for a role of GnRH in cell proliferation. More recently, we and others have reported a novel role for GnRH in other aspects of tumor progression, such as metastasis and angiogenesis. The multiple actions of GnRH could be linked to the divergence of signaling pathways that are activated by GnRHR. Recent observations also demonstrate cross-talk between GnRHR and growth factor receptors. Intriguingly, the classical G(alphaq)-11-phospholipase C signal transduction pathway, known to function in pituitary gonadotropes, is not involved in GnRH actions at nonpituitary targets. Herein, we review the key findings on the role of GnRH in the control of tumor growth, progression, and dissemination. The emerging role of GnRHR in actin cytoskeleton remodeling (small Rho GTPases), expression and/or activity of adhesion molecules (integrins), proteolytic enzymes (matrix metalloproteinases) and angiogenic factors is explored. The signal transduction mechanisms of GnRHR in mediating these activities is described. Finally, we discuss how a common GnRHR may mediate different, even opposite, responses to GnRH in the same tissue/cell type and whether an additional receptor(s) for GnRH exists.

Gonadotropin-releasing hormone (GnRH) and its receptor in human meningiomas

OBJECTIVE

Meningiomas are the most common neoplasms of the central nervous system and are more frequent in women than in men. Many studies have been conducted to determine whether the progesterone receptor (PR) and estrogen receptor (ER) are present or absent in meningiomas. No previous studies, however, have investigated the status (presence or absence) of gonadotropin-releasing hormone (GnRH) and its receptor (GnRH-R), two major factors related to PR and ER, in meningiomas. This study aims to determine the status of GnRH and GnRH-R and to elucidate the correlations of GnRH and GnRH-R with PR, ER, and clinical features in meningiomas.

METHODS

Eighty-two specimens of human meningiomas were obtained for immunohistochemical analysis with anti-GnRH, anti-GnRH-R, anti-PR, anti-ER, and anti-Ki-67 (MIB-1) antibodies, and for RT-PCR analysis of the mRNA expressions of GnRH and GnRH-R. Correlations of GnRH and GnRH-R with PR, ER, Ki-67, and clinical features such as age, sex, tumor grade, and tumor histology were assessed.

RESULTS

Seventy-eight (95.1%) of the 82 meningiomas reacted positively in the cytoplasm for the GnRH-R. Forty-nine (59.8%) of the 82 cases reacted positively in the cytoplasm for the GnRH. The positive immunoreactivity for GnRH-R and GnRH was confirmed by the RT-PCR analyses of mRNA. Forty-seven (96%) of the 49 cases with positive immunoreactivity for GnRH-R also had positive immunoreactivity for GnRH. PR expression was higher in the tumors positive for GnRH-R (p=0.002), and a significantly higher proportion of tumors from male patients exhibited positive immunoreactivity for GnRH (p=0.02). No significant correlations were found between the status of GnRH-R or GnRH with other clinicopathological features.

CONCLUSION

Over half of meningiomas may be regulated by GnRH-GnRH-R expression in an autocrine fashion. This unique expression profile of GnRH and GnRH-R may open the way to the development of GnRH analogs as a treatment tool in the future.

[Chemoprevention and prophylactic surgery in ovarian carcinoma]

INTRODUCTION

Ovarian cancer is the leading cause of death from gynaecological malignancy, especially because of late diagnosis. The objective of the study was to provide the clinician with current concepts regarding prevention of ovarian cancer.

MATERIAL AND METHODS

A computerized search of articles published was performed using the Medline database We performed a review of the literature (PubMed, Embase) using the following search terms (MeSH and non-MeSH): prevention, chemoprevention, chemoprevention, ovarian cancer, ovarian, ovary, carcinoma, tumor, tumour.

RESULTS

Oral contraceptive and acetaminophen use may provide substantial protection against ovarian cancer, whereas aspirin, carotenoids and non-steroidal anti-inflammatory agents do not decrease the risk. However, to date, there is no recommendation concerning low risk population. At the opposite, young women (<35-40 years old) presenting with BRCA1 or 2 mutation or Lynch syndrome may be counseled for chemoprevention using oral contraceptive. For high risk women over 35-40 years old, prophylactic bilateral salpingo-oophorectomy should be performed. Indeed, it has been showed that prophylactic surgery significantly decrease mortality rates in high risk women.

