Growth Hormone-releasing Hormone Antagonists Research Articles

Treatment of urinary bladder cancers by growth hormone-releasing hormone antagonists: A preclinical report.

433 Background: Urinary bladder cancer is the fifth most frequent cancer diagnosed and among the most expensive cancers to treat in the United States. The management of muscle-invasive tumors presents a clinical challenge because of the toxicity and limitations in efficacy and durability of current therapeutic modalities. Novel therapeutic strategies for this disease are of paramount importance. Growth hormone-releasing hormone (GHRH) receptors and its splice variant were detected in a series of urothelial malignancies and GHRH has been shown to influence the growth of these tumors. Herein we evaluated the effect of GHRH antagonists on the growth of various experimental human urinary bladder cancers in vitro and in vivo in nude mice. Methods: We investigated the effects of several GHRH antagonists MIA 602, MIA 606 and MIA 690 on growth of urothelial HT-1376, J82, and RT-4 tumors xenografted into nude mice. The presence of GHRH receptors was validated by Western blotting. Results: The receptors for GHRH and their main splice variant, SV1, were detected in tumor samples of all 3 human bladder cancer models. In the HT-1376 tumors, the GHRH antagonists caused a 30-60% reduction in volume and 52-70% decrease in tumor weights (p < 0.05). All three antagonists strongly inhibited growth of J82 cancers as shown by a 62-75% reduction in tumor volume and 54-66% decrease in tumor weights (p < 0.05). Treatment with MIA-602 and MIA-606 resulted in a similar marked inhibition of growth of RT-4 cancers; tumor volume and weights were reduced by about 51-71% in the treated groups (p < 0.05). The mice tolerated this therapy well; body and organ weights were not significantly changed by the treatments. No toxicity from the GHRH antagonists was noted. Conclusions: We demonstrated the efficacy of potent GHRH antagonists and their lack of toxicity in inhibiting the growth of experimental models of bladder cancer in vivo. The expression of GHRH receptors was detected in all 3 models of human primary urothelial bladder carcinomas. Our findings warrant further development of GHRH antagonists for clinical therapy of bladder cancer alone or in combination with current chemotherapeutic agents and Exploration of their mechanism of action.

Expression of Receptors for Pituitary-Type Growth Hormone-Releasing Hormone (pGHRH-R) in Human Papillary Thyroid Cancer Cells: Effects of GHRH Antagonists on Matrix Metalloproteinase-2.

Papillary thyroid cancer (PTC) is the most prevalent of all endocrine cancers. In recent studies, the presence of receptors for pituitary-type growth hormone-releasing hormone (pGHRH-R) has been demonstrated in various human cancers, including human prostate, brain, and other cancer lines. Thyroid malignancies, however, have not yet been investigated in this regard. In this study, we found that pGHRH-R and its functional splice variant, SV1, are present in normal thyroid and PTC cells. We also treated seven normal and PTC tumor thyroid cells in vitro with a GHRH antagonist, MIA-602, to compare its anti-proliferation and anti-invasion potential against vehicle-treated cells. We found that treatment with GHRH antagonist increases the expression of SV1 and pGHRH-R in tumor cells compared to tumor cells exposed to vehicle only, a response which may alter the sensitivity of signaling kinases within the cells. GHRH antagonist treatment of tumor cells also reduced activity of the tumor invasion marker, matrix metalloproteinase (MMP)-2, compared to tumor cells exposed to vehicle only. The expression of pGHRH-R and SV1, as well as MMP-2 activity, in normal thyroid cells remained unaffected by GHRH antagonist treatment. Similarly, cell proliferation rates for tumor or normal thyroid cells were not affected by GHRH antagonist treatment. Our findings have important implications for the therapeutic use of GHRH antagonist in cases of aggressive PTC refractory to conventional treatment modalities, and in which protein expression and MMP-2 activity in normal thyroid tissue is left unaltered.

Antagonistic analogs of growth hormone-releasing hormone increase the efficacy of treatment of triple negative breast cancer in nude mice with doxorubicin; A preclinical study.

