Gonadotropin-releasing hormone and ovarian cancer: a functional and mechanistic overview

Whole-Genome Comparative Copy Number Alteration Profiling between Malignant Pleural Mesothelioma and Asbestos-Induced Chronic Pleuritis

Malignant pleural mesothelioma (MPM) is rare and aggressive cancer. The most important risk factor for MPM is exposure to asbestos. In this study, we scanned the genomes of individuals MPM and asbestos-induced chronic pleuritis (AICP) to compare and determine copy number alterations (CNAs) between two asbestos-related diseases. We used high-resolution SNP arrays to compare CNA profiles between MPM (n = 55) and AICP (n = 18). DNAs extracted from pleural tissues in both groups. SNP array analysis revealed common losses at 1p, 3p, 6q, 9p, 13q, 14q, 15q, 16q, 22q and frequent gains at chromosomes 1, 3, 5, 7, 8, and 6p, 12q, 15q, 17p, 20q in MPMs (frequencies max 67%-min 30%; these alterations were not detected in AICPs. Besides detecting well-known MPM-associated CNAs, our high -resolution copy number profiling also detected comparatively rare CNAs for MPMs including losses like 9q33.3, 16q and gains of 1p, 1q, 3p, 3q, 6p, 7q, 15q, 12q, 17p, 20q at significant frequencies in the MPM cohort. We also observed Copy Number gains clustered on the NF2 locus in AICPs, whereas this region was commonly deleted in MPMs. According to this distinct genomic profiles between the two groups, AICPs genomes can be clearly distinguished from highly altered MPM genomes. Hence, we can suggest that SNP arrays can be used as a supporting diagnostic tool in terms of discriminating asbestos-related malignant disease such as MPM and benign pleural lesions, which can be challenging in most instances.

High-grade serous ovarian carcinoma, the "Achiles' hill" for clinicians and molecular biologists: a molecular insight

High-grade serous ovarian carcinoma (HGSOC), the deadliest ovarian cancer, alone accounts for 90% of all its subtypes. Characterized by hallmark mutation of TP53, HGSOC show diverse molecular etiology. HGSOC can arise from both ovarian epithelium as well as the fimbrial epithelium of the fallopian tube. Ovulation induced reactive oxygen species, follicular fluid associated growth factor induced stemness, deregulation of hormone receptors like ER, FSHR, AR and hormones like FSH, LH, prolonged ovulation cycle, use of oral contraceptives are agonists of HGSOC while parity, breastfeeding provide protective effect from HGSOC development. Apart from a generic TP53 mutation, mutation of BRCA1/2, RAD51, BRIP1, PALB2, CHEK2, RAD50 etc., were reportedly associated with development of HGSOC. Epigenetic events like methylation of RASSF1A of RAS signaling pathway,OR51L1, OR51I1, OR51F1 etc. has been reported in HGSOC. Micro-RNAs like miR-1290, miR 27-a-3p miR23a, miR205 were reportedly upregulated in HGSOC. Amongst its cognate subtypes viz. differentiated, immunoreactive, mesenchymal, and proliferative, mesenchymal, and proliferative show worst prognosis. A system biology approach showed five major altered pathways in HGSOC, namely, RB, PI3K/RAS, NOTCH, HRR and FOXM1 signaling. For chemonaive patients, drugs that helps in efflux of reduced glutathione or prevent the redox coupling of GSH-GSSG, like Cisplatin, could be considered as the best therapeutic choice for HGSOC. For patients with BRCA1/2 mutations, PARP inhibitors alone or with Bevacizumab can be effective. Immune checkpoint inhibitors could be effective against immunoreactive subtypes. Identification of genes deregulated in chemoresistance could provide better insights in dealing with the disease.

Identification of N1 methyladenosine-related biomarker predicting overall survival outcomes and experimental verification in ovarian cancer

AIM

This study aimed to construct a N1-methyladenosine (m1A)-related biomarker model for predicting the prognosis of ovarian cancer (OVCA).

METHODS

OVCA samples were clustered into two subtypes using the Non-Negative Matrix Factorization (NMF) algorithm, including TCGA (n = 374) as the training set and GSE26712 (n = 185) as the external validation set. Hub genes, which were screened to construct a risk model, and nomogram to predict the overall survival of OVCA were explored and validated through various bioinformatic analysis and quantitative real-time PCR.

RESULTS

Following bootstrap correction, the C-index of nomogram was 0.62515, showing reliable performance. The functions of DEGs in the high- and low-risk groups were mainly enriched in immune response, immune regulation, and immune-related diseases. The immune cells relevant to the expression of hub genes were explored, for example, Natural Killer (NK) cells, T cells, activated dendritic cells (aDC).

CONCLUSIONS

AADAC, CD38, CACNA1C, and ATP1A3 might be used as m1A-related biomarkers for OVCA, and the nomogram labeled with m1A for the first time had excellent performance for predicting overall survival in OVCA.

NPFF stimulates human ovarian cancer cell invasion by upregulating MMP-9 via ERK1/2 signaling

Neuropeptide FF (NPFF) belongs to the RFamide peptide family. NPFF regulates a variety of physiological functions by binding to a G protein-coupled receptor, NPFFR2. Epithelial ovarian cancer (EOC) is a leading cause of death among gynecological malignancies. The pathogenesis of EOC can be regulated by many local factors, including neuropeptides, through an autocrine/paracrine manner. However, to date, the expression and/or function of NPFF/NPFFR2 in EOC is undetermined. In this study, we show that the upregulation of NPFFR2 mRNA was associated with poor overall survival in EOC. The TaqMan probe-based RT-qPCR showed that NPFF and NPFFR2 were expressed in three human EOC cells, CaOV3, OVCAR3, and SKOV3. In comparison, NPFF and NPFFR2 expression levels were higher in SKOV3 cells than in CaOV3 or OVCAR3 cells. Treatment of SKOV3 cells with NPFF did not affect cell viability and proliferation but stimulated cell invasion. NPFF treatment upregulates matrix metalloproteinase-9 (MMP-9) expression. Using the siRNA-mediated knockdown approach, we showed that the stimulatory effect of NPFF on MMP-9 expression was mediated by the NPFFR2. Our results also showed that ERK1/2 signaling was activated in SKOV3 cells in response to the NPFF treatment. In addition, blocking the activation of ERK1/2 signaling abolished the NPFF-induced MMP-9 expression and cell invasion. This study provides evidence that NPFF stimulates EOC cell invasion by upregulating MMP-9 expression through the NPFFR2-mediated ERK1/2 signaling pathway.