CONCLUSION

Large randomized studies are required to assess the efficacy of ovarian cancer chemoprevention in low risk women. High-risk women over 35-40 years old should be counseled for prophylactic salpingo-oophorectomy or for chemoprevention using oral contraceptive.

Luteinising hormone-releasing hormone antagonists in prostate cancer therapy

The introduction of androgen blockade therapy using luteinising hormone-releasing hormone (LHRH)/gonadotropin-releasing hormone analogues alone or in combination with non-steroidal antiandrogens has a major impact in both survival and quality of life of patients with locally advanced and metastatic prostate cancer. The effect of LHRH agonists is based on the continuous binding to the LHRH receptor (LHRH-R) on the gonadotrope cells of the pituitary, which although initially stimulate LH release, consequently downregulates the LHRH-R, thereby suppressing serum LH, testosterone levels and 5alpha-dihydrotestosterone levels. Because this initial surge of LH and testosterone can cause adverse consequences in these patients (the so-called flare-up symptoms), immediate inhibition of LH release and testosterone production is desirable and this can be achieved with the use of the LHRH antagonists. In addition, there exist data to support a direct anticancer effect of LHRH antagonists on prostate cancer cells. This review summarises the potential clinical use of the LHRH antagonists in prostate cancer patients.

Differential role of gonadotropin-releasing hormone on human ovarian epithelial cancer cell invasion

Ovarian cancer is the most lethal of all gynecological cancers. Most deaths from ovarian cancer are due to widespread intraperitoneal metastases and malignant ascites. However, mechanisms of invasion in ovarian cancer remain poorly understood. In this study, we examined the effects of gonadotropin-releasing hormone (GnRH)-I (the classical mammalian GnRH), GnRH-II (a second form of GnRH), and GnRH receptor on invasion using two human ovarian carcinoma cell lines, OVCAR-3 and SKOV-3. Here we demonstrated that in OVCAR-3, GnRH-I and GnRH-II promoted cell invasion, whereas in SKOV-3, GnRH-I and GnRH-II inhibited cell invasion. Transfection of small interfering RNA to abrogate the gene expression of GnRH receptor reversed GnRH-I and GnRH-II-mediated invasion activities, suggesting that the same receptor, type I GnRH receptor, is essential for the effects of GnRH-I and GnRH-II in both OVCAR-3 and SKOV-3. Treatment of SKOV-3 cells with GnRH-I or GnRH-II resulted in a decrease in matrix metalloproteinase 2 but an increase in tissue inhibitor of metalloproteinase 2 secretions. In addition, we found that GnRH-I and GnRH-II interfered with activation of the phosphatidylinositol-3-kinase/AKT pathway that is well documented to stimulate proteolysis and invasion of ovarian cancer cells. Taken together, these observations suggest that GnRH-I and GnRH-II play key regulatory roles in ovarian tumor cell invasion and extracellular matrix degradation.

Hormonal therapy in ovarian cancer

Ovarian carcinoma continues to be the leading cause of death due to gynecological malignancy. Epidemiologic studies indicate that steroid hormones play roles in ovarian carcinogenesis. Gonadotropins, estrogen, and androgen may be causative factors, while gonadotropin-releasing hormone and progesterone may be protective factors in ovarian cancer pathogenesis. Experimental studies have shown that hormonal receptors are expressed in ovarian cancer cells and mediate the growth-stimulatory or growth-inhibitory effects of the hormones on these cells. Hormonal therapeutic agents have been evaluated in several clinical trials. Most of these trials were conducted in patients with recurrent or refractory ovarian cancer, with modest efficacy and few side effects. Better understanding of the mechanisms through which hormones affect cell growth may improve the efficacy of hormonal therapy. Molecular markers that can reliably predict major clinical outcomes should be investigated further in well-designed trials.

