Human renal cell carcinoma expresses distinct binding sites for growth hormone-releasing hormone

Signaling mechanism of growth hormone-releasing hormone receptor

The hypothalamic peptide growth hormone-releasing hormone (GHRH) stimulates the secretion of growth hormone (GH) from the pituitary through binding and activation of the pituitary type of GHRH receptor (GHRH-R), which belongs to the family of G protein-coupled receptors with seven potential membrane-spanning domains. Splice variants of GHRH-Rs (SV) in human tumors and other extra pituitary tissues were identified and their cDNA was sequenced. Among the SVs, splice variant 1 (SV1) possesses the greatest similarity to the full-length GHRH-R and remains functional by eliciting cAMP signaling and mitogenic activity upon GHRH stimulation. A large body of work have evaluated potential clinical applications of agonists and antagonists of GHRH in diverse fields, including endocrinology, oncology, cardiology, diabetes, obesity, metabolic dysfunctions, Alzheimer's disease, ophthalmology, wound healing and other applications. In this chapter, we briefly review the expression and potential function of GHRH-Rs and their SVs in various tissues and also elucidate and summarize the activation, molecular mechanism and signalization pathways of these receptors. Therapeutic applications of GHRH analogs are also discussed.

Splice variant of growth hormone-releasing hormone receptor drives esophageal squamous cell carcinoma conferring a therapeutic target

An explanation has been lacking for the suppressive action of antagonists of growth hormone-releasing hormone receptors (GHRH-Rs) on cancers that do not express GHRH-Rs, an established target of the antagonists. We demonstrate here that esophageal squamous cell carcinoma (ESCC), a representative cancer type that barely expresses GHRH-Rs, responds to GHRH-R antagonists. Hypoxia induces GHRH-R splice variant 1 (SV1) and activates a key glycolytic enzyme. Glycolytic metabolism and tumor progression are promoted by activation of SV1 and reversed by the GHRH-R antagonist MIA-602. A high expression of SV1 in ESCC patients predicts a poor prognosis. These findings document the importance of SV1 as a target of GHRH-R antagonists and underline the therapeutic potential of GHRH-R antagonists against SV1-expressing cancers.

The extrahypothalamic growth hormone-releasing hormone (GHRH) and its cognate receptors (GHRH-Rs) and splice variants are expressed in a variety of cancers. It has been shown that the pituitary type of GHRH-R (pGHRH-R) mediates the inhibition of tumor growth induced by GHRH-R antagonists. However, GHRH-R antagonists can also suppress some cancers that do not express pGHRH-R, yet the underlying mechanisms have not been determined. Here, using human esophageal squamous cell carcinoma (ESCC) as a model, we were able to reveal that SV1, a known splice variant of GHRH-R, is responsible for the inhibition induced by GHRH-R antagonist MIA-602. We demonstrated that GHRH-R splice variant 1 (SV1) is a hypoxia-driven promoter of tumor progression. Hypoxia-elevated SV1 activates a key glycolytic enzyme, muscle-type phosphofructokinase (PFKM), through the nuclear factor kappa B (NF-κB) pathway, which enhances glycolytic metabolism and promotes progression of ESCC. The malignant actions induced by the SV1–NF-κB–PFKM pathway could be reversed by MIA-602. Altogether, our studies demonstrate a mechanism by which GHRH-R antagonists target SV1. Our findings suggest that SV1 is a hypoxia-induced oncogenic promoter which can be an alternative target of GHRH-R antagonists.

Prognostic role of HPV infection in esophageal squamous cell carcinoma

Background

The aims of this study were to evaluate whether HPV infection has a prognostic role in patients with esophageal squamous cell carcinoma who underwent oncological treatment and also to compare the heat shock proteins (Hsp) 90, 27 and 16.2 and growth hormone-releasing hormone receptor (GHRH-R) expression patterns of the pre-treatment tumor biopsies with the HPV status and with the oncological response.

Methods

Pre-treatment tumor biopsies of 74 patients with locally advanced esophageal squamous cell carcinoma were processed retrospectively. The presence of HPV was detected by chromogenic in situ hybridization. Hsp and GHRH-R expressions were determined using immunohistochemistry. Following neoadjuvant or definitive radiochemotherapy, the patients were restaged according to the Response Evaluation Criteria in Solid Tumors. The correlation between the HPV status, response to treatment and Hsp and GHRH-R expressions were evaluated.

Results

Fourteen (19%) patients were HPV-positive. These patients were more likely to respond poorly to multimodal therapy (71.4% were non-responders vs. 28.6% responders) and had shorter survival compared to HPV-negative patients (mean survival of 8 months vs. 11 months), although the difference was not significant. A significantly higher number of HPV-positive patients expressed Hsp 90 and 16.2 at high levels (93 and 79%, respectively) than at low levels (Chi-Square p = 0.019 and p = 0.031). Higher levels of Hsp expressions were associated with poorer response to therapy and worse overall survival. No correlation was found between GHRH-R expression and the HPV status, nor between GHRH-R expression and the treatment response of the examined samples.

Conclusions

We found that HPV infection was associated with poor response to oncological treatment and decreased overall survival, and therefore proved to be a negative prognostic factor in patients with esophageal squamous cell carcinoma. There was a linear correlation between levels of Hsp 90 and 16.2 expression and HPV positivity.

Possible Predictive Markers of Response to Therapy in Esophageal Squamous Cell Cancer

The aim of the present study was to investigate the relationship between the intensity of biomarker expression and the response to radiochemotherapy in patients with advanced esophageal squamous cell cancer (ESCC). Ninety-two patients with locally advanced ESCC were examined retrospectively. Pre-treatment tumor samples were stained for proteins SOUL, Hsp 16.2, Growth Hormone-Releasing Hormone Receptor (GHRH-R) and p-Akt using immunhistochemistry methods. Kaplan-Meier curves were used to show the relationship between intensity of expression of biomarkers and clinical parameters and 3-year OS. A significant correlation was found between high intensity staining for Hsp 16.2, p-Akt and SOUL and poor response to NRCT. Application of a higher dose of radiation and higher dose of cisplatin resulted in better clinical and histopathological responses, respectively. Among the clinical parameters, the localization of the tumor in the upper-third of the esophagus and less than 10% weight loss were independent prognostic factors for increased 3-year OS. Hsp16.2, p-Akt and SOUL are predictors of negative response to NRCT, therefore these biomarkers may become promising targets for therapy. Furthermore, level of expression of p-Akt, weight loss and the localization of the tumor are significant factors in the prediction of OS in ESCC.

Future perspectives for mTOR inhibitors in renal cell cancer treatment

ABSTRACT 

Everolimus is a mTOR inhibitor that demonstrates antitumor and antiangiogenic activities. In a randomized Phase III trial, patients with metastatic renal cell carcinoma who progressed on sunitinib/sorafenib were treated with everolimus and showed significant improvement in progression-free survival compared with best supportive care. Novel approaches in treatment are expected to ensure less toxic therapies and increase efficacy of everolimus. To provide a new perspective for mTOR inhibitor research and therapy, we discuss renal cell carcinoma cancer stem cells as a potential target for mTOR inhibitors and present new concepts on emerging antiangiogenic therapies. Finally, we point why systems biology approach with reverse molecular engineering may also contribute to the field of drug discovery in renal cell carcinoma.

Lymphocyte GH-axis hormones in immunity

The production and utilization of common ligands and their receptors by cells of the immune and neuroendocrine systems constitutes a biochemical information circuit between and within the immune and neuroendocrine systems. The sharing of ligands and receptors allows the immune system to serve as the sixth sense notifying the nervous system of the presence of foreign entities. Within this framework, it is also clear that immune cell functions can be altered by neuroendocrine hormones and that cells of the immune system have the ability to produce neuroendocrine hormones. This review summarizes a part of this knowledge with particular emphasis on growth hormone (GH). The past two decades have uncovered a lot of detail about the actions of GH, acting through its receptor, at the molecular and cellular level and its influence on the immune system. The production and action of immune cell-derived GH is less well developed although its important role in immunity is also slowly emerging. Here we discuss the production of GH, GH-releasing hormone (GHRH) and insulin-like growth factor-1 (IGF-1) and their cognate receptors on cells of the immune system and their influence via endocrine/autocrine/paracrine and intracrine pathways on immune function. The intracellular mechanisms of action of immune cell-derived GH are still largely unexplored, and it is anticipated that further work in this particular area will establish an important role for this source of GH in normal physiology and in pathologic situations.

