Expression of gonadotropin-releasing hormone receptor mRNA in the rat ventral prostate and dunning R3327 PAP adenocarcinoma before and after castration

The targeted LHRH analog AEZS-108 alters expression of genes related to angiogenesis and development of metastasis in uveal melanoma

Uveal melanoma (UM) is the most common malignant tumor of the eye. Recently, we have established that 46% of UM specimens express LHRH receptors. This finding supports the idea of a LHRH receptor-targeted therapy of UM patients. Cytotoxic analog of LHRH, AEZS-108 exhibits effective anti-cancer activity in LHRH-receptor positive cancers. AEZS-108 is a hybrid molecule, composed of a synthetic peptide carrier and the cytotoxic doxorubicin (DOX). In the present study, we investigated AEZS-108 induced cytotoxicity and the altered mRNA expression profile of regulatory factors related to angiogenesis and metastasis in LHRH receptor positive OCM3 cells. Our results show that AEZS-108 upregulates the expression of MASPIN/SERPINB5 tumor suppressor gene, which is downregulated in normal uvea and UM specimens independently from the LHRH receptor-ligand interaction. AEZS-108 also substantially downregulates hypoxia-inducible factor 1 alpha (HIF1A) expression. In order to investigate the mechanism of the induction of MASPIN by AEZS-108, OCM3 cells were treated with free DOX, D-Lys⁶ LHRH analog, or AEZS-108. qRT- PCR analysis revealed in OCM3 cells that AEZS-108 is a more potent inducer of MASPIN than free DOX. In conclusion, we show for the first time that AEZS-108 has a major impact in the regulation of angiogenesis thus plays a potential role in tumor suppression. Taken together, our results support the development of novel therapeutic strategies for UM focusing on LHRH receptors.

Gonadotropin-releasing hormone neuropeptides and receptor in human breast cancer: correlation to poor prognosis parameters

Expression of the two gonadotropin-releasing hormone homologue peptides GnRHI and GnRHII and their receptor GnRHR has been demonstrated in a number of malignancies. In hormone-dependent breast cancer, GnRH analogs are used for therapy in premenopausal women. Gene expression of GnRHI, II and R was studied in breast biopsies from primary breast adenocarcinoma obtained from the tumor and the adjacent benign tissue. Levels were evaluated by a multiplex real-time RT-PCR. GnRHI transcripts were detected in 14.7% of the benign and 29.4% malignant biopsies and GnRHII in 21.2% benign and 44.1% malignant biopsies. GnRHR was also more frequent in the malignant (54.2%) than in the benign (24.0%) biopsies, at similar expression levels. No transcripts were detected in biopsies from healthy individuals. There was a strong correlation between the presence of GnRHI and GnRHII transcripts and their receptor in the benign and the malignant biopsies. GnRHI, II and R expression correlated significantly with poor prognosis pathological parameters. Immunohistochemistry for GnRHR revealed expression in malignant cells and in epithelial cells of mammary ducts of the adjacent area with pre-cancerous features. In contrast, GnRH I and II peptides were rarely expressed at low levels in breast cancer cells. In conclusion GnRH peptides and receptor are expressed more frequently in breast tumors than in the adjacent mammary tissue, representing a malignant feature. Their expression correlated to tumor characteristics of poor prognosis and was therefore related to more aggressive malignancies. Concomitant expression of peptides and receptor supports an autocrine/paracrine regulating role.

Baculoviruses as gene therapy vectors for human prostate cancer

Prostate cancer is the most commonly diagnosed cancer in ageing men in the western world. While the primary cancers can be treated with androgen ablation, radiotherapy and surgery, recurrent castration resistant cancers have an extremely poor prognosis, hence promoting research that could lead to a better treatment. Targeted therapeutic gene therapy may provide an attractive option for these patients. By exploiting the natural ability of viruses to target and transfer their genes into cancer cells, either naturally or after genetic manipulation, new generations of biological control can be developed. In this review we present the advantages and practicalities of using baculovirus as a vector for prostate cancer gene therapy and provide evidence for the potential of the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) as a safer alternative vehicle for targeting cancer cells. Strategies to target baculovirus binding specifically to prostate cell surfaces are also presented. The large insertion capacity of baculoviruses also permits restricted, prostate-specific gene expression of therapeutic genes by cloning extended human transcriptional control sequences into the baculovirus genome.