Gonadotropin-releasing hormone promotes ovarian cancer cell invasiveness through c-Jun NH2-terminal kinase-mediated activation of matrix metalloproteinase (MMP)-2 and MMP-9

Gonadotropin-releasing hormone (GnRH) receptor is present in 80% of ovarian cancer, and numerous studies have provided evidence for a role of GnRH in cell proliferation. In this study, the effect of GnRH on the invasion potential of ovarian cancer cells was investigated. In vitro migration and cell invasion assays with the ovarian cancer cell lines Caov-3 and OVCAR-3 revealed the biphasic nature of GnRH; low concentrations of GnRH agonist (GnRHa) increased the cell motility and invasiveness of these cells, but at increased concentrations, the stimulatory effect was insignificant. Reverse transcription-PCR, Western blot, and gelatin zymography showed that the expression of metastasis-related proteinases, matrix metalloproteinase (MMP)-2 and MMP-9, was up-regulated and activated by GnRHa. Moreover, we observed that GnRHa was able to transactivate the MMP-2 and MMP-9 promoters. The invasive/migratory phenotype activated by GnRHa can be blocked by specific inhibitors or neutralizing antibodies to MMP-2 and MMP-9. Knockdown of the GnRH receptor using small interfering RNA significantly inhibited the GnRH-induced MMP activation, invasion, and migration. In addition, we showed that the c-Jun NH(2)-terminal kinase, but not extracellular signal-regulated kinase 1/2 or p38 mitogen-activated protein kinase, signaling pathway was critical for GnRH-mediated up-regulation of MMP, cell invasion, and motility. These results indicate for the first time an expanded role for GnRH in other aspects of ovarian tumor progression, such as metastasis, via activation of MMP and the subsequent increase in cell migration and invasion.

Endocrine signaling in ovarian surface epithelium and cancer

Ovarian cancer is the sixth most common cancer and the fifth leading cause of cancer-related death among women in developed countries. Greater than 85% of human ovarian cancer arises within the ovarian surface epithelium (OSE), with the remainder derived from granulosa cells or, rarely, stroma or germ cells. The pathophysiology of ovarian cancer is the least understood among all major human malignancies because of a poor understanding of the aetiological factors and mechanisms of ovarian cancer progression. There is increasing evidence suggesting that several key reproductive hormones, such as GnRH, gonadotrophins and sex steroids, regulate the growth of normal OSE and ovarian cancer cells. The objective of this review was to highlight the effects of these endocrine factors on ovarian cancer cell growth and to summarize the signalling mechanisms involved in normal human OSE and its neoplastic counterparts.

Cancer biology and hormesis: human tumor cell lines commonly display hormetic (biphasic) dose responses

This article assesses the nature of the dose-response relationship of human tumor cell lines with a wide range of agents including antineoplastics, toxic substances (i.e., environmental pollutants), nonneoplastic drugs, endogenous agonists, and phyto-compounds. Hormetic-like biphasic dose responses were commonly reported and demonstrated in 136 tumor cell lines from over 30 tissue types for over 120 different agents. Quantitative features of these hormetic dose responses were similar, regardless of tumor cell line or agent tested. That is, the magnitude of the responses was generally modest, with maximum stimulatory responses typically not greater than twice the control, while the width of the stimulatory concentration range was usually less than 100-fold. Particular attention was directed to possible molecular mechanisms of the biphasic nature of the dose response, as well as clinical implications in which a low concentration of chemotherapeutic agent may stimulate tumor cell proliferation. Finally, these findings further support the conclusion that hormetic dose responses are broadly generalizable, being independent of biological model, endpoint measured, and stressor agent, and represent a basic feature of biological responsiveness to chemical and physical stressors.

Differential gonadotropin releasing hormone (GnRH) expression, autoregulation and effects in two models of rat luteinized ovarian cells

GnRH has been suggested to participate in corpus luteum function. Here we studied the expression of GnRH mRNA and peptide in two models of rat luteinized tissues: ovarian cells from PMSG-hCG treated prepubertal rats (SPO) and from intrasplenic ovarian tumors (Luteoma). A GnRH autoregulatory effect was evaluated as well as its action on cell proliferation and apoptosis. GnRH mRNA was present in SPO, isolated corpora lutea from SPO and Luteoma from 1 week to 7 months of development. In vitro cultures of Luteoma cells expressed 2-fold higher GnRH mRNA and 10-fold higher GnRH peptide than SPO cells. Buserelin (GnRH analog) increased GnRH mRNA and peptide expression in SPO but not in Luteoma cells. While basal proliferation was very low in Luteoma cells, SPO cells showed a significant increase in cell number by both the thymidine and the MTS methods after 72 h in culture. Buserelin induced a decrease in cell number in both cell types to a similar degree. Although basal apoptosis levels were higher in SPO than in Luteoma cells, Buserelin-induced apoptosis was only detected in Luteoma cells after 48 h treatment. These results show that the two types of rat, luteinized tissues, Luteoma and SPO, markedly differed in some intrinsic properties and in their local GnRH systems. Luteoma cells proliferate very weakly, express and secrete high amounts of GnRH, do not show an autoregulatory effect and respond to the decapeptide with apoptosis stimulation. In contrast SPO cells proliferate significantly, secrete low levels of GnRH but possess a positive, autoregulatory mechanism and respond to GnRH stimulation with impairment of proliferation.