Expression of lymphocyte-derived growth hormone (GH) and GH-releasing hormone receptors in aging rats

In the present study, we show that higher levels of lymphocyte GH are expressed in spleen cells from aging animals compared to young animals. Further, leukocytes from primary and secondary immune tissues and splenic T and B cells from aging rats all express higher levels of GHRH receptors compared to younger animals. Bone marrow and splenic T cells express the highest levels of GHRH receptor in aging animals. Spleen cells from aging animals showed no significant change in proliferation or GH induction after treatment with GHRH. Taken together, the data for the first time show alterations in GH synthesis and expression of the GHRH receptor on cells of the immune system that may play a role in the immune response in aging.

Comparison of expression of growth hormone-releasing hormone and its receptor splice variant 1 in different stages of endometriosis

BACKGROUND

The present study aims to explore the significance of the expression of growth hormone-releasing hormone (GHRH) and its receptor splice variant 1 (GHRHSV1) in endometriosis (EM).

MATERIALS AND METHODS

In this research paper 80 EM patients who received treatment between March 2009 and September 2010 were selected, among which 20 were in stages I, II, III and IV respectively. 50 non-EM patients who underwent hysterectomy because of myoma during the same period comprised the control group. GHRH, GHRH-SV1 and their corresponding mRNA expression in eutopic endometrium and endometriotic tissue as well as ectopic endometrium were detected using immunohistochemical streptavidin-peroxidase (SP) and RT-PCR methods. Analysis of Variance (ANOVA) with Tukey Post Hoc test was used for data analysis and p<0.05 was considered significant.

RESULTS

GHRH, GHRH-SV1 and their corresponding mRNA were expressed in eutopic endometrium and endometriotic tissue as well as ectopic endometrium. The mean optical density (OD) values of the GHRH and GHRH-SV1 expression in the experimental group were significantly higher than those in the normal group (p<0.05), and the relative intensity (RI) of GHRH mRNA and GHRH-SV1 mRNA expression in the experimental group was also significantly higher (p<0.05). The mean OD values of the GHRH and GHRHSV1 expression showed significant differences among endometriotic tissue at different stages of EM (p<0.05), and the RI of GHRH and GHRH-SV1 mRNA expression also showed significant differences (p<0.05).

CONCLUSION

GHRH and GHRH-SV1 expression levels differ significantly at different stages of endometriosis.

Vasoactive intestinal peptide (VIP) inhibits human renal cell carcinoma proliferation

Clear renal cell carcinoma (cRCC) is an aggressive and fatal neoplasm. The present work was undertaken to investigate the antiproliferative potential of vasoactive intestinal peptide (VIP) exposure on non-tumoral (HK2) and tumoral (A498, cRCC) human proximal tubular epithelial cell lines. Reverse transcription and semiquantitative PCR was used at the VIP mRNA level whereas enzyme immunoanalysis was performed at the protein level. Both renal cell lines expressed VIP as well as VIP/pituitary adenylate cyclase-activating peptide (VPAC) receptors whereas only HK2 cells expressed formyl peptide receptor-like 1 (FPRL-1). Receptors were functional, as shown by VIP stimulation of adenylyl cyclase activity. Treatment with 0.1μM VIP (24h) inhibited proliferation of A498 but not HK2 cells as based on a reduction in the incorporation of [(3)H]-thymidine and BrdU (5'-Br-2'-deoxyuridine), PCNA (proliferating-cell nuclear antigen) expression and STAT3 (signal transducer and activator of transcription 3) expression and activation. VPAC(1)-receptor participation was established using JV-1-53 antagonist and siRNA transfection. Growth-inhibitory response to VIP was related to the cyclic adenosine monophosphate (cAMP)/exchange protein directly activated by cAMP (EPAC)/phosphoinositide 3-kinase (PI3-K) signaling systems as shown by studies on adenylate cyclase stimulation, and using the EPAC-specific compound 8CPT-2Me-cAMP and specific kinase inhibitors such as H89, wortmannin and PD98059. The efficacy of VIP on the prevention of tumor progression was confirmed in vivo using xenografted athymic mouse. These actions support a potential role of this peptide and its agonists in new therapies for cRCC.

The effect of GHRH antagonists on human glioblastomas and their mechanism of action

The effects of new growth hormone-releasing hormone (GHRH) antagonists JMR-132 and MIA-602 and their mechanism of action were investigated on 2 human glioblastoma cell lines, DBTRG-05 and U-87MG, in vitro and in vivo. GHRH receptors and their main splice variant, SV1 were found on both cell lines. After treatment with JMR-132 or MIA-602, the cell viability decreased significantly. A major decrease in the levels of phospho-Akt, phospho-GSK3β and phosho-ERK 1/2 was detected at 5 and 10 min following treatment with the GHRH antagonists, whereas elevated levels of phospho-p38 were observed at 24 hr. The expression of caspase-3 and poly(ADP-ribose) (PARP), as the downstream executioners of apoptosis were found to be significantly elevated after treatment. Following treatment of the glioblastoma cells with GHRH antagonists, nuclear translocation of apoptosis inducing factor (AIF) and Endonuclease G (Endo G) and the mitochondrial release of cytochrome c (cyt c) were detected, indicating that the cells were undergoing apoptosis. In cells treated with GHRH antagonists, the collapse of the mitochondrial membrane potential was shown with fluorescence microscopy and JC-1 membrane potential sensitive dye. There were no significant differences between results obtained in DBTRG-05 or U-87MG cell lines. After treatment with MIA-602 and JMR-132, the reduction rate in the growth of DBTRG-05 glioblastoma, xenografted into nude mice, was significant and tumor doubling time was also significantly extended when compared with controls. Our study demonstrates that GHRH antagonists induce apoptosis through key proapoptotic pathways and shows the efficacy of MIA-602 for experimental treatment of glioblastoma.

A correlation of endocrine and anticancer effects of some antagonists of GHRH

GHRH receptor antagonists inhibit growth and metastasis of a large number of experimental tumors expressing the pituitary GHRH receptor (pGHRH-R) and its major splice variant SV1. In this study, using Western blot, we demonstrated that DBTRG-05 and U-87MG human glioblastoma cell lines express pGHRH-R at levels 6-15 times higher than SV1. To reveal a correlation between the anticancer activity and the endocrine potency on inhibition of GH release, we compared the antitumor effect of GHRH antagonists JV-1-63 and MZJ-7-138 on growth of DBTRG-05 human glioblastomas grafted into athymic nude mice with their inhibitory potency on GH release. JV-1-63 strongly suppressed the stimulated GH secretion induced by clonidine in rats and inhibited the exogenous GHRH-induced GH surge by 88-99% in vivo and in vitro. MZJ-7-138 decreased the stimulated GH secretion by 58% in vitro and showed only a tendency to inhibit GH secretion in vivo. The strong inhibitor of GH release JV-1-63 reduced tumor growth of DBTRG-05 glioblastomas in nude mice by 46%, while the weak GH release suppressor MZJ-7-138 did not have an effect. Exposure of DBTRG-05 cells to the GHRH antagonists in vitro caused an upregulation of mRNA expression for pGHRH-R and a downregulation of SV1 expression, with JV-1-63 having significantly greater effects than MZJ-7-138. Our results demonstrate that a positive correlation exists between the endocrine potency and the antiproliferative efficacy of GHRH antagonists in tumors strongly expressing pGHRH-R.

Growth hormone-releasing hormone antagonist induces apoptosis of human endometrial cancer cells through PKCδ-mediated activation of p53/p21

The growth hormone-releasing hormone (GHRH) antagonists have been shown to inhibit growth of human cancer cells, but the underlying molecular mechanisms and their actions have not been fully investigated. In this study, we first showed that GHRH-R splice variant 1 (SV1) was expressed in two human endometrial cancer cell lines, Ishikawa and ECC-1. By using MTT assay, immunoblotting for cleaved caspase-3 and TUNEL assays, we found that cell growth inhibition and apoptosis were induced in GHRH antagonist, JMR-132-treated cells by activating PKCδ and could be inhibited by treatment with PKC inhibitor, GF109203X. In addition, activation and protein expression of p53 as well as the expression of its downstream effector, p21, were increased by JMR-132 treatment. Moreover, JMR-132-induced p53 and p21 expression were diminished by treatment with PKC inhibitor. Knockdown of endogenous p53 and p21 by siRNAs abolished the JMR-132-induced cell growth inhibition and apoptosis. This study demonstrates a novel mechanism in which GHRH antagonist-induced cell growth inhibition and apoptosis through PKCδ-mediated activation of p53/p21 in human endometrial cancer cells. These findings may suggest the feasibility of GHRH antagonists as a therapeutic approach for human cancer.