GnRH receptor expression in human prostate cancer cells is affected by hormones and growth factors

GnRH receptors (GnRH-R) have been found in various malignancies, including prostate cancer (PCa). They mediate the direct antitumor effects of GnRH analogs. Nevertheless, few reports concern drug-induced modulation of GnRH-R levels. In this study, we investigated GnRH-R expression in androgen-sensitive (LNCaP) and -insensitive (PC-3) PCa cells treated for 4 and 6 days with a GnRH agonist (Leuprorelin acetate, LA, 10(-11) or 10(-6) M), Dihydrotestosterone (DHT, 10(-9) M), Cyproterone acetate (CA, 10(-7) M), and Epidermal growth factor (EGF, 10 ng/ml), either alone or combined. The RT-PCR analysis showed no variation in GnRH-R mRNA levels of both treated LNCaP and PC-3 cells. On the contrary, immunoblotting indicated that in LNCaP and PC-3 cells, LA upregulated membrane GnRH-R expression (up to 92%). In androgen-sensitive cells, DHT induced a GnRH-R increase (up to 119%) always comparable to that occurring in the presence of CA. GnRH-R upregulation by LA/DHT or CA/DHT association was similar to that promoted by the single agents. In PC-3 cells, EGF upregulated GnRH-R (up to 110%). A prolonged treatment (for 12 days) determined a greater EGF-induced increase in GnRH-R levels (142%). Lower (or no) receptor enhancement occurred when LA and EGF were associated. Our findings indicate that LA post-transcriptionally upregulates its own membrane receptor in androgen-sensitive and -insensitive PCa cells, counteracting the receptor enhancement produced by DHT and EGF. The effects, obtained with a relatively long and continuous treatment, may have implications in the choice of therapy modality with GnRH analogs and may render the receptor a novel therapeutic target, particularly in hormone-refractory PCa.

Alteration of gonadotropin-releasing hormone receptor expression with the progression of prostate cancer in the Dunning rat adenocarcinoma sublines

Inhibitory effects of GnRH analogues on tumour growth in vitro suggests that such direct effects may be of importance also in vivo. However, the role of GnRH receptors (GnRH-R) in prostate tumour progression is largely unknown. The aim was therefore to investigate the variation of GnRH-R expression with prostate tumour progression using Dunning rat adenocarcinoma sublines representing different prostate tumour grades. GnRH-R levels were quantified in the rat dorsolateral (DLP) and Dunning sublines (PAP, AT-1, AT-2, AT-3, MatLyLu) using competitive RT-PCR and Western blot. The results showed that all Dunning sublines had significantly elevated GnRH-R mRNA expression levels compared with DLP. Comparison of GnRH-R mRNA levels between different tumour grades revealed no difference in mRNA expression. However, the anaplastic and highly metastatic AT-3 and MatLyLu tumours displayed a tendency for lower GnRH-R mRNA values than the non-metastatic tumour sublines. Our data demonstrate the expression of GnRH-R in normal rat DLP and in different Dunning sublines. However, GnRH-R seems not to be involved in tumour progression.

The clinical implications of the difference between castration, gonadotrophin releasing-hormone (GnRH) antagonists and agonist treatment on the morphology and expression of GnRH receptors in the rat ventral prostate

OBJECTIVE

To examine the effects of castration and continuous gonadotrophin releasing-hormone (GnRH) agonist and antagonist therapy on the expression of GnRH-receptors type I (GnRH-RI) in rat ventral prostate (VP) and pituitary tissue, and to compare the effects on prostate morphology.

MATERIAL AND METHODS

Mature Sprague-Dawley rats were assigned to four treatment groups: group 1, vehicle only; group 2, GnRH agonist goserelin (100 microg/rat/day); group 3, GnRH antagonist cetrorelix (100 microg/rat/day); and group 4, orchidectomy. After 4 weeks the body weights were recorded and VP and pituitary tissue analysed for GnRH-RI expression using a competitive reverse transcriptase-polymerase chain reaction and immunohistochemistry.