Dissecting the Hormonal Signaling Landscape in Castration-Resistant Prostate Cancer

Understanding the molecular mechanisms underlying prostate cancer (PCa) progression towards its most aggressive, castration-resistant (CRPC) stage is urgently needed to improve the therapeutic options for this almost incurable pathology. Interestingly, CRPC is known to be characterized by a peculiar hormonal landscape. It is now well established that the androgen/androgen receptor (AR) axis is still active in CRPC cells. The persistent activity of this axis in PCa progression has been shown to be related to different mechanisms, such as intratumoral androgen synthesis, AR amplification and mutations, AR mRNA alternative splicing, increased expression/activity of AR-related transcription factors and coregulators. The hypothalamic gonadotropin-releasing hormone (GnRH), by binding to its specific receptors (GnRH-Rs) at the pituitary level, plays a pivotal role in the regulation of the reproductive functions. GnRH and GnRH-R are also expressed in different types of tumors, including PCa. Specifically, it has been demonstrated that, in CRPC cells, the activation of GnRH-Rs is associated with a significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic activity. This antitumor activity is mainly mediated by the GnRH-R-associated Gαi/cAMP signaling pathway. In this review, we dissect the molecular mechanisms underlying the role of the androgen/AR and GnRH/GnRH-R axes in CRPC progression and the possible therapeutic implications.

Gonadotropin-releasing hormone analogs: Mechanisms of action and clinical applications in female reproduction

Extra-hypothalamic GnRH and extra-pituitary GnRH receptors exist in multiple human reproductive tissues, including the ovary, endometrium and myometrium. Recently, new analogs (agonists and antagonists) and modes of GnRH have been developed for clinical application during controlled ovarian hyperstimulation for assisted reproductive technology (ART). Additionally, the analogs and upstream regulators of GnRH suppress gonadotropin secretion and regulate the functions of the reproductive axis. GnRH signaling is primarily involved in the direct control of female reproduction. The cellular mechanisms and action of the GnRH/GnRH receptor system have been clinically applied for the treatment of reproductive disorders and have widely been introduced in ART. New GnRH analogs, such as long-acting GnRH analogs and oral nonpeptide GnRH antagonists, are being continuously developed for clinical application. The identification of the upstream regulators of GnRH, such as kisspeptin and neurokinin B, provides promising potential to develop these upstream regulator-related analogs to control the hypothalamus-pituitary-ovarian axis.

Gonadotropin-Releasing Hormone Receptors in Prostate Cancer: Molecular Aspects and Biological Functions

Pituitary Gonadotropin-Releasing Hormone receptors (GnRH-R) mediate the activity of the hypothalamic decapeptide GnRH, thus playing a key role in the regulation of the reproductive axis. Early-stage prostate cancer (PCa) is dependent on serum androgen levels, and androgen-deprivation therapy (ADT), based on GnRH agonists and antagonists, represents the standard therapeutic approach for PCa patients. Unfortunately, the tumor often progresses towards the more aggressive castration-resistant prostate cancer (CRPC) stage. GnRH receptors are also expressed in CRPC tissues, where their binding to both GnRH agonists and antagonists is associated with significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic effects, mediated by the Gαi/cAMP signaling cascade. GnRH agonists and antagonists are now considered as an effective therapeutic strategy for CRPC patients with many clinical trials demonstrating that the combined use of these drugs with standard therapies (i.e., docetaxel, enzalutamide, abiraterone) significantly improves disease-free survival. In this context, GnRH-based bioconjugates (cytotoxic drugs covalently linked to a GnRH-based decapeptide) have been recently developed. The rationale of this treatment is that the GnRH peptide selectively binds to its receptors, delivering the cytotoxic drug to CRPC cells while sparing nontumor cells. Some of these compounds have already entered clinical trials.

Apoptotic Effects of Drug Targeting Conjugates Containing Different GnRH Analogs on Colon Carcinoma Cells

The wide range of cellular target reactions (e.g., antitumor) of gonadotropin-releasing hormone (GnRH) variants provides the possibility to develop multifunctional GnRH conjugates. The aim of our work was to compare the cytotoxic/apoptotic activity of different GnRH-based, daunorubicin (Dau)-linked conjugates with or without butyrated Lys in position 4 (⁴Lys(Bu)) at a molecular level in a human colorectal carcinoma cell line. Cell viability was measured by impedimetry, cellular uptake and apoptosis were studied by flow cytometry, and the expression of apoptosis-related genes was analyzed by qRT-PCR. The modification with ⁴Lys(Bu) resulted in an increased cytotoxic and apoptotic effects and cellular uptake of the GnRH-I and GnRH-III conjugates. Depending on the GnRH isoform and the presence of ⁴Lys(Bu), the conjugates could regulate the expression of several apoptosis-related genes, especially tumor necrosis factor (TNF), tumor protein p53 (TP53) and the members of growth-factor signaling. The stronger cytotoxicity of GnRH-I and GnRH-III conjugates containing ⁴Lys(Bu) was associated with a stronger inhibitory effect on the expression of growth-factor signaling elements in comparison with their ⁴Ser counterparts, in which the upregulation of TP53 and caspases (e.g., CASP9) seemed to play a more important role. We were able to provide further evidence that targeting the GnRH receptor could serve as a successful therapeutic approach in colon cancer, and GnRH-III-[⁴Lys(Bu),⁸Lys(Dau=Aoa)] proved to be the best candidate for this purpose.

Risk of ovarian cancer in women treated with ovarian stimulating drugs for infertility

BACKGROUND

This is an updated version of the original Cochrane Review published in the Cochrane Library in 2013 (Issue 8) on the risk of ovarian cancer in women using infertility drugs when compared to the general population or to infertile women not treated. The link between fertility drugs and ovarian cancer remains controversial.

OBJECTIVES

To evaluate the risk of invasive ovarian cancer and borderline ovarian tumours in women treated with ovarian stimulating drugs for subfertility.

SEARCH METHODS

The original review included published and unpublished observational studies from 1990 to February 2013. For this update, we extended the searches from February 2013 to November 2018; we evaluated the quality of the included studies and judged the certainty of evidence by using the GRADE approach. We have reported the results in a Summary of findings table to present effect sizes across all outcome types.

SELECTION CRITERIA

In the original review and in this update, we searched for randomised controlled trials (RCTs) and non-randomised studies and case series including more than 30 participants.

DATA COLLECTION AND ANALYSIS

At least two review authors independently conducted eligibility and 'Risk of bias' assessments and extracted data. We grouped studies based on the fertility drug used for two outcomes: borderline ovarian tumours and invasive ovarian cancer. We conducted no meta-analyses due to expected methodological and clinical heterogeneity.