GHRH antagonists reduce the invasive and metastatic potential of human cancer cell lines in vitro

We investigated the effect of a GHRH antagonist, MIA-602on the metastatic cascade in vitro of three human cancers, DBTRG-05 glioblastoma, MDA-MB-468 estrogen-independent breast, and ES-2 clear cell ovarian cancer. GHRH receptors and their main splice variant, SV1 were detected on all three cell lines. After treatment with MIA-602, the cell viability decreased significantly, significant inhibition of cell invasion was observed and the release of MMPs was significantly decreased. The attachment of cancer cells to fibronectin and matrigel was severely hindered. Wound-healing experiments demonstrated a reduced cellular motility in all three cell lines. The upregulation of caveolin-1 and E-cadherin,and thepowerful downregulation of NF-kappaB and beta-catenin was detected. Our study suggests that the clinical application of highly potent GHRH antagonists in cancer therapy would be desirable since they inhibit proliferation and metastasis development as well.

Expression and possible implication of growth hormone-releasing hormone receptor splice variant 1 in endometriosis

OBJECTIVE

To determine possible involvement of splice variant 1 (SV1), a variant of the pituitary growth hormone-releasing hormone (GHRH) receptor, in the development of endometriosis.

DESIGN

Comparative and laboratory study.

SETTING

University teaching hospital reproductive endocrinology and infertility practice.

PATIENT(S)

Eutopic and ectopic endometrial tissues, and peritoneal bone marrow-derived cells were collected from women with or without endometriosis. Normal ovarian tissues were collected from women without endometriosis.

INTERVENTION(S)

Ectopic endometrial stromal cells (ESC) were isolated and cultured with or without GHRH.

MAIN OUTCOME MEASURE(S)

Gene expression of GHRH and SV1 in the sample tissues was determined by reverse transcriptase (RT) nested polymerase chain reaction (PCR). Cyclic adenosine monophosphate (cAMP) production and 5-bromo-2'-deoxyuridine (BrdU) incorporation in ESC were measured using specific assay systems.

RESULT(S)

We detected SV1 messenger RNA (mRNA) in 17 out of 27 (63%) ectopic endometrial tissues, which was statistically significantly higher than that detected in eutopic endometrial tissues (2 out of 47, 4%) and normal ovarian tissues (0 out of 14). A relatively low rate of GHRH mRNA was detected in ectopic endometrial tissues (6 out of 27, 24%) and in eutopic endometrial tissues (12 out of 47, 26%). In contrast, relatively high rates were detected in normal ovarian tissues (14 out of 14, 100%) and peritoneal bone marrow-derived cells (13 out of 16, 81%). We found that GHRH stimulated the production of cAMP and the incorporation of BrdU in SV1-expressing ESC.

CONCLUSION(S)

GHRH and SV1 may play a role in promoting the development of endometriosis.

Knocking down gene expression for growth hormone-releasing hormone inhibits proliferation of human cancer cell lines

Splice Variant 1 (SV-1) of growth hormone-releasing hormone (GHRH) receptor, found in a wide range of human cancers and established human cancer cell lines, is a functional receptor with ligand-dependent and independent activity. In the present study, we demonstrated by western blots the presence of the SV1 of GHRH receptor and the production of GHRH in MDA-MB-468, MDA-MB-435S and T47D human breast cancer cell lines, LNCaP prostate cancer cell line as well as in NCI H838 non-small cell lung carcinoma. We have also shown that GHRH produced in the conditioned media of these cell lines is biologically active. We then inhibited the intrinsic production of GHRH in these cancer cell lines using si-RNA, specially designed for human GHRH. The knocking down of the GHRH gene expression suppressed the proliferation of T47D, MDA-MB-435S, MDA-MB-468 breast cancer, LNCaP prostate cancer and NCI H838 non-SCLC cell lines in vitro. However, the replacement of the knocked down GHRH expression by exogenous GHRH (1–29)NH₂ re-established the proliferation of the silenced cancer cell lines. Furthermore, the proliferation rate of untransfected cancer cell lines could be stimulated by GHRH (1–29)NH₂ and inhibited by GHRH antagonists MZ-5-156, MZ-4-71 and JMR-132. These results extend previous findings on the critical function of GHRH in tumorigenesis and support the role of GHRH as a tumour growth factor.

Antagonists of growth-hormone-releasing hormone: an emerging new therapy for cancer

This article reviews the potential clinical uses of antagonists of growth-hormone-releasing hormone (GHRH) for tumor therapy. GHRH antagonists suppress the growth of various human cancer lines xenografted into nude mice; such tumors include breast, ovarian, endometrial and prostate cancers, lung cancers (small-cell lung carcinomas and non-small-cell lung carcinomas), renal, pancreatic, gastric and colorectal carcinomas, brain tumors (malignant gliomas), osteogenic sarcomas and non-Hodgkin's lymphomas. The antitumor effects of GHRH antagonists are exerted in part indirectly through the inhibition of the secretion of GH from the pituitary and the resulting reduction in the levels of hepatic insulin-like growth factor I (IGF-I). The main effects of the GHRH antagonists are, however, exerted directly on tumors. GHRH ligand is present in various human cancers and might function as an autocrine and/or paracrine growth factor. Pituitary-type GHRH receptors and their splice variants are also found in many human cancers. The inhibitory effects of GHRH antagonists seem to be due to the blockade of action of tumoral GHRH. Antagonists of GHRH can also suppress cancer growth by blocking production of IGF-I and/or IGF-II by the tumor. Further development of GHRH antagonists that are still-more potent should lead to potential therapeutic agents for various cancers.

The combination of antagonists of LHRH with antagonists of GHRH improves inhibition of androgen sensitive MDA-PCa-2b and LuCaP-35 prostate cancers

BACKGROUND

Antagonists of growth hormone-releasing hormone (GHRH) could extend the duration of response of androgen sensitive prostate cancers to androgen deprivation.

METHODS

We investigated the effect of new GHRH antagonists MZ-J-7-118 and MZ-J-7-138 and luteinizing hormone-releasing hormone (LHRH) antagonist Cetrorelix or castration on androgen sensitive MDA-PCa-2b and LuCaP-35 prostate cancer models xenografted into nude mice. Animals bearing androgen-independent LuCaP-35V prostatic cancer model were also treated with MZ-J-7-118.

RESULTS

Receptors for LHRH and GHRH were present in MDA-PCA-2b, LuCaP-35, and LuCaP-35V tumors. GHRH antagonists increased the inhibitory effect of surgical castration and LHRH antagonists on androgen sensitive MDA-PCa-2b and LuCaP-35 tumors. The time to relapse of androgen-dependent LuCaP-35 tumors was extended by GHRH antagonists. Growth of androgen-independent LuCaP-35V xenografts was also significantly inhibited by MZ-J-7-118. In MDA-PCa-2b tumors treatment with MZ-J-7-118 caused a significant decrease of VEGF and Cetrorelix or its combination with MZ-J-7-118 reduced EGF. The B(max) of EGF receptors was significantly reduced by Cetrorelix, MZ-J-7-118 and their combination.

CONCLUSIONS

Our findings suggest that the use of a combination of antagonists of GHRH and LHRH could improve the therapy for androgen sensitive prostate cancer. Antagonists of GHRH could be also considered for treatment of androgen-independent prostate cancers.