This study evaluated the effects of an antagonistic analog of growth hormone-releasing hormone, MIA-602, on tumor growth, response to doxorubicin, expression of drug resistance genes, and efflux pump function in human triple negative breast cancers. HCC1806 (doxorubicin-sensitive) and MX-1 (doxorubicin-resistant), cell lines were xenografted into nude mice and treated with MIA-602, doxorubicin, or their combination. Tumors were evaluated for changes in volume and the expression of the drug resistance genes MDR1 and NANOG. In-vitro cell culture assays were used to analyze the effect of MIA-602 on efflux pump function. Therapy with MIA-602 significantly reduced tumor growth and enhanced the efficacy of doxorubicin in both cell lines. Control HCC1806 tumors grew by 435%, while the volume of tumors treated with MIA-602 enlarged by 172.2% and with doxorubicin by 201.6%. Treatment with the combination of MIA-602 and doxorubicin resulted in an increase in volume of only 76.2%. Control MX-1 tumors grew by 907%, while tumors treated with MIA-602 enlarged by 434.8% and with doxorubicin by 815%. The combination of MIA-602 and doxorubicin reduced the increase in tumor volume to 256%. Treatment with MIA-602 lowered the level of growth hormone-releasing hormone and growth hormone-releasing hormone receptors and significantly reduced the expression of multidrug resistance (MDR1) gene and the drug resistance regulator NANOG. MIA-602 also suppressed efflux pump function in both cell lines. We conclude that treatment of triple negative breast cancers with growth hormone-releasing hormone antagonists reduces tumor growth and potentiates the effects of cytotoxic therapy by nullifying drug resistance.

Effects of growth hormone-releasing hormone on sleep and brain interstitial fluid amyloid-β in an APP transgenic mouse model.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by impairment of cognitive function, extracellular amyloid plaques, intracellular neurofibrillary tangles, and synaptic and neuronal loss. There is substantial evidence that the aggregation of amyloid β (Aβ) in the brain plays a key role in the pathogenesis of AD and that Aβ aggregation is a concentration dependent process. Recently, it was found that Aβ levels in the brain interstitial fluid (ISF) are regulated by the sleep-wake cycle in both humans and mice; ISF Aβ is higher during wakefulness and lower during sleep. Intracerebroventricular infusion of orexin increased wakefulness and ISF Aβ levels, and chronic sleep deprivation significantly increased Aβ plaque formation in amyloid precursor protein transgenic (APP) mice. Growth hormone-releasing hormone (GHRH) is a well-documented sleep regulatory substance which promotes non-rapid eye movement sleep. GHRHR(lit/lit) mice that lack functional GHRH receptor have shorter sleep duration and longer wakefulness during light periods. The current study was undertaken to determine whether manipulating sleep by interfering with GHRH signaling affects brain ISF Aβ levels in APPswe/PS1ΔE9 (PS1APP) transgenic mice that overexpress mutant forms of APP and PSEN1 that cause autosomal dominant AD. We found that intraperitoneal injection of GHRH at dark onset increased sleep and decreased ISF Aβ and that delivery of a GHRH antagonist via reverse-microdialysis suppressed sleep and increased ISF Aβ. The diurnal fluctuation of ISF Aβ in PS1APP/GHRHR(lit/lit) mice was significantly smaller than that in PS1APP/GHRHR(lit/+) mice. However despite decreased sleep in GHRHR deficient mice, this was not associated with an increase in Aβ accumulation later in life. One of several possibilities for the finding is the fact that GHRHR deficient mice have GHRH-dependent but sleep-independent factors which protect against Aβ deposition.

Novel GHRH antagonists suppress the growth of human malignant melanoma by restoring nuclear p27 function

Malignant melanoma is the deadliest form of skin cancer; the treatment of advanced and recurrent forms remains a challenge. It has recently been reported that growth hormone-releasing hormone (GHRH) receptor is involved in the pathogenesis of melanoma. Therefore, we investigated the effects of our new GHRH antagonists on a human melanoma cancer cell line. Antiproliferative effects of GHRH antagonists, MIA-602, MIA-606 and MIA-690, on the human melanoma cell line, A-375, were studied in vitro using the MTS assay. The effect of MIA-690 (5 μg/day 28 d) was further evaluated in vivo in nude mice bearing xenografts of A-375. Subcellular localization of p27 was detected with Western blot and immunofluorescent staining. MIA-690 inhibited the proliferation of A-375 cells in a dose-dependent manner (33% at 10 μM, and 19.2% at 5 μM, P < 0 .05 vs. control), and suppressed the growth of xenografted tumors by 70.45% (P < 0.05). Flow cytometric analysis of cell cycle effects following the administration of MIA-690 revealed a decrease in the number of cells in G2/M phase (from 19.7% to 12.9%, P < 0.001). Additionally, Western blot and immunofluorescent studies showed that exposure of A-375 cells to MIA-690 triggered the nuclear accumulation of p27. MIA-690 inhibited tumor growth in vitro and in vivo, and increased the translocation of p27 into the nucleus thus inhibiting progression of the cell cycle. Our findings indicate that patients with malignant melanoma could benefit from treatment regimens, which combine existing chemotherapy agents and novel GHRH-antagonists.