RESULTS

GnRH antagonist and orchidectomy decreased testosterone secretion and VP volume similarly, but the effects were not identical. The involution of the glandular lumina was more pronounced after orchidectomy while the antagonist therapy was more effective in suppressing epithelial cell proliferation. In the VP, GnRH-RI mRNA levels were increased after GnRH analogue therapy, but were unaffected by orchidectomy. In the pituitary, GnRH-RI mRNA expression was higher in response to orchidectomy and decreased after GnRH analogue treatment.

CONCLUSION

Treatment with a GnRH antagonist for 4 weeks is more effective than an agonist in suppressing testosterone and inducing VP involution. The GnRH antagonist was more effective in suppressing VP epithelial cell proliferation than was castration, suggesting that it induces reduced proliferation by interfering with effects of locally produced GnRH. These results suggest that different regulatory mechanisms may operate in the rat VP than in the pituitary to control GnRH-RI mRNA expression.

Receptor gene messenger RNA expression in metastatic lesions of prostate cancer

PURPOSE

There are hardly any options for treating hormone refractory prostate cancer. Some groups have already suggested antitumor therapy of prostate cancer using agonists, antagonists or other concepts acting on luteinizing hormone-releasing hormone (LH-RH) receptor. Few studies have been published to date on the detection of LH-RH receptors in human prostate cancer tissue. However, at this point it is completely unclear in this context whether metastasizing prostate cancer lesions, which may be major potential targets of a type of therapy, have any LH-RH receptors. In this study we examined tumor samples of lymph nodes from patients with prostate cancer obtained during radical prostatectomy and laparoscopic lymphadenectomy for the expression of LH-RH receptor messenger (m)RNA.

MATERIALS AND METHODS

Multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) was done to detect the expression of the mRNA of LH-RH receptor, prostate specific antigen and beta-actin in pelvic lymph nodes from 100 patients with prostate cancer.

RESULTS

In 27 patients at least 1 histopathological metastasis (19) and/or positive RT-PCR for prostate specific antigen (22) was identified. In 7 of these patients (25.9%) RT-PCR revealed LH-RH mRNA expression.

CONCLUSIONS

To our knowledge our study shows for the first time a rather low incidence of LH-RH receptor mRNA in primary pelvic lymph node metastases. However, since other studies show that an increased incidence of LH-RH receptors is typical of the hormone refractory stage of the disease, further studies in this specific patient population may help explain the clinical importance of LH-RH receptors in the development of new therapeutic approaches to advanced prostate cancer.

Gonadotropin-releasing hormone receptor expression in the human prostate

BACKGROUND

Inhibitory effects of gonadotropin-releasing hormone (GnRH) analogs on prostate cancer cell proliferation, both in vivo and in vitro, indicate the presence of specific binding sites for GnRH on prostate cancer cells. To investigate this issue further, we examined the expression of GnRH receptor (GnRH-R) mRNA and protein in human prostate biopsies as well as in other extrapituitary tissues.

METHODS

The relative quantity of GnRH-R mRNA was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC) in human prostate biopsies. Extrapituitary GnRH-R levels were determined by a semiquantitative PCR reaction.

RESULTS

Using PCR, a relatively high expression level of GnRH-R mRNA was found in prostate tumor tissue followed by normal prostate, thymus, and kidney expression levels. The levels showed by heart, brain, placenta, lung, liver, skeletal muscle, pancreas, colon, ovary, small intestine, spleen, and testis were low but detectable, whereas peripheral blood leukocyte showed no demonstrable product. GnRH-R immunoreactivity was localized in both luminal and basal epithelial cells in benign and malignant prostate tissue, and GnRH-R were also observed in intraprostatic lymphocytes. The relative GnRH-R mRNA levels in prostate biopsies from 16 patients showed a wide range of individual differences, but these differences were not related to histological grade. Castration therapy did not significantly influence GnRH-R mRNA expression in normal and malignant prostate tissue.

CONCLUSIONS

These results suggest that epithelial cells and infiltrating lymphocytes are targets for GnRH action in the human prostate. Comparative data show relatively high GnRH-R expression in human prostate tissue compared to other human tissues.