Synergistic inhibition of growth of lung carcinomas by antagonists of growth hormone-releasing hormone in combination with docetaxel

We investigated the effect of antagonists of growth hormone-releasing hormone (GHRH) MZ-J-7-138 and JV-1-92 on H460 human non-small cell lung carcinoma (NSCLC) xenografted orthotopically into nude mice. Treatment with MZ-J-7-138 or JV-1-92 inhibited orthotopic growth of H460 NSCLC by 52-65% (P < 0.001) and was associated with a significant decrease in protein expression of K-Ras, cyclooxygenase-2 (Cox-2) and phospho-Akt (pAkt). In other experiments, treatment with MZ-J-7-138 or docetaxel reduced tumor volume of s.c. xenografted H460 human NSCLC by 30-36% (P < 0.01). The combination of MZ-J-7-138 and docetaxel resulted in a synergistic growth inhibition of H460 NSCLC xenografts of 63%. MZ-J-7-138 alone or in combination with docetaxel significantly reduced protein levels of K-Ras, Cox-2, and pAkt by 56-63%. Docetaxel given singly diminished the protein levels only of Cox-2 and did not affect K-Ras and pAkt. High-affinity binding sites, mRNA, and protein expression of pituitary GHRH receptors and its splice variant (SV) 1 were found in H460. H460 NSCLC cells contained GHRH peptide, and its growth was significantly inhibited in vitro by 10 microM MZ-J-7-138 (P < 0.001). Serum insulin-like growth factor 1 (IGF1) was not reduced by either GHRH antagonists. These findings suggest that antiproliferative effects of GHRH antagonists in H460 NSCLC are associated with down-regulation of K-Ras, Cox-2, and pAkt. In conclusion, GHRH antagonists in combination with docetaxel synergistically inhibit growth of H460 NSCLC and the expression of K-ras, Cox-2, and pAkt, which might abrogate the signal transduction pathways for cell growth stimulation and therapeutic resistance.

Immunocytochemical localisation of plasma membrane GHRH receptors in human tumours using a novel anti-peptide antibody

Antagonists of growth hormone releasing hormone (GHRH) directly inhibit the growth of a variety of human neoplasms. However, the plasma membrane receptor mediating these effects has not been immunocytochemically visualised in primary tumour cells. Given that previous attempts using an antibody to the amino-terminal region did not result in the visualisation of plasma membrane receptors, we have developed and characterised an anti-peptide antibody to the carboxy-terminal region 403-422 of the human pituitary GHRH receptor. This sequence is identical to residues 339-358 of splice variant 1 (SV1) of tumoural GHRH receptors. Specificity of the antibody was demonstrated by (1) immunocytochemical staining of GHRH receptor-transfected cells, (2) detection of a broad glycosylated protein band migrating at Mr 50,000-60,000 in Western blots of membranes from human pituitary, and (3) abolition of tissue immunostaining by preadsorbtion of the antibody with its immunising peptide. The distribution of GHRH receptors was investigated in 69 formalin-fixed, paraffin-embedded human tumours showing that GHRH receptors were frequently expressed in breast, ovarian and prostate carcinomas. Immunoreactive GHRH receptors were clearly confined to the plasma membrane and uniformly present on nearly all tumour cells. In Western blots of membranes prepared from human tumours, the anti-GHRH receptor antibody detected a non-glycosylated protein band migrating at Mr 40,000, which corresponds to the expected molecular weight of splice variant 1 of tumoural GHRH receptors. Together, our findings provide direct evidence for the presence of GHRH receptor protein on the plasma membrane of primary human tumour cells. The GHRH receptor visualisation could be of value for a rapid immunohistochemical identification of those tumours which could be a target for diagnostic or therapeutic intervention using GHRH analogues.

The expression of the pituitary growth hormone-releasing hormone receptor and its splice variants in normal and neoplastic human tissues

Various attempts to detect human pituitary growth hormone-releasing hormone receptor (pGHRH-R) in neoplastic extrapituitary tissues have thus far failed. Recently, four splice variants (SVs) of GHRH-R have been described, of which SV1 has the highest structural homology to pGHRH-R and likely plays a role in tumor growth. The aim of this study was to reinvestigate whether human tumors and normal human extrapituitary tissues express the pGHRH-R and to corroborate our previous findings on its SVs. Thus, we developed a real-time PCR method for the detection of the mRNA for the pGHRH-R, its SVs, and the GHRH peptide. Using real-time PCR, Western blotting, and radioligand-binding assays, we detected the mRNA for pGHRH-R and pGHRH-R protein in various human cancer cell lines grown in nude mice and in surgical specimens of human lung cancers. The expression of mRNA for SVs of pGHRH-R and GHRH was likewise found in xenografts of human non-Hodgkin's lymphomas, pancreatic cancer, glioblastoma, small-cell lung carcinomas, and in human nonmalignant prostate, liver, lung, kidney, and pituitary. Western blots showed that these normal and malignant human tissues contain SV1 protein and immunoreactive GHRH. Our results demonstrate that some normal human tissues and tumors express mRNA and protein for the pGHRH-R and its splice variants. These findings confirm and extend the concept that GHRH and its receptors play an important role in the pathophysiology of human cancers.

Antagonists of growth hormone releasing hormone and bombesin inhibit the expression of EGF/HER receptor family in H-69 small cell lung carcinoma

Effects of in vivo treatment with antagonists of growth hormone-releasing hormone (GHRH), JV-1-65 and MZ-J-7-110, and bombesin/gastrin-releasing peptide antagonist RC-3940-II, on the EGF receptor (EGFR) family, were investigated in H-69 SCLC. Tumors were analyzed by RT-PCR, immunoblotting and binding assays. Treatment with these analogs reduced the binding capacity of EGFR by 18-64%, and inhibited the mRNA expression for EGFR, HER-2 and -3 by 27-75.4, 17-26.3, and 13.8-46.6%, respectively. The antagonists also decreased the protein levels for EGFR by 21-34%, HER-2 by 36-68% and HER-3 by 43-49%. This is the first demonstration that antiproliferative effects of GHRH antagonists are associated with a downregulation of EGF/HER receptors.

Antagonists of growth hormone-releasing hormone cross the blood-brain barrier: a potential applicability to treatment of brain tumors

Hypothalamic growth hormone (GH)-releasing hormone (GHRH) stimulates the synthesis and release of GH from the pituitary gland. GHRH and its mRNA are also found in human cancers of the breast, ovary, prostate, lung, and other tumors, suggesting that GHRH is also a tumor growth factor. Various studies show that GHRH antagonists have antiproliferative effects in many tumor models; however, glioblastomas were examined only recently. Previous studies have demonstrated that s.c. administration of GHRH antagonist (JV-1-36) inhibited growth of s.c. U-87MG human glioblastomas and increased survival of nude mice with orthotopic implants of glioblastomas. Although treatment with JV-1-36 reduced tumorigenicity, it is not known whether peripherally administered GHRH antagonists can cross the blood-brain barrier. Brain endothelial cells joined by tight junctions form the blood-brain barrier, a "barrier" between the general circulation and the CNS. In this study, we administered a GHRH antagonist (JV-1-42) and showed that, after i.v. injection, iodinated JV-1-42 (131I-JV-1-42) enters the brain intact at a rate of 0.8514 mocrol/g per min with a serum half-life of 12.2 min. A one-site binding hyperbolic model indicated that the maximal percent of i.v. dose taken up per gram of brain was 0.41%. Coinjection of unlabeled JV-1-42 indicated that the transport from blood to brain is not saturable; however, transport from brain to blood is saturable and involves P-glycoprotein. Taken together, these results demonstrate that i.v.-administered 131I-JV-1-42 readily crosses the blood-brain barrier and accumulates in the brain. This finding indicates that GHRH antagonists could provide a potential treatment for malignant glioblastomas.

Antagonists of growth hormone releasing hormone (GHRH) and of bombesin/gastrin releasing peptide (BN/GRP) suppress the expression of VEGF, bFGF, and receptors of the EGF/HER family in PC-3 and DU-145 human androgen-independent prostate cancers

BACKGROUND

Antagonists of growth hormone releasing hormone (GHRH) as well as antagonists of bombesin/gastrin releasing peptide (BN/GRP) inhibit the growth of various malignancies (cancers) including prostate cancer.

METHODS

We investigated the effects of GHRH antagonists MZ-J-7-118 and RC-J-29-18, BN/GRP antagonists RC-3940-II and RC-3940-Et and the combination of MZ-J-7-118 and RC-3940-II on the growth of PC-3 and DU-145 human androgen independent prostate cancers xenografted s.c. into nude mice. To elucidate the mechanisms of action of these analogs, growth factors like IGF-II (insulin-like growth factor-II), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and epidermal growth factor receptor/human epidermal growth factor receptor (EGF-R/HER) family were measured in tumors as well as IGF-I in serum.