MAIN RESULTS

We included 13 case-control and 24 cohort studies (an additional nine new cohort and two case-control studies), which included a total of 4,684,724 women.Two cohort studies reported an increased incidence of invasive ovarian cancer in exposed subfertile women compared with unexposed women. One reported a standardised incidence ratio (SIR) of 1.19 (95% confidence interval (CI) 0.54 to 2.25) based on 17 cancer cases. The other cohort study reported a hazard ratio (HR) of 1.93 (95% CI 1.18 to 3.18), and this risk was increased in women remaining nulligravid after using clomiphene citrate (HR 2.49, 95% CI 1.30 to 4.78) versus multiparous women (HR 1.52, 95% CI 0.67 to 3.42) (very low-certainty evidence). The slight increase in ovarian cancer risk among women having between one and three cycles of in vitro fertilisation (IVF) was reported, but this was not clinically significant (P = 0.18). There was no increase in risk of invasive ovarian cancer after use of infertility drugs in women with the BRCA mutation according to one cohort and one case-control study. The certainty of evidence as assessed using GRADE was very low.For borderline ovarian tumours, one cohort study reported increased risk in exposed women with an SIR of 3.61 (95% CI 1.45 to 7.44), and this risk was greater after treatment with clomiphene citrate (SIR 7.47, 95% CI 1.54 to 21.83) based on 12 cases. In another cohort study, the risk of a borderline ovarian tumour was increased, with an HR of 4.23 (95% CI 1.25 to 14.33), for subfertile women treated with IVF compared with a non-IVF-treated group with more than one year of follow-up. A large cohort reported increased risk of borderline ovarian tumours, with HR of 2.46 (95% CI 1.20 to 5.04), and this was based on 17 cases. A significant increase in serous borderline ovarian tumours was reported in one cohort study after the use of progesterone for more than four cycles (risk ratio (RR) 2.63, 95% CI 1.04 to 6.64). A case-control study reported increased risk after clomiphene citrate was taken, with an SIR of 2.5 (95% CI 1.3 to 4.5) based on 11 cases, and another reported an increase especially after human menopausal gonadotrophin was taken (odds ratio (OR) 9.38, 95% CI 1.66 to 52.08). Another study estimated an increased risk of borderline ovarian tumour, but this estimation was based on four cases with no control reporting use of fertility drugs. The certainty of evidence as assessed using GRADE was very low.However, although some studies suggested a slight increase in risks of ovarian cancer and borderline ovarian tumour, none provided moderate- or high-certainty evidence, as summarised in the GRADE tables.

AUTHORS' CONCLUSIONS

Since the last version of this review, only a few new relevant studies have provided additional findings with supporting evidence to suggest that infertility drugs may increase the risk of ovarian cancer slightly in subfertile women treated with infertility drugs when compared to the general population or to subfertile women not treated. The risk is slightly higher in nulliparous than in multiparous women treated with infertility drugs, and for borderline ovarian tumours. However, few studies have been conducted, the number of cancers is very small, and information on the dose or type of fertility drugs used is insufficient.

The Anti-proliferative Activity of GnRH Through Downregulation of the Akt/ERK Pathways in Pancreatic Cancer

Gonadotropin-releasing hormone (GnRH) has been demonstrated to exert anti-proliferative functions on various tumor cells in endometrial, ovarian, bladder, or prostate cancer as a part of the autocrine system. In addition, the expression levels of GnRH and its receptor had been identified in breast cancer or non-reproductive cancers, such as glioblastoma and pancreatic cancer. Previous studies have reported abnormal GnRH expression in several malignant tumors, suggesting that GnRH and its receptor might be essential for tumourigenesis. In the present study, we attempted to clarify the mechanisms underlying GnRH function in cell proliferation in pancreatic cancer. Our results indicated that GnRH expression might be essential for the malignancy of pancreatic cancer. We then found that GnRH overexpression can induce cell apoptosis through activating the Bcl-2/Bax pathway and autophagy might be involved in the GnRH-mediated apoptosis in Panc1 cells. Further investigation showed that the inhibition of GnRH may promote tumor invasion and migration through upregulation of MMP2 expression in pancreatic cancer cells. Moreover, our results indicated that GnRH can regulate the Akt/ERK1/2 pathways to promote cell proliferation by inhibiting cell apoptosis in Panc1 cells. Therefore, our finding exhibited that the regulation of GnRH expression may be essential for tumourigenesis in pancreatic cancer, and might be a potential target for the treatment of the patients with pancreatic cancer.

Comparative aspects of GnRH-Stimulated signal transduction in the vertebrate pituitary - Contributions from teleost model systems

Gonadotropin-releasing hormone (GnRH) is a major regulator of reproduction through actions on pituitary gonadotropin release and synthesis. Although it is often thought that pituitary cells are exposed to only one GnRH, multiple GnRH forms are delivered to the pituitary of teleost fishes; interestingly this can include the cGnRH-II form usually thought to be non-hypophysiotropic. GnRHs can regulate other pituitary cell-types, both directly as well as indirectly, and multiple GnRH receptors (GnRHRs) may also be expressed in the pituitary, and even within a single pituitary cell-type. Literature on the differential actions of native GnRH isoforms in primary pituitary cells is largely derived from teleost fishes. This review will outline the diversity and complexity of GnRH-GnRHR signal transduction found within vertebrate gonadotropes as well as extra-gonadotropic sites with special emphasis on comparative studies from fish models. The implications that GnRHR transduction mechanisms are GnRH isoform-, function-, and cell-specific are also discussed.

Differential roles of PKC isoforms (PKCs) in GnRH stimulation of MAPK phosphorylation in gonadotrope derived cells

The role of protein kinase C (PKC) isoforms (PKCs) in GnRH-stimulated MAPK [ERK1/2, JNK1/2 and p38) phosphorylation was examined in gonadotrope derived cells. GnRH induced a protracted activation of ERK1/2 and a slower and more transient activation of JNK1/2 and p38MAPK. Gonadotropes express conventional PKCα and PKCβII, novel PKCδ, PKCε and PKCθ, and atypical PKC-ι/λ. The use of green fluorescent protein (GFP)-PKCs constructs revealed that GnRH induced rapid translocation of PKCα and PKCβII to the plasma membrane, followed by their redistribution to the cytosol. PKCδ and PKCε localized to the cytoplasm and Golgi, followed by the rapid redistribution by GnRH of PKCδ to the perinuclear zone and of PKCε to the plasma membrane. The use of dominant negatives for PKCs and peptide inhibitors for the receptors for activated C kinase (RACKs) has revealed differential role for PKCα, PKCβII, PKCδ and PKCε in ERK1/2, JNK1/2 and p38MAPK phosphorylation in a ligand-and cell context-dependent manner. The paradoxical findings that PKCs activated by GnRH and PMA play a differential role in MAPKs phosphorylation may be explained by persistent vs. transient redistribution of selected PKCs or redistribution of a given PKC to the perinuclear zone vs. the plasma membrane. Thus, we have identified the PKCs involved in GnRH stimulated MAPKs phosphorylation in gonadotrope derived cells. Once activated, the MAPKs will mediate the transcription of the gonadotropin subunits and GnRH receptor genes.