Molecular biology of gonadotropin-releasing hormone (GnRH)-I, GnRH-II, and their receptors in humans

In human beings, two forms of GnRH, termed GnRH-I and GnRH-II, encoded by separate genes have been identified. Although these hormones share comparable cDNA and genomic structures, their tissue distribution and regulation of gene expression are significantly dissimilar. The actions of GnRH are mediated by the GnRH receptor, which belongs to a member of the rhodopsin-like G protein-coupled receptor superfamily. However, to date, only one conventional GnRH receptor subtype (type I GnRH receptor) uniquely lacking a carboxyl-terminal tail has been found in the human body. Studies on the transcriptional regulation of the human GnRH receptor gene have indicated that tissue-specific gene expression is mediated by differential promoter usage in various cell types. Functionally, there is growing evidence showing that both GnRH-I and GnRH-II are potentially important autocrine and/or paracrine regulators in some extrapituitary compartments. Recent cloning of a second GnRH receptor subtype (type II GnRH receptor) in nonhuman primates revealed that it is structurally and functionally distinct from the mammalian type I receptor. However, the human type II receptor gene homolog carries a frameshift and a premature stop codon, suggesting that a full-length type II receptor does not exist in humans.

Gonadotropin-releasing hormone antagonist cetrorelix down-regulates proliferating cell nuclear antigen and epidermal growth factor expression and up-regulates apoptosis in association with enhanced poly(adenosine 5'-diphosphate-ribose) polymerase expression in cultured human leiomyoma cells

The objective of this study was to elucidate the effects of GnRH antagonist Cetrorelix on proliferation and apoptosis in human leiomyoma cells cultured in vitro. Isolated leiomyoma cells were subcultured in phenol red-free DMEM supplemented with 10% fetal bovine serum for 120 h and then stepped down to serum-free conditions in the presence or absence of graded concentrations of Cetrorelix (10(-5) to 10(-8) mol/liter) for 6 d. Cultured leiomyoma cells were used for semiquantitative RT-PCR, immunocytochemistry, Western blot analysis, and terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling assay. RT-PCR analysis revealed the presence of mRNAs encoding for GnRH receptor and epidermal growth factor (EGF) in cultured leiomyoma cells. The number of viable cultured leiomyoma cells was significantly (P < 0.01) decreased by treatment with Cetrorelix compared with untreated control cultures. Immunocytochemical examination demonstrated that treatment with Cetrorelix attenuated the expression of proliferating cell nuclear antigen (PCNA) and EGF in cultured leiomyoma cells. Western blot analysis revealed that treatment with 10(-5) mol/liter Cetrorelix significantly (P < 0.01) decreased PCNA expression. In addition, treatment with 10(-5) mol/liter Cetrorelix remarkably increased the terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling-positive rate and poly(ADP-ribose) polymerase expression at 24 h of treatment compared with untreated control cultures (P < 0.01). Furthermore, treatment with 10(-5) mol/liter Cetrorelix decreased immunoreactive EGF protein and EGF mRNA expression in cultured leiomyoma cells at 4 d of treatment. GnRH antagonist Cetrorelix may directly inhibit leiomyoma cell growth by down-regulating proliferation in association with a decrease in EGF mRNA expression and by up-regulating apoptosis in those cells.