Growth hormone-releasing hormone antagonists abolish the transactivation of human epidermal growth factor receptors in advanced prostate cancer models.

Growth hormone-releasing hormone (GHRH) and its receptors have been implicated in a variety of cellular phenotypes related with tumorigenesis process. Human epidermal growth factor receptor family members (HER) such as EGFR and HER2 are involved in mitogenic signaling pathways implicated in the progression of prostate cancer. We analyzed the cross-talk between GHRH and EGF receptors in prostate cancer. The effects of GHRH in HER signaling were evaluated on human androgen-independent PC3 prostate cancer cells in vitro and GHRH antagonist in vitro and in nude mice xenografts of PC3 prostate cancer. Time-course studies indicated that GHRH had a stimulatory activity on both the expression of EGFR and HER2. GHRH analogues, JMR-132 and JV-1-38, endowed with antagonistic activity for GHRH receptors, abrogated the response to GHRH in PC3 cells. GHRH stimulated a rapid ligand-independent activation of EGFR and HER2 involving at least cAMP/PKA and Src family signaling pathways. GHRH also stimulated a slow ligand-dependent activation of EGFR and HER2 involving an extracellular pathway with an important role for ADAM. Preliminary results also revealed an increase of mRNA for GHRH and GHRH receptor induced by EGF. The inhibition of tumor growth, in vivo, was associated with a substantial reduction in the expression of mRNA and protein levels of EGFR and HER2 in the tumors. GHRH antagonist JV-1-38, significantly decreased the phosphorylated Src levels. The cross-talk between HER and GHRH-R may be impeded by combining drugs acting upon GHRH receptors and HER family members in human advanced prostate cancer.

Prognosis in human glioblastoma based on expression of ligand growth hormone-releasing hormone, pituitary-type growth hormone-releasing hormone receptor, its splicing variant receptors, EGF receptor and PTEN genes.

Glioblastoma (GB) is the most frequent brain tumor. Despite recent improvement in therapeutic strategies, the prognosis of GB remains poor. Growth hormone-releasing hormone (GHRH) may act as a growth factor; antagonists of GHRH have been successfully applied for experimental treatment of different types of tumors. The expression profile of GHRH receptor, its main splice variant SV1 and GHRH have not been investigated in human GB tissue samples. We examined the expression of GHRH, full-length pituitary-type GHRH receptor (pGHRHR), its functional splice variant SV1 and non-functional SV2 by RT-PCR in 23 human GB specimens. Epidermal growth factor receptor (EGFR) and phosphatase and tensin homolog gene (PTEN) expression levels were also evaluated by quantitative RT-PCR. Correlations between clinico-pathological parameters and gene expressions were analyzed. Expression of GHRH was found to be positive in 61.9 % of samples. pGHRH receptor was not expressed in our sample set, while SV1 could be detected in 17.4 % and SV2 in 8.6 % of the GB tissues. In 65.2 and 78.3 % of samples, significant EGFR over-expression or PTEN under-representation could be detected, respectively. In 47.8 % of cases, EGFR up-regulation and PTEN down-regulation occurred together. Survival was significantly poorer in tumors lacking GHRH expression. This worse prognosis in GHRH negative group remained significant even if SV1 was also expressed. Our study shows that GHRH and SV1 genes expressed in human GB samples and their expression patterns are associated with poorer prognosis.

Preclinical efficacy of growth hormone-releasing hormone antagonist MIA-602 for androgen-dependent and castration-resistant human prostate cancer.