RESULTS

Antagonists of GHRH and BN/GRP alone or in combination significantly inhibited growth of PC-3 and DU-145 tumors, the greatest inhibition of tumor volume being achieved by combination of MZ-J-7-118 (5 microg/day) and RC-3940-II (10 microg/day). BN/GRP and GHRH antagonists and their combination also decreased the expression of VEGF significantly in PC-3 and non-significantly in DU-145, as measured by radioimmunoassay for VEGF protein and RT-PCR for mRNA levels of VEGF. GHRH and BN/GRP antagonists reduced bFGF concentrations and the maximal binding capacity of EGF receptors, and their mRNA levels in PC-3 and DU-145 tumors. mRNA levels for HER-2 and -3 were also diminished in PC-3 tumors by GHRH and BN/GRP antagonists. No changes in HER-4 were found after treatment. Serum IGF-I and tumoral IGF-II levels were not affected by the analogs.

CONCLUSIONS

BN/GRP and GHRH antagonists inhibit growth of PC-3 and DU-145 prostate cancers by suppressing the expression of tumoral growth factors such as VEGF and bFGF as well as the receptors for EGF and related HER-2 and -3. Additive effects on tumor inhibition (TI) in vivo, but not on VEGF, bFGF, or members of the EGF/HER receptor family, can be achieved by the joint administration of both classes of analogs.

Effective treatment of experimental human non-Hodgkin's lymphomas with antagonists of growth hormone-releasing hormone

Antagonists of growth hormone-releasing hormone (GHRH) were shown to inhibit the growth of various cancers. We investigated the antitumor activity and the mechanism of action of GHRH antagonists in human non-Hodgkin's lymphomas (NHL). Nude mice bearing xenografts of RL and HT human NHL were treated with GHRH antagonists MZ-5-156 and MZ-J-7-138 at a dose of 40 microg twice daily. The concentrations of serum IGF-1 and GHRH, bFGF, and VEGF in tumor tissue were measured by radioimmunoassays. Expression of GHRH and splice variant 1 of the GHRH receptor in both cell lines was examined by RT-PCR. The effects of MZ-5-156, MZ-J-7-138 and GHRH on cell proliferation were evaluated in vitro. Treatment with MZ-5-156 and MZ-J-7-138 significantly (P < 0.05) inhibited the growth of RL and HT tumors by 59.9-73.9%. High-affinity binding sites for GHRH and mRNA for GHRH and splice variant-1 of the GHRH receptors were found on RL and HT tumors. RL and HT cells contained GHRH peptide, and their growth in vitro was significantly inhibited by both antagonists. IGF-I levels in serum of mice were significantly decreased by antagonist MZ-5-156. Therapy with GHRH antagonists also significantly reduced tumoral bFGF, whereas VEGF levels were not suppressed. Our findings suggest that GHRH antagonists inhibit the growth of RL and HT lymphomas by direct effects mediated by tumoral receptors for GHRH. GHRH antagonists could offer a new therapeutic modality for the management of advanced NHL.

Expression of growth hormone-releasing hormone receptor splicing variants in human primary adrenocortical tumours

OBJECTIVE

Several splice variants (SVs) of GHRH receptor (GHRH-R) have been identified in various human cancers through which GHRH antagonists may exert their IGF-II-mediated antiproliferative action. Because the overexpression of the IGF-II gene is a frequent feature of adrenal carcinoma, we searched for the presence of GHRH-R SVs in these tumours.

METHODS AND RESULTS

The expression of GHRH-R SVs was assessed by nested PCR in 45 human adrenocortical tumours. We have amplified 720-, 566- and 335-bp PCR products only in carcinomas. Their sequence revealed three open reading frames, corresponding to SV1, SV2 and SV4 of GHRH-R. SV2 was detected in five of 24 cancers examined, whereas the incidence of SV1 and SV4 was lower. Their simultaneous expression was observed in one carcinoma. No PCR products for SV3 or wild-type GHRH-R were found in carcinomas; mRNA for wild-type GHRH-R or SVs of GHRH-R were not observed either in adenomas or in normal adrenal or in NCI-H295R cells. Interestingly, all carcinomas which expressed SVs were also positive for the presence of GHRH mRNA.

CONCLUSION

This is the first time that the expression of splice variants of GHRH-R has been demonstrated in human adrenal carcinoma. This study raises the possibility that splice variants might play a role in adrenal carcinogenesis and might offer the possibility for new therapeutic strategies at least in a subgroup of adrenal carcinomas.

Antagonist of growth hormone-releasing hormone induces apoptosis in LNCaP human prostate cancer cells through a Ca2+-dependent pathway

Antagonists of growth hormone-releasing hormone (GHRH) exert antiproliferative effects directly on cancer cells, which are mediated by the tumoral GHRH receptors. However, the signal transduction pathways involved in antiproliferative effect of GHRH antagonists have not yet been elucidated. We used flow cytometry to investigate whether GHRH antagonist JV-1-38 can induce changes in the cytosolic free Ca2+ concentration leading to apoptosis in LNCaP human prostate cancer cells. JV-1-38 evoked prompt Ca2+ signal in a dose-dependent way (1-10 microM) and induced early stage of apoptosis in LNCaP human prostate cancer cells at a concentration effective in suppression of cell proliferation (10 microM) peaking after 3 h. Unexpectedly, agonist GHRH(1-29)NH2, which elevates cytosolic free Ca2+ concentration in pituitary somatotrophs at nanomolar concentrations, failed to induce Ca2+ signal or apoptosis even at a 10-fold higher concentration (100 microM). However, agonist GHRH(1-29)NH2 inhibited JV-1-38-induced Ca2+ signals in a dose-dependent way without affecting the antagonist-induced apoptosis. Peptides unrelated to GHRH did not induce Ca2+ signals in LNCaP human prostate cancer cells. EDTA (10 mM) or nifedipine (10 microM) significantly reduced the Ca2+ signal and early stage of apoptosis induced by JV-1-38, supporting the view that the increase in intracellular Ca2+ in response to JV-1-38 occurs primarily through extracellular Ca2+ entry through voltage-operated Ca2+ channels. In conclusion, GHRH antagonists activate tumoral GHRH receptors and are able to induce apoptosis in LNCaP human prostate cancer cells through a Ca2+-dependent pathway. Treatment with GHRH antagonists may offer a new approach to the therapy of prostate and other hormone-sensitive cancers.

Extrapituitary Effects of the Growth Hormone-Releasing Hormone

Growth hormone-releasing hormone (GHRH) is a neuropeptide secreted by the hypothalamus that stimulates the synthesis and release of growth hormone (GH) in the pituitary. Accumulating evidence suggests that in addition to GHRH's neuroendocrine action, GHRH is present in several extrahypothalamic tissues and is involved in a variety of cellular processes. Its function is related to the regulation of cell proliferation and differentiation of various nonpituitary cell types. In certain cases, ectopic production of GHRH has also been implicated in carcinogenesis. The mechanisms by which GHRH affects the peripheral extrapituitary tissues remain poorly understood, but it is likely that classic neuroendocrine action as well as paracrine and autocrine pathways are involved. Some headway has been made in the identification of extrapituitary receptors for GHRH and cDNA as splice variants of these GHRH receptors found in various tumors. The fact that the nonpituitary GHRH receptors are not fully identified, however, remains the major obstacle in studying, at a more mechanistic level, the action of local GHRH. This review summarizes the information available regarding the role of GHRH in the extrapituitary tissues with emphasis on its potential therapeutic and diagnostic applications.

Inhibitory Effect of Antagonists of Bombesin and Growth Hormone-Releasing Hormone on Orthotopic and Intraosseous Growth and Invasiveness of PC-3 Human Prostate Cancer in Nude Mice

Purpose: To determine whether antagonists of growth hormone-releasing hormone (GHRH) and bombesin/gastrin-releasing peptide (BN/GRP) can inhibit the orthotopic and metastatic growth of PC-3 human androgen-independent prostate cancers.

Experimental Design: The effects of administration of GHRH antagonist MZ-J-7-118, BN/GRP antagonist RC-3940-II, and their combination on the growth and metastatic spread of PC-3 tumors implanted orthotopically into nude mice were evaluated. The efficacy of this treatment on PC-3 tumors implanted intratibially and s.c. was also determined.