GnRH in the Human Female Reproductive Axis

Gonadotropin-releasing hormone (GnRH) is recognized as the central regulator of the functions of the pituitary-gonadal axis. The increasing knowledge on the mechanisms controlling the development and the function of GnRH-producing neurons is leading to a better diagnostic and therapeutic approach for hypogonadotropic hypogonadisms and for alterations of the puberty onset. During female life span, the function of the GnRH pulse generator may be affected by a number of inputs from other neuronal systems, offering alternative strategies for diagnostic and therapeutic interventions. Moreover, the identification of a GnRH/GnRH receptor system in both human ovary and endometrium has widened the spectrum of action of the peptide outside its hypothalamic functions. The pharmacological use of GnRH itself or its synthetic analogs (agonists and antagonists) provides a valid tool to either stimulate or block gonadotropin secretion and to modulate the female fertility in several reproductive disorders and in assisted reproduction technology. The use of GnRH agonists in young female patients undergoing chemotherapy is also considered a promising therapeutic approach to counteract iatrogenic ovarian failure.

Goserelin promotes the apoptosis of epithelial ovarian cancer cells by upregulating forkhead box O1 through the PI3K/AKT signaling pathway

Gonadotropins, including luteinizing hormone (LH) and follicle stimulating hormone (FSH), are conducive to the growth of ovarian cancer based on the ‘gonadotropin theory’ and are regulated by gonadotropin-releasing hormone (GnRH). The present study was carried out to investigate the effect of goserelin, a GnRH agonist, on the apoptosis of epithelial ovarian cancer (EOC) cells and the underlying in vitro and in vivo mechanisms. Through flow cytometry, Hoechst staining and TUNEL staining, we demonstrated that goserelin promoted the apoptosis of EOC cells both in vitro and in vivo. Through human apoptosis gene PCR array, we verified that the promotion of EOC cell apoptosis by goserelin was linked to the upregulation of members of the tumor necrosis factor (TNF) and TNF receptor superfamilies, which have been identified as downstream targets of forkhead box O1 (FOXO1). Goserelin enhanced FOXO1 expression, and siRNA-mediated knockdown of FOXO1 abrogated the induction of apoptosis by goserelin. Moreover, goserelin decreased AKT activity, and FOXO1 upregulation by goserelin was dependent on the phosphatidylinositol 3-kinase (PI3K)/AKT pathway. In vivo, the expression of key factors in the PI3K/AKT/FOXO1 pathway was consistent with that observed in vitro. In conclusion, our data suggested that goserelin may promote EOC cell apoptosis by upregulating FOXO1 through the PI3K/AKT signaling pathway. We believe that GnRH agonists may be potential antitumor agents, and key factors in the PI3K/AKT-FOXO1 pathway may also be novel therapeutic targets for the treatment of EOC.

Differential roles of PKC isoforms (PKCs) and Ca2+ in GnRH and phorbol 12-myristate 13-acetate (PMA) stimulation of p38MAPK phosphorylation in immortalized gonadotrope cells

We examined the role of PKCs and Ca²⁺ in GnRH-stimulated p38MAPK phosphorylation in the gonadotrope derived αT3-1 and LβT2 cell lines. GnRH induced a slow and rapid increase in p38MAPK phosphorylation in αT3-1 and LβT2 cells respectively, while PMA gave a slow response. The use of dominant negatives for PKCs and peptide inhibitors for the receptors for activated C kinase (RACKs), has revealed differential role for PKCα, PKCβII, PKCδ and PKCε in p38MAPK phosphorylation in a ligand-and cell context-dependent manner. The paradoxical findings that PKCs activated by GnRH and PMA play a differential role in p38MAPK phosphorylation may be explained by differential localization of the PKCs. Basal, GnRH- and PMA- stimulation of p38MAPK phosphorylation in αT3-1 cells is mediated by Ca²⁺ influx via voltage-gated Ca²⁺ channels and Ca²⁺ mobilization, while in the differentiated LβT2 gonadotrope cells it is mediated only by Ca²⁺ mobilization. p38MAPK resides in the cell membrane and is relocated to the nucleus by GnRH (∼5 min). Thus, we have identified the PKCs and the Ca²⁺ pools involved in GnRH stimulated p38MAPK phosphorylation.

The gonadotropin-releasing hormone system: Perspectives from reproduction to cancer (Review)

Recently, an increasing amount of evidence indicates that human gonadotropin-releasing hormone (hGnRH) and its receptor (hGnRHR) are important regulatory components not only to the reproduction process but also in the regulation of some cancer cell functions such as cell proliferation, in both hormone-dependent and -independent types of tumors. The hGnRHR is a naturally misfolded protein that is retained mostly in the endoplasmic reticulum; however, this mechanism can be overcome by treatment with several pharmacoperones, therefore, increasing the amount of receptors in the cell membrane. In addition, several reports indicate that the expression level of hGnRHR in tumor cells is even lower than in pituitary or gonadotrope cells. The signal transduction pathways activated by hGnRH in both gonadotrope and different cancer cell types are described in the present review. We also discuss how the rescue of misfolded receptors in tumor cells could be a promising strategy for cancer therapy.

GnRH and GnRH receptors in the pathophysiology of the human female reproductive system

BACKGROUND

Human reproduction depends on an intact hypothalamic-pituitary-gonadal (HPG) axis. Hypothalamic gonadotrophin-releasing hormone (GnRH) has been recognized, since its identification in 1971, as the central regulator of the production and release of the pituitary gonadotrophins that, in turn, regulate the gonadal functions and the production of sex steroids. The characteristic peculiar development, distribution and episodic activity of GnRH-producing neurons have solicited an interdisciplinary interest on the etiopathogenesis of several reproductive diseases. The more recent identification of a GnRH/GnRH receptor (GnRHR) system in both the human endometrium and ovary has widened the spectrum of action of the peptide and of its analogues beyond its hypothalamic function.

METHODS

An analysis of research and review articles published in international journals until June 2015 has been carried out to comprehensively summarize both the well established and the most recent knowledge on the physiopathology of the GnRH system in the central and peripheral control of female reproductive functions and diseases.