Second-line therapy of advanced ovarian cancer with GnRH analogs

Ovarian cancer is still the first cause of death among female malignancies. The standard treatment adopted in ovarian cancer is a radical surgical treatment or cytoreduction, followed by six courses of platinum-based chemotherapy; second-line regimens are associated with severe side effects. GnRH analogs could represent an alternative therapeutical approach. The aim of our study was to evaluate the role of GnRH analogs in the management of platinum-resistant ovarian cancers. We enrolled 12 patients affected by advanced ovarian cancer, previously treated with six courses of platinum-paclitaxel. In second-line therapy, we used leuprolide on 1, 8, and 28 days of treatment. CA 125 levels were recorded for each patient. One case of clinical partial response was obtained (8.3%). Stable disease was diagnosed in three patients (25%). Progression was recorded in eight cases (66.7%). Progression-free survival was 6 months. The treatment was well tolerated by patients. The high tolerability and the results obtained with leuprolide versus platinum in second-line therapy might permit a better use of the analogs for advanced ovarian cancer.

Pathophysiological Dynamics of Human Ovarian Surface Epithelial Cells in Epithelial Ovarian Carcinogenesis

Epithelial ovarian cancer is responsible for almost half of all the deaths from female genital tract tumors. Major impediments to the clinical treatment of this disease are the relatively asymptomatic progression and a lack of knowledge regarding defined precursor or malignant lesions. Most epithelial ovarian cancers are thought to arise from the transformation of ovarian surface epithelial cells, a single continuous layer of flat-to-cuboidal mesothelial cells surrounding the ovary. To improve our understanding of the pathogenesis of epithelial ovarian cancer, it is necessary to study the biological characteristics of normal ovarian surface epithelial cells. However, this approach has been hampered by the inability to purify and culture such human cells. During the past decade, procedures to isolate and culture human ovarian surface epithelial cells have been developed, and, subsequently, using viral oncogenes, several immortalized cells have been established. This new experimental system is being employed to improve our understanding of the genetic changes leading to the initiation of epithelial ovarian cancer and to identify events in the cancer's development. This review mainly describes the biological dynamics of ovarian surface epithelial cells in the pathogenesis of epithelial ovarian cancer, focusing on humans and excluding small animal models.

Effects of gonadotropin-releasing hormone agonist and dopamine antagonist on hypothalamus-pituitary-gonadal axis of pre-pubertal female red seabream (Pagrus major)

The effects of GnRH agonist (GnRHa) on the hypothalamus-pituitary-gonadal axis were studied in female pre-pubertal red seabream. Sexually immature 16-month-old fish were implanted intramuscularly with cholesterol pellets containing GnRHa or GnRHa in combination with domperidone, putative dopamine antagonist, and reared for 10-20 days. In both GnRHa and GnRHa+domperidone implanted groups, vitellogenesis was observed on Day 10 and ovulation was observed on Day 20, while ovarian development was not observed in the control fish throughout the experimental period. The levels of GnRH receptor mRNA were significantly higher in both GnRHa implanted groups than in the control. The expressions of all three gonadotropin subunit genes were up-regulated and serum luteinizing hormone levels were increased by the GnRHa implantation. Serum testosterone and estradiol-17beta levels were also increased on Day 10 and maintained high levels on Day 20. On the other hand, seabream (sb) GnRH mRNA levels in the brain were relatively low and unchanged in all experiment groups. The present study first shows that GnRH alone can induce precocious puberty in red seabream. These results indicate that the system of pituitary-gonadal axis has already been developed in 16-month-old fish and the commencement of sbGnRH secretion may be an important physiological event for the onset of puberty in the red seabream.

Neutral endopeptidase/CD10 expression in the stroma of epithelial ovarian carcinoma

This study investigated the immunohistochemical expression and localization of neutral endopeptidase (NEP) (CD10), which plays a functional role by degrading bioactive peptides, in ovarian tumors. In normal ovaries and benign cystadenomas, NEP was not detected in any epithelial or stromal cells. In borderline tumors, NEP was detected in the stromal cells in 6 of 7 serous tumors, but not in those from mucinous tumors. In ovarian carcinomas, NEP in the stromal cells was observed in 13 of 20 serous, 8 of 10 endometrioid, and 7 of 10 clear-cell adenocarcinomas. NEP was weakly detected in only 1 of 9 mucinous adenocarcinomas. The staining intensity of stromal NEP was decreased in grades 2 and 3 serous carcinomas compared with that in grade 1 serous carcinomas. In conclusion, NEP was specifically expressed in the stroma of borderline and malignant ovarian tumors, but not in adenomas. Furthermore, stromal NEP was downregulated as the histological grade advanced. These results suggest that NEP may play a role in the regulation of neoplastic transformation and tumor differentiation in epithelial ovarian carcinomas.