Results: Treatment with MZ-J-7-118, RC-3940-II, or their combination significantly inhibited the growth of PC-3 tumors implanted orthotopically, intraosseously, and s.c. The combination of the two antagonists had the greatest effect, inhibiting orthotopic tumor growth by 77%, intratibially implanted tumors by 86%, and s.c. tumors by 86%. The therapy with BN/GRP and GHRH antagonists, especially in combination, also reduced the local tumor spread and distant metastases in animals bearing orthotopic tumors. Combination therapy was likewise the most effective in reducing the incidence and severity of tibial osteolytic lesions and pathologic fractures in intraosseously implanted tumors. High-affinity binding sites for BN/GRP and GHRH were found in s.c. and orthotopic PC-3 tumor samples. MZ-J-7-118, RC-3940-II, and the combination of both compounds inhibited in vitro growth of PC-3 cells.

Conclusions: Our findings show the efficacy of BN/GRP antagonists and GHRH antagonists for the treatment of advanced prostate cancer in preclinical metastatic models. As BN/GRP antagonists are already in clinical trials and GHRH antagonists are effective in androgen-independent prostate cancer models, these analogues could be considered for the management of advanced prostate carcinoma.

Effect of gsp oncogene on somatostatin receptor subtype 1 and 2 mRNA levels in GHRH-responsive GH3 cells

Growth hormone releasing hormone (GHRH) signals via G protein-coupled receptors (GHRH-R) to enhance intracellular Galphas/adenylyl cyclase/cAMP signaling, which in turn has positive effects on GH synthesis and release, as well as proliferation of the GH-producing cells of the anterior pituitary gland. Some GH-producing pituitary tumors express a constitutively active mutant form of Galphas (gsp oncogene). It has been reported that these tumors are more responsive to octreotide therapy. In this study we used a rat GH-producing cell line (GH3) stably transfected with the human GHRH-R cDNA (GH3-GHRHR cells) as a model to study the effects of gsp oncogene on somatostatin (SRIH) receptor subtype 1 and 2 (sst1 and sst2) mRNA levels. Transient transfection of gsp oncogene in GH3-GHRHR cells for 48 h increased intracellular cAMP levels and GH release. Phosphodiesterase (PDE) 4, sst1 and sst2 mRNA levels were increased by G protein mutation as assessed by real-time RT-PCR. Increased PDE mRNA levels in gsp-transfected cells may be a compensatory mechanism to the constitutive activation of cAMP-dependent pathway by G protein mutation and is consistent with reports of higher PDE expression in human pituitary tumor that express gsp. Our data suggest that higher expression of sst1 and sst2 mRNA induced by the gsp oncogene may be a mechanism by which gsp-positive tumors show a greater response to SRIH. GH3 cells permanently transfected with GHRH-R can be used for in vitro studies of actions of GHRH.

Altered messenger RNA and protein expressions for insulin-like growth factor family members in clear cell and papillary renal cell carcinomas

BACKGROUND

The purpose of the present paper was to describe the pattern of expression of insulin-like growth factor (IGF-I) and its regulatory binding proteins (IGFBP) in renal cell carcinoma (RCC).

METHODS

The expressions of mRNA and protein for various IGF members were assessed in 24 paired normal and malignant human renal tissues (16 clear cell and 8 papillary RCC) using semiquantitative reverse transcription-polymerase chain reaction and immunohistochemistry. Paired tissue samples were also obtained from six patients with oncocytoma in order to compare the specificity of changes in IGF/IGFBP expression between tumors derived from proximal (RCC) and distal (oncocytoma) tubular epithelium.

RESULTS

Clear cell RCC were characterized by significant increases in the mRNA expression of IGF-I, IGFBP-3 and IGFBP-6 while papillary RCC exhibited down-regulated expression of IGF-I, IGFBP-4 and IGFBP-5. The IGFBP-2, IGFBP-4 and IGFBP-5 mRNA were down-regulated in oncocytomas. Semiquantitative assessment of immunohistochemical staining demonstrated significant increases in epithelial associated IGF-I and IGFBP-3 in clear cell RCC, increased IGFBP-5 protein in papillary RCC and no significant changes in IGF/IGFBP protein expression in oncocytoma.

CONCLUSIONS

The expression of IGF-I and certain IGFBP is significantly altered in RCC compared with normal renal tissue and oncocytomas. This altered expression is differentially regulated according to the histologic subtype of RCC, and suggests that the IGF/IGFBP axis may play an important role in determining the malignant phenotype of RCC.

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of various human cancers by multiple mechanisms, which include direct effects on tumor cells through the splice variants (SV) of the GHRH receptor. Our findings suggest that the tumoral protein encoded by SV 1 (SV1) is a likely functional receptor. The aim of this study was to develop a polyclonal antiserum against a polypeptide analog of segment 1-25 of the putative SV1 receptor protein. Rabbits were immunized with [Ala-23]SV1 (1-25)-Tyr-26-Cys-27-NH2 as a hapten, conjugated to BSA or keyhole limpet hemocyanin. The antisera thus generated were evaluated by RIA for binding to the radiolabeled hapten. The specificity and sensitivity of the antisera were studied on xenografts of RL and HT human non-Hodgkin's lymphomas. The sera raised against keyhole limpet hemocyanin-SV1 hapten, showed binding values of 50-75% at a 1:56,000 dilution. In Western blot analyses, the purified polyclonal antibody recognized a specific signal with a molecular mass of approximately 40 kDa in RL and HT lymphomas. This band corresponds to the estimated molecular mass of the GHRH receptor isoform encoded by SV1. RT-PCR and ligand binding studies also revealed the expression of SV1 and the presence of high-affinity binding sites for GHRH on RL and HT tumors. Because the antiserum developed recognizes the tumoral GHRH receptor protein encoded by SV1, it should be of value in various investigations.

Increased activity of antagonists of growth hormone-releasing hormone substituted at positions 8, 9, and 10

Antagonists of human growth hormone-releasing hormone (hGHRH) with increased potency and improved enzymatic and chemical stability are needed for potential clinical applications. We synthesized 21 antagonistic analogs of hGHRH(1-29)NH(2), substituted at positions 8, 9, and 10 of the common core sequence [phenylacetyl-Tyr(1), d-Arg(2,28), para-chloro-phenylalanine 6, Arg(9)/homoarginine 9, Tyr(10)/O-methyltyrosine 10, alpha-aminobutyric acid 15, norleucine 27, Har(29)] hGHRH(1-29)NH(2). Inhibitory effects on hGHRH-induced GH release were evaluated in vitro in a superfused rat pituitary system, as well as in vivo after i.v. injection into rats. The binding affinities of the peptides to pituitary GHRH receptors were also determined. Introduction of para-amidinophenylalanine 10 yielded antagonists JV-1-62 and -63 with the highest activities in vitro and lowest receptor dissociation constants (K(i) = 0.057-0.062 nM). Antagonists JV-1-62 and -63 also exhibited the strongest effect in vivo, significantly (P < 0.05-0.001) inhibiting hGHRH-induced GH release for at least 1 h. Para-aminophenylalanine 10 and O-ethyltyrosine 10 substitutions yielded antagonists potent in vitro, but His(10), 3,3'-diphenylalanine 10, 2-naphthylalanine 10, and cyclohexylalanine 10 modifications were detrimental. Antagonists containing citrulline 9 (in MZ-J-7-72), amidinophenylalanine 9 (in JV-1-65), His(9), d-Arg(9), citrulline 8, Ala(8), d-Ala(8), or alpha-aminobutyric acid 8 substituents also had high activity and receptor affinity in vitro. However, in vitro potencies of analogs with substitution in position 9 correlated poorly with acute endocrine effects in vivo, as exemplified by the weak and/or short inhibitory actions of antagonists JV-1-65 and MZ-J-7-72 on GH release in vivo. Nevertheless, antagonist JV-1-65 was more potent than JV-1-63 in tests on inhibition of the growth of human prostatic and lung cancer lines xenografted into nude mice. This indicates that oncological activity may be based on several mechanisms. hGHRH antagonists with improved efficacy could be useful for treatment of cancers that depend on insulin-like growth factors or GHRH.