RESULTS

This review focuses on the role of GnRH neurons in the control of the reproductive axis. New knowledge is accumulating on the genetic programme that drives GnRH neuron development to ameliorate the diagnosis and treatment of GnRH deficiency and consequent delayed or absent puberty. Moreover, a better understanding of the mechanisms controlling the episodic release of GnRH during the onset of puberty and the ovulatory cycle has enabled the pharmacological use of GnRH itself or its synthetic analogues (agonists and antagonists) to either stimulate or to block the gonadotrophin secretion and modulate the functions of the reproductive axis in several reproductive diseases and in assisted reproduction technology. Several inputs from other neuronal populations, as well as metabolic, somatic and age-related signals, may greatly affect the functions of the GnRH pulse generator during the female lifespan; their modulation may offer new possible strategies for diagnostic and therapeutic interventions. A GnRH/GnRHR system is also expressed in female reproductive tissues (e.g. endometrium and ovary), both in normal and pathological conditions. The expression of this system in the human endometrium and ovary supports its physiological regulatory role in the processes of trophoblast invasion of the maternal endometrium and embryo implantation as well as of follicular development and corpus luteum functions. The GnRH/GnRHR system that is expressed in diseased tissues of the female reproductive tract (both benign and malignant) is at present considered an effective molecular target for the development of novel therapeutic approaches for these pathologies. GnRH agonists are also considered as a promising therapeutic approach to counteract ovarian failure in young female patients undergoing chemotherapy.

CONCLUSIONS

Increasing knowledge about the regulation of GnRH pulsatile release, as well as the therapeutic use of its analogues, offers interesting new perspectives in the diagnosis, treatment and outcome of female reproductive disorders, including tumoral and iatrogenic diseases.

GnRH participates in the self-renewal of A549-derived lung cancer stem-like cells through upregulation of the JNK signaling pathway

Lung cancer is the leading cause of cancer-related mortality in humans. Exploration of the mechanisms underlying the self-renewal and stemness maintenance of cancer stem-like cells (CSLCs) will open new avenues in lung cancer diagnosis and therapy. Here, we isolated and identified a subpopulation of lung cancer stem-like cells (LCSLCs) from non-small cell lung carcinoma (NSCLC) A549 cells with features including self-renewal capacity in vitro, elevated tumorigenic activity in vivo, and high expression of stemness markers CD44, CD133, aldehyde dehydrogenase 1 (ALDH1) and Sox2, using a serum-free suspension sphere-forming culture method. We then found a higher expression level of gonadotropin-releasing hormone (GnRH) in the LCSLCs using a microarray assay, suggesting that GnRH may play a role in the self-renewal capacity and stemness maintenance in lung cancer cells. In addition, the suppression of GnRH capacity negatively regulated self-renewal and stemness maintenance in the LCSLCs. Overexpression of GnRH promoted stemness properties of A549-derived LCSLCs, indicating that GnRH expression is essential for the self-renewal and stemness maintenance in LCSLCs. Moreover, further investigations demonstrated that the promotion of GnRH functions of self-renewal and stemness maintenance in LCSLCs was associated with the JNK signaling pathway. Therefore, our results showed that GnRH participates in the self-renewal capacity and stemness maintenance of LCSLCs by upregulating the JNK signaling pathway, and GnRH may be useful as an alternative LCSLC therapy.

Effect of gonadotropin-releasing hormone agonist on ES-2 ovarian cancer cells

OBJECTIVE

Gonadotropin-releasing hormone (GnRH) receptor is found in the ovarian tissue, including epithelial ovarian cancer (EOC), suggesting that GnRH agonists may have direct action on EOC.

MATERIALS AND METHODS

Ovarian clear cell cancer (ES-2) cells were treated with low-dose GnRH agonist with/without low-dose paclitaxel (1 μM D-Lys(6) with/without 0.5 μM or 1.0 μM paclitaxel). Growth and behavior of ES-2 cells were evaluated.

RESULTS

Use of either D-Lys(6) or paclitaxel or a combination of the two did not affect the morphology and growth pattern of ES-2 cells. However, ability of migration and invasion of ES-2 cells was significantly decreased in either use of D-Lys(6) or paclitaxel and more apparent with the combination. Type I GnRH receptor expression of ES-2 was not altered significantly by the combination.

CONCLUSION

GnRH agonist might modify the ES-2 ovarian cancer cells, and its role might be independent, additional or synergistic, suggesting the potential role of the use of GnRH agonist in the management of clear cell type of the ovarian cancer. However, the results of this study were derived using ES-2 ovarian cancer cells, and might not be valid in other cell types of ovarian cancers.

Intra-testicular signals regulate germ cell progression and production of qualitatively mature spermatozoa in vertebrates

Spermatogenesis, a highly conserved process in vertebrates, is mainly under the hypothalamic-pituitary control, being regulated by the secretion of pituitary gonadotropins, follicle stimulating hormone, and luteinizing hormone, in response to stimulation exerted by gonadotropin releasing hormone from hypothalamic neurons. At testicular level, gonadotropins bind specific receptors located on the somatic cells regulating the production of steroids and factors necessary to ensure a correct spermatogenesis. Indeed, besides the endocrine route, a complex network of cell-to-cell communications regulates germ cell progression, and a combination of endocrine and intra-gonadal signals sustains the production of high quality mature spermatozoa. In this review, we focus on the recent advances in the area of the intra-gonadal signals supporting sperm development.

Gonadotropin-releasing hormone-regulated prohibitin mediates apoptosis of the gonadotrope cells

GnRH regulates circulating levels of the gonadotropins but has also been implicated in establishing the gonadotrope cell population. Consistent with this, GnRH induces proliferation of partially differentiated gonadotropes, while reducing the numbers of fully differentiated cells. We have previously reported that the proapoptotic protein, prohibitin (PHB) is expressed more abundantly in gonadotrope-derived LβT2 cells than in partially differentiated αT3-1 gonadotrope precursor cells, suggesting a possible role for PHB in GnRH-induced apoptosis. We show here that PHB is required for GnRH-induced apoptosis in mature gonadotropes. PHB expression and activity are regulated by GnRH: its transcription is via c-Jun NH2-terminal kinase, whereas its nuclear export follows activation of ERK. Moreover, PHB levels are down-regulated by microRNA27, which is expressed at lower levels in mature gonadotropes, possibly explaining the switch to an apoptotic response with development. PHB is required for mitochondrial import of the proapoptotic BAX, whose expression is also induced by GnRH-activated c-Jun NH2-terminal kinase, as is expression of the BH3-only protein, HRK, and this too plays a role in GnRH-induced apoptosis. Finally, we show that gonadotrope-specific PHB-knockout mice display reproductive abnormalities, including a larger gonadotrope population, increased LH levels, reduced fertility, and altered gonad development. We thus demonstrate a role for PHB in GnRH-induced cell death in mature gonadotropes, which is crucial for the normal development and function of the reproductive axis.