221 Background: Advanced hormone-sensitive prostate cancer (PCa) responds to androgen deprivation therapy (ADT). However, therapeutic options for castration-resistant disease are limited. As growth hormone-releasing hormone receptor (GHRH-R) and ligand GHRH are regulated in an autocrine fashion in PCa, GHRH-R inhibition represents a novel approach to PCa treatment. We investigated the effects of a new, highly potent GHRH antagonist, MIA-602, on growth of androgen-dependent and castration-resistant PCa cells in vitro/in vivo. Methods: All three cell lines used in this study expressed androgen receptors (ARs). 22Rv1 cells are castration-resistant and also express clinically relevant AR splice variants. LNCaP and VCaP lines are androgen dependent models that progress to castration resistance following ADT. Protein and mRNA levels of GHRH-R and its biologically active splice variant, SV1, were evaluated in cell lines and tumors by immunoblot and real-time RT-PCR. The influence of MIA-602 on cell proliferation and tumor formation was examined. Results: GHRH-R and SV1 were present in 22Rv1, LNCaP, and VCaP. LNCaP and VCaP cells expressed higher levels of GHRH-R protein compared to 22Rv1. However, 22Rv1 expressed higher levels of SV1. Inhibition of GHRH-R using MIA-602 decreased cell proliferation in vitro of 22Rv1, LNCaP, and VCaP PCa cell lines respectively by 70.4%, 60.7% and 20.3% (P&lt;0.05 for all). MIA-602 decreased 22Rv1 xenograft volumes in mice by 63% after 3 weeks of treatment. VCaP showed a substantial inhibition of xenograft growth following therapy with MIA-602 in vivo. MIA-602 effectively inhibited VCaP xenografts as a single agent or in combination with ADT by surgical castration. Conclusions: The effectiveness of the novel Miami class GHRH antagonist, MIA-602, in inhibiting growth of androgen-dependent and castration-resistant PCa models in vitro and in vivo was demonstrated. The inhibitory effect of GHRH antagonists appear to be due to effects exerted through GHRH receptors on cancer cells and/or possibly by indirect mechanisms. Further investigations of GHRH antagonists for PCa treatment are warranted.

Preclinical efficacy of growth hormone-releasing hormone antagonists for androgen-dependent and castration-resistant human prostate cancer

Advanced hormone-sensitive prostate cancer responds to androgen-deprivation therapy (ADT); however, therapeutic options for recurrent castration-resistant disease are limited. Because growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) are regulated in an autocrine fashion in prostate cancer, inhibition of GHRH-R represents a compelling approach to treatment. We investigated the effects of the latest series of improved, highly potent GHRH antagonists--MIA-602, MIA-606, and MIA-690--on the growth of androgen-dependent as well as castration-resistant prostate cancer (CRPC) cells in vitro and in vivo. GHRH-R and its splice variant, SV1, were present in 22Rv1, LNCaP, and VCaP human prostate cancer cell lines. Androgen-dependent LNCaP and VCaP cells expressed higher levels of GHRH-R protein compared with castration-resistant 22Rv1 cells; however, 22Rv1 expressed higher levels of SV1. In vitro, MIA-602 decreased cell proliferation of 22Rv1, LNCaP, and VCaP prostate cancer cell lines by 70%, 61%, and 20%, respectively (all P < 0.05), indicating direct effects of MIA-602. In vivo, MIA-602 was more effective than MIA-606 and MIA-690 and decreased 22Rv1 xenograft tumor volumes in mice by 63% after 3 wk (P < 0.05). No noticeable untoward effects or changes in body weight occurred. In vitro, the VCaP cell line was minimally inhibited by MIA-602, but in vivo, this line showed a substantial reduction in growth of xenografts in response to MIA-602, indicating both direct and systemic inhibitory effects. MIA-602 also further inhibited VCaP xenografts when combined with ADT. This study demonstrates the preclinical efficacy of the GHRH antagonist MIA-602 for treatment of both androgen-dependent and CRPC.

Growth hormone releasing hormone (GHRH) signaling modulates intermittent hypoxia‐induced oxidative stress and cognitive deficits in mouse