Inhibition of mutant p53 expression and growth of DMS-153 small cell lung carcinoma by antagonists of growth hormone-releasing hormone and bombesin

We investigated the effects of growth hormone-releasing hormone (GHRH) antagonists, JV-1-65 and JV-1-63, and bombesin/gastrin-releasing peptide (BN/GRP) antagonist RC-3940-II on DMS-153 human small cell lung carcinoma xenografted into nude mice. Treatment with 10 microg/day JV-1-65 or RC-3940-II decreased tumor volume by 28% (P < 0.05) and 77% (P < 0.01), respectively, after 42 days compared with controls. Combination of JV-1-65 and RC-3940-II induced the greatest inhibition of tumor proliferation (95%; P < 0.01), suggesting a synergism. Western blotting showed that the antitumor effects of these antagonists were associated with inhibition of the expression of the mutant tumor suppressor protein p53 (Tp53). Mutation was detected by sequence analysis of the p53 gene at codon 155: ACC [Thr] --> CCC [Pro]. Combination of JV-1-65 and RC-3940-II decreased the levels of mutant p53 protein by 42% (P < 0.01) compared with controls. JV-1-65, JV-1-63, and RC-3940-II, given singly, reduced mutant p53 protein expression by 18-24% (P < 0.05). Serum insulin-like growth factor (IGF)-I levels were diminished in animals receiving GHRH antagonists. mRNA levels for IGF-II, IGF receptor-I, GRP receptor, and EGF receptor in tumors were significantly decreased by combined treatment with JV-1-65 and RC-3940-II. DMS-153 tumors expressed mRNAs for GHRH and GHRH receptor splice variants 1 and 2, suggesting that GHRH could be an autocrine growth factor. Proliferation of DMS-153 cells in vitro was stimulated by GRP and IGF-II and inhibited by JV-1-65. This study indicates that GHRH antagonists and BN/GRP antagonist inhibit the growth of DMS-153 small cell lung carcinoma concomitantly with the expression of mutant Tp53, which might uncouple the signal transduction pathways for cell growth stimulation.

Ligand-dependent and -independent effects of splice variant 1 of growth hormone-releasing hormone receptor

Existing evidence indicates that, in addition to its neuroendocrine action, growth hormone-releasing hormone (GHRH) acts directly on several nonpituitary tissues, especially neoplasms, and stimulates cell proliferation. We have recently reported that a splice variant of the receptor (SV1) is expressed in various normal tissues and particularly in tumor tissues, producing mitogenic effects on GHRH binding. By using HEC-1A human endometrial carcinoma cells, which express endogenous SV1, we show that, in addition to its ability to mediate the mitogenic effects of GHRH, SV1 also possesses relatively high intrinsic, ligand-independent activity. By using an antisense RNA-based approach we found that SV1 ablation reduces the efficacy of colony formation and the rate of cell proliferation of HEC-1A cells in the absence of exogenous GHRH, and decreases their sensitivity to GHRH when the neurohormone is added to the culture media. This ligand-independent stimulation of cell proliferation appears to be a characteristic property of the truncated form of the receptor, because the expression of SV1 and not of the full-length GHRH receptor stimulated the proliferation of 3T3 fibroblasts in the absence of exogenous GHRH, whereas both forms mediated the proliferative effects of GHRH. Evaluation of 21 specimens of human primary endometrial carcinoma for expression of SV1 by immunohistochemistry indicated that in contrast to the GHRH receptor, which is absent, SV1 is expressed in approximately 43% of the specimens. These findings indicate that SV1 can operate in a ligand-independent as well as a ligand-dependent manner. The overexpression of this form of GHRH receptor may be associated with carcinogenesis.

Growth hormone-releasing hormone and extra-pituitary tumorigenesis: therapeutic and diagnostic applications of growth hormone-releasing hormone antagonists

Growth hormone-releasing hormone (GHRH) regulates growth hormone release from the pituitary. However, in addition to this neuroendocrine action, much evidence implies an additional role for GHRH in carcinogenesis in non-pituitary tissues. This role of GHRH in cancer development appears to be due to the operation of several mechanisms, which involve the regulation of the growth hormone-dependent hepatic insulin-like growth factor I (IGFI) production, tumoural IGF-I and IGF-II secretion and direct action of GHRH on tumour cells by autocrine and/or paracrine pathways. This review summarises the available information regarding the role of GHRH in tumorigenesis with special emphasis on the direct action of GHRH in primary and experimental cancers.

GH-RH antagonist (MZ-4-71) inhibits VEGF secretion and proliferation of murine endothelial cells

Angiogenesis plays a key role in solid tumor formation, invasiveness and metastasis. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen that is necessary in the process of neovascularisation. Antagonists of growth hormone-releasing hormone (GH-RH) have been shown to suppress both in vivo and in vitro growth and metastasis of many human cancer cell lines. The mechanisms that mediate the antitumorigenic actions of these antagonists involve direct and indirect pathways, but are not completely elucidated. We have examined the effect of GH-RH antagonist MZ-4-71 on proliferation activity and VEGF release from cultured murine endothelial cells HECa10 in vitro. MZ-4-71 at 10(-8) to 10(-6) M concentrations inhibited the proliferative activity of cultured cells and suppressed the release of VEGF into supernatants of 72 h endothelial cell cultures. To our knowledge this is the first study reporting antiangiogenic properties of GH-RH antagonists.

The expression of growth hormone-releasing hormone (GHRH) and its receptor splice variants in human breast cancer lines; the evaluation of signaling mechanisms in the stimulation of cell proliferation

Antagonists of growth hormone-releasing hormone (GHRH) inhibit growth of various human cancers including breast cancer, xenografted into nude mice or cultured in vitro. Splice variants (SVs) of receptors for GHRH have been found in several human cancers and cancer cell lines. The antiproliferative actions of GHRH antagonists could be mediated in part through these SVs of GHRH receptors. In this study we examined the expression of mRNA for GHRH and SVs of its receptors in human breast cancer cell lines MCF-7, MCF-7MIII, MDA-MB-231, MDA-MB-435, MDA-MB-468, and T47D. mRNA for GHRH was present in all lines tested. mRNA for SV1 isoform of GHRH receptors was found in MCF-7MIII, MDA-MB-468, and T47D; and for SV2 isoform in MCF-7MIII and T47D cell lines. In proliferation studies in vitro, the growth of T47D cells was stimulated by GHRH and dose-dependently inhibited by GHRH antagonist JV-1-38. H89 (protein kinase A inhibitor), bisindolylmaleimide I (protein kinase C [PKC] inhibitor) and verapamil (voltage-dependent calcium channel blocker) inhibited the GHRH-stimulated proliferation of T47D cells. The GHRH antagonist JV-1-38 suppressed the T47D cell growth in vitro stimulated by PKC activator (phorbol-12-myristate-13-acetate). The stimulation of T47D cells by GHRH was followed by an increase in cAMP production and GHRH antagonist JV-1-38 competitively inhibited this effect. Our results suggest that SVs of GHRH receptors could mediate the responses to GHRH and GHRH antagonists in breast cancer through Ca2+-, cAMP- and PKC-dependent mechanisms. The presence of SV1 of GHRH receptors in human cancers provides a rationale for antitumor therapy based on the blockade of this receptor by specific GHRH antagonists.

Expression of mRNA for growth hormone-releasing hormone and splice variants of GHRH receptors in human malignant bone tumors

Splice variants (SV) of receptors for growth hormone-releasing hormone (GHRH) have been found in several human cancer cell lines. GHRH antagonists inhibit growth of various human cancers, including osteosarcomas and Ewing's sarcoma, xenografted into nude mice or cultured in vitro and their antiproliferative action could be mediated, in part, through these SV of GHRH receptors. In this study, we found mRNA for the SV(1) isoform of GHRH receptors in human osteosarcoma line MNNG/HOS and SK-ES-1 Ewing's sarcoma line. We also detected mRNA for GHRH, which is apparently translated into the GHRH peptide and secreted by the cells, as shown by the presence of GHRH-like immunoreactivity in the conditioned media of cell cultures. In proliferation studies in vitro, the growth of SK-ES-1 and MNNG/HOS cells was dose-dependently inhibited by GHRH antagonist JV-1-38 and an antiserum against human GHRH. Our study indicates the presence of an autocrine stimulatory loop based on GHRH and SV(1) of GHRH receptors in human sarcomas. The direct antiproliferative effects of GHRH antagonists on malignant bone tumors appear to be exerted through the SV(1) of GHRH receptors on tumoral cells.