Risk of ovarian cancer in women treated with ovarian stimulating drugs for infertility

BACKGROUND

The use of assisted reproductive techniques is increasing, but the possible link between fertility drugs and ovarian cancer remains controversial.

OBJECTIVES

To evaluate the risk of ovarian cancer in women treated with ovulation stimulating drugs for subfertility.

SEARCH METHODS

We searched for published and unpublished observational studies from 1990 to February 2013. The following databases were used: the Cochrane Gynaecological Cancer Collaborative Review Group's Trial Register, Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 1, MEDLINE (to February week 4 2013), EMBASE (to 2013 week 09) and databases of conference abstracts. We also scanned reference lists of retrieved articles. The search was not restricted by language of publication.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs) and non-randomised studies, and case series including more than 30 participants, reporting on women with exposure to ovarian stimulating drugs for treatment of subfertility and histologically confirmed borderline or invasive ovarian cancer.

DATA COLLECTION AND ANALYSIS

At least two review authors independently conducted eligibility and 'Risk of bias' assessment, and extracted data. We grouped studies based on the fertility drug used for two outcomes: borderline ovarian tumours and invasive ovarian cancer. We expressed findings as adjusted odds ratio (OR), risk ratio (RR), hazard ratio (HR) or crude OR if adjusted values were not reported and standardised incidence ratio (SIR) where reported. We conducted no meta-analyses due to expected methodological and clinical heterogeneity.

MAIN RESULTS

We included 11 case-control studies and 14 cohort studies, which included a total of 182,972 women.Seven cohort studies showed no evidence of an increased risk of invasive ovarian cancer in subfertile women treated with any drug compared with untreated subfertile women. Seven case-control studies showed no evidence of an increased risk, compared with control women of a similar age. Two cohort studies reported an increased incidence of invasive ovarian cancer in subfertile women treated with any fertility drug compared with the general population. One of these reported a SIR of 5.0 (95% confidence interval (CI) 1.0 to 15), based on three cancer cases, and a decreased risk when cancer cases diagnosed within one year of treatment were excluded from the analysis(SIR 1.67, 95% CI 0.02 to 9.27). The other cohort study reported an OR of 2.09 (95% CI 1.39 to 3.12), based on 26 cases.For borderline ovarian tumours, exposure to any fertility drug was associated with a two to three-fold increased risk in two case-control studies. One case-control study reported an OR of 28 (95% CI 1.5 to 516), which was based on only four cases. In one cohort study, there was more than a two-fold increase in the incidence of borderline tumours compared with the general population (SIR 2.6, 95% CI 1.4 to 4.6) and in another the risk of a borderline ovarian tumour was HR 4.23 (95% CI 1.25 to 14.33) for subfertile women treated with in vitro fertilisation (IVF) compared with a non-IVF treated group with more than one year of follow-up.There was no evidence of an increased risk in women exposed to clomiphene alone or clomiphene plus gonadotrophin, compared with unexposed women. One case-control study reported an increased risk in users of human menopausal gonadotrophin (HMG)(OR 9.4, 95% CI 1.7 to 52). However, this estimate is based on only six cases with a history of HMG use.

AUTHORS' CONCLUSIONS

We found no convincing evidence of an increase in the risk of invasive ovarian tumours with fertility drug treatment. There may be an increased risk of borderline ovarian tumours in subfertile women treated with IVF. Studies showing an increase in the risk of ovarian cancer had a high overall risk of bias, due to retrospective study design, lack of accounting for potential confounding and estimates based on a small number of cases. More studies at low risk of bias are needed.

Current and future applications of GnRH, kisspeptin and neurokinin B analogues

Reproductive hormones affect all stages of life from gamete production, fertilization, fetal development and parturition, neonatal development and puberty through to adulthood and senescence. The reproductive hormone cascade has, therefore, been the target for the development of numerous drugs that modulate its activity at many levels. As the central regulator of the cascade, gonadotropin-releasing hormone (GnRH) agonists and antagonists have found extensive applications in treating a wide range of hormone-dependent diseases, such as precocious puberty, prostate cancer, benign prostatic hyperplasia, endometriosis and uterine fibroids, as well as being an essential component of in vitro fertilization protocols. The neuroendocrine peptides that regulate GnRH neurons, kisspeptin and neurokinin B, have also been identified as therapeutic targets, and novel agonists and antagonists are being developed as modulators of the cascade upstream of GnRH. Here, we review the development and applications of analogues of the major neuroendocrine peptide regulators of the reproductive hormone cascade: GnRH, kisspeptin and neurokinin B.

Ovarian epithelial tumors and reproductive factors: a systematic review

PURPOSE

The aim of this systematic review is to summarize the current knowledge about the etiology and pathogenesis of borderline tumors ovarian cancer with special emphasis on the role of endocrine treatments and reproductive factors to establish a foundation for future studies.

METHODS

We performed a systematic review on the relation between ovarian epithelial tumors (OET) and reproductive factors using the keywords: ovarian cancer, ovarian tumor, ovarian borderline tumor, age at menarche, age at menopause, parity, infertility, PCO syndrome, oral contraception, menopausal hormone therapy, fertility treatment. Totally, 3,290 abstracts were scanned for their relevance in this publication and 127 were finally included.

RESULTS

The incidence of ovarian epithelial cancer and ovarian borderline tumors is influenced by certain reproductive factors. The strongest protective effects are conferred by parity and use of oral contraceptive pills. Recent molecular biologic and histopathologic studies prove that OET represent a diverse group of tumors, each histologic type with a different genetic background. This is at least partly reflected in epidemiologic and clinical studies showing different risk modulating effects of reproductive factors and endocrine therapies on OET.

CONCLUSIONS

The etiology and pathogenesis of ovarian cancer are still not fully understood. None of the so far proposed hypothesis on the development of OET can fully account for the epidemiologic and clinical findings in the context of reproductive factors and OET development. Further research approaches are warranted and need to put more weight on the clinical and genetical diversity of OET to yield a more detailed insight into their pathogenesis.