Inhibition of proliferation in human MNNG/HOS osteosarcoma and SK-ES-1 Ewing sarcoma cell lines in vitro and in vivo by antagonists of growth hormone-releasing hormone: effects on insulin-like growth factor II

BACKGROUND

Antagonists of growth hormone-releasing hormone (GH-RH) can inhibit the proliferation of various tumors either indirectly through the suppression of the pituitary growth hormone/hepatic insulin-like growth factor I (IGF-I) axis and the lowering of serum IGF-I concentration or directly by reducing the levels of IGF-I and IGF-II and their mRNA expression in tumors and blocking the effect of autocrine GH-RH. In this study, the authors investigated the effects of the GH-RH antagonist JV-1-38 on MNNG/HOS human osteosarcoma and SK-ES-1 human Ewing sarcoma cell lines.

METHODS

Male nude mice bearing subcutaneous xenografts of MNNG/HOS or SK-ES-1 tumors were treated subcutaneously with JV-1-38 at a dose of 20 microg twice daily for 4 weeks. The concentrations of IGF-I and IGF-II in serum and in tumor tissue were measured by radioimmunoassay. Tumor and liver levels of mRNA for IGF-I and IGF-II were determined by reverse transcriptase-polymerase chain reaction analysis. The effects of JV-1-38, IGF-I, and IGF-II on cell proliferation in vitro were evaluated.

RESULTS

GH-RH antagonist significantly (P < 0.05) inhibited the tumor volume and tumor weight of MNNG/HOS and SK-ES-1 tumors by > 50% after 4 weeks and increased tumor doubling time. JV-1-38 lowered the serum IGF-I level, decreased the expression of mRNA for IGF-I in the liver, and significantly (P < 0.05-0.01) reduced the concentration of IGF-II and mRNA levels for IGF-II in both sarcomas. The concentration of IGF-I was lowered only in SK-ES-1 tumors. In vitro, the proliferation of SK-ES-1 and MNNG/HOS cells was inhibited by JV-1-38 and by antisera to IGF-I and IGF-II.

CONCLUSIONS

The inhibition of MNNG/HOS osteosarcoma and SK-ES-1 Ewing sarcoma by GH-RH antagonists was linked to a suppression of IGF-II production in tumors. However, in SK-ES-1 tumors, the effects on IGF-I also may be involved.

The expression of growth hormone-releasing hormone (GHRH) and splice variants of its receptor in human gastroenteropancreatic carcinomas

Splice variants (SVs) of receptors for growth hormone-releasing hormone (GHRH) have been found in primary human prostate cancers and diverse human cancer cell lines. GHRH antagonists inhibit growth of various experimental human cancers, including pancreatic and colorectal, xenografted into nude mice or cultured in vitro, and their antiproliferative action could be mediated in part through SVs of GHRH receptors. In this study we examined the expression of mRNA for GHRH and for SVs of its receptors in tumors of human pancreatic, colorectal, and gastric cancer cell lines grown in nude mice. mRNA for both GHRH and SV(1) isoform of GHRH receptors was expressed in tumors of pancreatic (SW1990, PANC-1, MIA PaCa-2, Capan-1, Capan-2, and CFPAC1), colonic (COLO 320DM and HT-29), and gastric (NCI-N87, HS746T, and AGS) cancer cell lines; mRNA for SV(2) was also present in Capan-1, Capan-2, CFPAC1, HT-29, and NCI-N87 tumors. In proliferation studies in vitro, the growth of pancreatic, colonic, and gastric cancer cells was stimulated by GHRH(1-29)NH(2) and inhibited by GHRH antagonist JV-1-38. The stimulation of some gastroenteropancreatic cancer cells by GHRH was followed by an increase in cAMP production, and GHRH antagonist JV-1-38 competitively inhibited this effect. Our study indicates the presence of an autocrine/paracrine stimulatory loop based on GHRH and SV(1) of GHRH receptors in human pancreatic, colorectal, and gastric cancers. The finding of SV(1) receptor in human cancers provides an approach to an antitumor therapy based on the blockade of this receptor by specific GHRH antagonists.

Sleep loss alters hypothalamic growth hormone-releasing hormone receptors in rats

Previous experiments suggest that sleep deprivation (SD) is associated with growth hormone-releasing hormone (GHRH) release and that GHRH promotes sleep via intrahypothalamic sites of action. Binding of [His(1), (125)I-Tyr(10), Nle(27)]hGHRH(1-32) amide and GHRH receptor (GHRH-R) mRNA levels were determined in the hypothalamus and pituitary of rats subjected to 8 h of SD and of undisturbed control rats. The characteristics of the hypothalamic GHRH binding sites differed from those of the pituitary. High affinity GHRH binding and GHRH-R mRNA levels decreased by 50% in the hypothalamus of SD rats, whereas there were no alterations in the pituitary. The results demonstrate that GHRH-Rs exist in the hypothalamus and they respond differently to SD than the GHRH-Rs in the pituitary. The SD-induced changes are explained by down-regulation of the hypothalamic GHRH-Rs induced by GHRH release during and after SD.

Inhibition of proliferation of PC-3 human prostate cancer by antagonists of growth hormone-releasing hormone: lack of correlation with the levels of serum IGF-I and expression of tumoral IGF-II and vascular endothelial growth factor

BACKGROUND

Antagonists of growth hormone-releasing hormone (GHRH) such as JV-1-38 can inhibit androgen-independent prostate cancer directly by several mechanisms and/or indirectly by suppressing growth hormone/insulin-like growth factor-I (GH/IGF-I) axis. To shed more light on the mechanisms involved, the effects of JV-1-38 on PC-3 human prostate cancer were compared with those of somatostatin analog RC-160 in vivo and in vitro.

METHODS

Nude mice bearing PC-3 tumors received JV-1-38 (20 microg), RC-160 (50 microg) or a combination of JV-1-38 and RC-160. The concentration of IGF-I in serum and the expression of mRNA for IGF-II and vascular endothelial growth factor (VEGF) in tumor tissue were investigated.

RESULTS

In vivo, the final volume of PC-3 tumors treated with JV-1-38 was significantly lowered by 49% (P < 0.01), whereas RC-160 exerted only 30% inhibition (NS), compared with controls. Combined use of both compounds augmented tumor inhibition to 63% (P < 0.001). Serum IGF-I levels were decreased only in mice treated with RC-160. JV-1-38 suppressed mRNA for IGF-II in PC-3 tumors by 42%, whereas RC-160 alone or in combination with JV-1-38 caused a 65% reduction. JV-1-38 and RC-160 used as single drugs decreased the expression of VEGF by 50%, and their combination caused a 63% reduction. In vitro, JV-1-38 inhibited the proliferation of PC-3 cells by 39%. This effect could be partially reversed by addition of IGF-I to the serum-free medium. RC-160 alone did not affect the PC-3 cell growth in vitro, but in combination with JV-1-38 it augmented the antiproliferative effect of the GH-RH antagonist to 72%. Exposure to JV-1-38 in vitro reduced the expression of mRNA for IGF-II in PC-3 cells by 55% but did not change VEGF mRNA levels, whereas RC-160 had no effect.

CONCLUSIONS

The antiproliferative effect of JV-1-38 was not associated with the suppression of serum IGF-I and was only partially correlated with the expression of IGF-II and VEGF in PC-3 tumors, suggesting that other mechanisms play a role in the antitumor action of GHRH antagonists. Nevertheless, the stronger inhibition of tumor growth after combined treatment with JV-1-38 and RC-160 indicates that the interference with multiple local stimulatory factors leads to an enhanced inhibition of prostate cancer.

Characterization of a growth hormone-releasing hormone binding site in the rat renal medulla

Receptor binding analysis was performed in the renal medulla from 2-month-old rats, an extrapituitary tissue containing the highest level of GHRH receptor mRNA. At 4 degrees C, in the presence of a cocktail of protease inhibitors, binding of [125I-Tyr(10)]hGHRH (1-44)NH(2) to medullary homogenates was specific, time-dependent, reversible and saturable (K(d): 28 nM; B(max): 30 fmol/mgprot.). In these experimental conditions, no change of binding parameters could be detected in the course of aging. The structure-affinity profile was different in the two tissues and chemical cross-linking revealed the presence of 65-, 55- and 38-kDa 125I-GHRH-labeled complexes in the renal medulla compared to 65-, 47- and 28-kDa radioactive complexes in the anterior pituitary. It is suggested that GHRH binding sites, and possibly the receptor, may be different in the two tissues.