GnRH-(1-5) transactivates EGFR in Ishikawa human endometrial cells via an orphan G protein-coupled receptor

The decapeptide GnRH is known for its central role in the regulation of the hypothalamo-pituitary-gonadal axis. In addition, it is also known to have local effects within peripheral tissues. The zinc metalloendopeptidase, EC 3.4.24.15 (EP24.15), can cleave GnRH at the Tyr(5)-Gly(6) bond to form the pentapeptide, GnRH-(1-5). The central and peripheral effect of GnRH-(1-5) is different from its parent peptide, GnRH. In the current study, we examined the effect of GnRH-(1-5) on epidermal growth factor receptor (EGFR) phosphorylation and cellular migration. Using the Ishikawa cell line as a model of endometrial cancer, we demonstrate that GnRH-(1-5) stimulates epidermal growth factor release, increases the phosphorylation of EGFR (P < .05) at three tyrosine sites (992, 1045, 1068), and promotes cellular migration. In addition, we also demonstrate that these actions of GnRH-(1-5) are mediated by the orphan G protein-coupled receptor 101 (GPR101). Down-regulation of GPR101 expression blocked the GnRH-(1-5)-mediated release of epidermal growth factor and the subsequent phosphorylation of EGFR and cellular migration. These results suggest that GPR101 is a critical requirement for GnRH-(1-5) transactivation of EGFR in Ishikawa cells.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

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.

CA215 and GnRH receptor as targets for cancer therapy

Two monoclonal antibodies (Mabs), RP215 and GHR106, were selected for the preclinical evaluations of anti-cancer drugs targeting various human cancers including those of the ovary, cervix, lung, and liver. Both Mabs were shown to react with pan cancer markers, which are over-expressed on the surface of almost all human cancers. RP215 Mab was shown to react with the carbohydrate-associated epitope(s) of cancer cell-expressed glycoproteins, mainly consisting of immunoglobulin superfamily (IgSF) proteins and mucins, generally known as CA215. GHR106 Mab was generated against the extracellular domain of human GnRH receptor, which is also highly expressed on the cancer cell surface. Preclinical studies were performed to evaluate the efficacy of these two Mabs as anti-cancer drugs for treating human cancers. High tumor specificity of RP215 Mab was demonstrated with immunohistochemical staining studies of various cancer cell lines, as well as normal and cancerous tissue sections. These two Mabs were shown to induce apoptosis as well as complement-dependent cytotoxicity upon treatment to many cultured cancer cells. Significant dose-dependent growth inhibition of tumor cells from several different tissue origins were demonstrated by nude mouse experiments. It was further demonstrated that GHR106 Mab can function as long-acting GnRH analogs in its biological actions. Efforts were made to generate human/mouse chimeric forms of the GHR106 Mab. Based on the results of these preclinical studies, we believe that these two Mabs, in chimeric or humanized forms, can be developed into suitable therapeutic agents for treatment of human cancers as anti-cancer drugs.

The extrapituitary effects of GnRH antagonists and their potential clinical implications: a narrated review

Potential roles of gonadotropin-releasing hormone (GnRH) antagonists on GnRH/GnRH receptor systems and their effects on the extrapituitary tissues are largely elusive. In this narrated review, we summarized the systemic effects of GnRH antagonists on ovary, endometrium, embryo implantation, placental development, fetal teratogenicity, reproductive tissue cancer cells, and heart while briefly reviewing the GnRH and GnRH receptor system. GnRH antagonists may have direct effects on ovarian granulosa cells. Data are conflicting regarding their effects on endometrial receptivity. The GnRH antagonists may potentially have detrimental effect on early placentation by decreasing the invasive ability of cytotrophoblasts if the exposure to them occurs during early pregnancy. The GnRH antagonists were not found to increase the rates of congenital malformations. Comparative clinical data are required to explore their systemic effects on various extrapituitary tissues such as on cardiac function in the long term as well as their potential use in other human cancers that express GnRH receptors.

Gonadotropin signalling in epithelial ovarian cancer

Ovarian cancer is the most lethal of all gynecologic malignancies, although its aetiology remains poorly understood. A role for the gonadotropins, follicle-stimulating hormone (FSH) and luteinising hormone (LH), has been implicated in a variety of different aspects of ovarian cancer tumorigenesis, including cellular proliferation, migration and invasion. This review focuses on the latest advances in knowledge concerning signalling pathways and functional consequences of gonadotropin action, including changes in protein-, miRNA- and gene expression, in epithelial ovarian cancer cells.

Gonadotropin-releasing hormone-II increases membrane type I metalloproteinase production via beta-catenin signaling in ovarian cancer cells

GnRH-II is produced by ovarian cancer cells and enhances their invasiveness in vitro. In our studies of OVCAR-3 and CaOV-3 ovarian cancer cell lines, GnRH-II treatment induced phosphorylation of Akt and glycogen synthase kinase (GSK)3β, as well as β-catenin accumulation in the nucleus, and the latter was reduced by small interfering RNA (siRNA)-mediated depletion of the GnRH receptor. The phosphatidylinositol 3 kinase (PI3K)/Akt pathway is involved in β-catenin-dependent signaling, and pretreatment of these human ovarian cancer cells with a PI3K/Akt inhibitor, LY294002, attenuated GnRH-II-stimulated phosphorylation of GSK3β and inhibited GnRH-II-induced invasion. It also attenuated GnRH-II induced trans-activation of a β-catenin-dependent reporter gene, most likely because GSK3β phosphorylation promotes translocation of β-catenin to the nucleus. Membrane type I matrix metalloproteinase (MT1-MMP) contributes to tumor progression directly, or by processing the latent MMP-2 zymogen, and is a known target of β-catenin signaling. When OVCAR-3 and CaOV-3 cells were treated with GnRH-II, MT1-MMP levels increased approximately 3-fold, whereas siRNA-mediated depletion of GnRH receptor or pretreatment with LY294002 abrogated this. In addition, lithium chloride, which increases GSK3β phosphorylation and the nuclear translocation of β-catenin, increased MT1-MMP levels in these ovarian cancer cells. By contrast, depletion of β-catenin by siRNA treatment abolished GnRH-II-induced MT1-MMP synthesis and reduced their invasive potential. Furthermore, siRNA-mediated reduction of MT1-MMP levels reduced GnRH-II-induced invasion in ovarian cancer cells. We therefore conclude that GnRH-II stimulates the PI3K/Akt pathway, and the phosphorylation of GSK3β, thereby enhancing the β-catenin-dependent up-regulation of MT1-MMP production, which contributes to ovarian cancer metastasis.

Emerging gonadotropin-releasing hormone agonists

INTRODUCTION

Gonadotropin-releasing hormone agonist analogs (GnRHa) are peptides that mimic the action of gonadotropin-releasing hormone (GnRH) and are used to suppress subsequent sex steroid production. Although the analogs are a rather defined group of drugs, there have been developments in the past decades and there is still ample room for improvement. New therapeutic strategies in the use of GnRHs are discussed.

AREAS COVERED

Major points of discussion include: i) the use of concomitant treatment of early breast cancer in premenopausal estrogen-positive and -negative patients, ii) the use of GnRHa for fertility preservation in young female patients with malignant diseases and iii) the use of GnRH analogs in assisted reproduction. The manuscript provides a better understanding of GnRH agonists as well as an explanation of their major indications, biochemical pathways and concluding therapeutic strategies. Recent results from international meetings and debates are described to explain current controversies.

EXPERT OPINION

This paper highlights the need for more complex GnRH analogs. In the next few years, there will be longer acting GnRHas that may improve adherence. New therapeutic targets in oncological concepts may go beyond fertility preservation and focus on the antiproliferative effects of GnRH analogs.

37-kDa laminin receptor precursor mediates GnRH-II-induced MMP-2 expression and invasiveness in ovarian cancer cells

GnRH-II enhances ovarian cancer cell invasion in an autocrine manner. We have now found that GnRH-II increases 37-kDa laminin receptor precursor (LRP) production in GnRH receptor (GnRHR)-positive OVCAR-3 and CaOV-3 ovarian cancer cells, while small interfering RNA (siRNA)-mediated depletion of GnRH-II or GnRHR mRNA abrogates this. The invasiveness of ovarian cancer cells is also reduced >85% by siRNA-mediated knockdown of LRP levels and >50% by pretreatment of Matrigel with a synthetic peptide that blocks interactions between laminin and the 67-kDa nonintegrin laminin receptor which comprises two LRP subunits. Conversely, overexpressing LRP in CaOV-3 cells increases their invasiveness 5-fold, while overexpressing LRP with a nonfunctional laminin-binding site does not. Depletion of LRP by siRNA treatment reduces CaOV-3 cell attachment to laminin-coated plates by ∼80% but only reduces their binding to Matrigel by ∼20%. Thus, while LRP influences CaOV-3 cell adhesion to laminin, LRP must act in other ways to enhance invasion. Matrix metalloproteinases (MMPs) are key mediators of invasion, and LRP siRNA treatment of OVCAR-3 and CaOV-3 cells inhibits MMP-2 but not MMP-9 mRNA levels. Overexpressing LRP in these cells increases MMP-2 production specifically, while a laminin-binding deficient LRP does not. Importantly, LRP siRNA treatment abolishes GnRH-II-induced MMP-2 production, and invasion in OVCAR-3 and CaOV-3 cells, which was also seen after MMP-2 siRNA treatment. These results suggest that GnRH-II-induced LRP expression increases the amount of the 67-kDa nonintegrin laminin receptor, which appears to interact with laminin in the extracellular matrix to promote MMP-2 expression and enhance ovarian cancer cell invasion.

Growth inhibition of tumor cells in vitro by using monoclonal antibodies against gonadotropin-releasing hormone receptor

As the continuation of a previous study, synthetic peptides corresponding to the extracellular domains of human gonadotropin-releasing hormone (GnRH) receptor were used to generate additional monoclonal antibodies which were further characterized biochemically and immunologically. Among those identified to recognize GnRH receptor, monoclonal antibodies designated as GHR-103, GHR-106 and GHR-114 were found to exhibit high affinity (Kd < or = 1 x 10(-8) M) and specificity to GnRH receptor as judged by the whole cell binding immunoassay and Western blot assay. Both anti-GnRH receptor monoclonal antibodies and GnRH were shown to compete for the same binding site of GnRH receptor on the surface of cultured cancer cells. Growth inhibitions of cancer cells cultured in vitro were demonstrated by cellular apoptosis experiments (TUNEL and MTT assays) under different conditions of treatment with GHR-106 monoclonal antibody or GnRH analogs. It was generally observed that both GnRH I and GHR-106 effectively induce the apoptosis of cultured cancer cells as determined by TUNEL and MTT assays. Consistently, suppressions of gene expressions at mRNA levels were demonstrated with several ribosomal proteins (P0, P1, P2 and L37), when cancer cells were incubated with GnRH or GHR-106. The widespread expressions of GnRH receptor in almost all of the studied human cancer cell lines were also demonstrated by RT-PCR and Western blot assay, as well as indirect immunofluorescence assay with either of these monoclonal antibodies as the primary antibody. In view of the longer half life of antibodies as compared to that of GnRH or its analogs, anti-GnRH receptor monoclonal antibodies in humanized forms could function as GnRH analogs and serve as an ideal candidate of anti-cancer drugs for therapeutic treatments of various cancers in humans as well as for fertility regulations.

Epidermal growth factor-induced GnRH-II synthesis contributes to ovarian cancer cell invasion

GnRH-II modulates ovarian cancer cells invasion and is expressed in normal ovary and ovarian epithelial cancer cells; however, the upstream regulator(s) of GnRH-II expression in these cells remains unclear. We now demonstrate that epidermal growth factor (EGF) increases GnRH-II mRNA levels in several human ovarian carcinoma cell lines and up-regulates GnRH-II promoter activity in OVCAR-3 cells in a dose-dependent manner, whereas an EGF receptor inhibitor (AG148) abolishes EGF-induced increases in GnRH-II promoter activity and GnRH-II mRNA levels. EGF increases the phosphorylation of cAMP-responsive element-binding protein (p-CREB) and its association with the coregulator, CCAAT/enhancer binding protein beta, whereas blocking the EGF-induced ERK1/2 phosphorylation with MAPK inhibitors (PD98059/U0126) markedly reduced these effects. Moreover, depletion of CREB using small interfering RNA attenuated EGF-induced GnRH-II promoter activity. Chromatin immunoprecipitation assays demonstrated that EGF induces p-CREB binding to a cAMP responsive-element within the GnRH-II promoter, likely in association with CCAAT/enhancer binding protein beta, and mutagenesis of this cAMP responsive-element prevented EGF-induced GnRH-II promoter activity in OVCAR-3 cells. Importantly, GnRH-II acts additively with EGF to promote invasion of OVCAR-3 and CaOV-3 cells, but not SKOV-3 cells that express low levels of GnRH receptor (GnRHR). Treatment with GnRHR small interfering RNA also partially inhibited the EGF-induced invasion of OVCAR-3 and CaOV-3 cells. Furthermore, EGF treatment transiently increases GnRHR levels in OVCAR-3 and CaOV-3, which likely accentuates the effects of increase GnRH-II production on cell invasion. These results provide evidence that EGF is an upstream regulator of the autocrine actions of GnRH-II on the invasive properties of ovarian cancer cells.