Intermittent hypoxia (IH) during sleep, such as occurs in obstructive sleep apnea (OSA), leads to degenerative changes in the hippocampus, and is associated with spatial learning deficits in adult mice. In both patients and murine models of OSA, the disease is associated with suppression of growth hormone (GH) secretion, which is actively involved in the growth, development, and function of the central nervous system (CNS). Recent work showed that exogenous GH therapy attenuated neurocognitive deficits elicited by IH during sleep in rats. Here, we show that administration of the Growth Hormone Releasing Hormone (GHRH) agonist JI-34 attenuates IH-induced neurocognitive deficits, anxiety, and depression in mice along with reduction in oxidative stress markers such as MDA and 8-hydroxydeoxyguanosine, and increases in hypoxia inducible factor-1α DNA binding and up-regulation of insulin growth factor-1 and erythropoietin expression. In contrast, treatment with a GHRH antagonist (MIA-602) during intermittent hypoxia did not affect any of the IH-induced deleterious effects in mice. Thus, exogenous GHRH administered as the formulation of a GHRH agonist may provide a viable therapeutic intervention to protect IH-vulnerable brain regions from OSA-associated neurocognitive dysfunction. Sleep apnea, characterized by chronic intermittent hypoxia (IH), is associated with substantial cognitive and behavioral deficits. Here, we show that administration of a GHRH agonist (JI-34) reduces oxidative stress, increases both HIF-1α nuclear binding and downstream expression of IGF1 and erythropoietin (EPO) in hippocampus and cortex, and markedly attenuates water maze performance deficits in mice exposed to intermittent hypoxia during sleep.

Combination of GHRH antagonists and docetaxel shows experimental effectiveness for the treatment of triple-negative breast cancers

In preclinical studies, antagonists of growth hormone-releasing hormone (GHRH) have demonstrated inhibitory effects on the growth of various types of cancers expressing the pituitary type of GHRH receptors (pGHRH-R) and/or its active splice variant 1 (SV1). In this study, we investigated the effectiveness of the treatment of MDA-MB-231 human triple-negative breast cancer (TNBC) with GHRH antagonist JMR-132 alone or in combination with docetaxel. Receptor expression in the MDA-MB-231 human breast cancer cell line was evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Cell viability assays were performed on MDA-MB-231 cells treated with JMR-132, docetaxel or in combination. For studies in vivo, a subcutaneous nude mouse xenograft model was used. JMR-132 was administered s.c. at a dose of 10 µg/day and docetaxel at a dose of 10 mg/kg i.p. given on day 1 and 5. Similar regimens were used for the combination of both substances. At the end of the experiment, an mRNA-based human cancer pathway array including 84 major genes was performed on the tumor tissue of mice treated with JMR-132 to elucidate the mechanism of action of GHRH antagonists in vivo. The in vitro proliferation studies revealed that JMR-132 and docetaxel decreased the cell viability in a dose-dependent manner. The combination of both treatments produced a significantly greater inhibition of cell viability compared to the single agents. Treatment of nude mice bearing MDA-MB-231 xenografts with JMR-132 and docetaxel significantly (p<0.05) inhibited tumor growth by 46 and 50%, respectively. Treatment with the combination of JMR-132 and docetaxel led to an inhibition of tumor volume by 71.6% (p<0.001). Polymerase chain reaction array analysis revealed that JMR-132 interacts with signal transduction pathways involved in proliferation, apoptosis and angiogenesis. Our results suggest that GHRH antagonists in combination with taxanes may enhance the efficacy of treatment for patients with TNBC expressing the SV1 and/or the pGHRH receptor.

Abstract 4769: Growth hormone-releasing hormone (GHRH) antagonist attenuates cell motility of human endometrial cancer by down-regulating Twist and N-Cadherin expression.

Abstract Introduction : More than 25% of patients diagnosed with endometrial carcinoma have an invasive primary cancer accompanied by metastases. GHRH is secreted by the hypothalamus and stimulates the synthesis and secretion of GH from the pituitary. The expression of GHRH and its receptors has been demonstrated in peripheral tissues. In recent years, many antagonistic analogs of GHRH were developed. GHRH antagonists have effects on tumor cells, but the underlying molecular mechanism is not well known. Although Twist and N-Cadherin play important roles in cancer cell motility, it is not established whether Twist and N-Cadherin are required for GHRH antagonists-attenuated cell motility on endometrial cancer cells. In the present study, we examined the action of GHRH antagonist-attenuated cell motility and the mechanisms of the action in endometrial cancer. Methods and Materials : Endometrial cancer cell line Ishikawa and ECC-1 were derived from an endometrial adenocarcinoma. GHRH antagonist MIA-602 was synthesized by solid phase methods. Cell motility was estimated by invasion and migration assay. Immunoblot analysis and RT-PCR were performed to investigate the expression of GHRH receptor, GHRH, and the effects of GHRH antagonist in Twist and N-Cadherin. Human GHRH receptor siRNA was used to knock down the expression of GHRH receptor for elucidating the mechanisms of GHRH antagonist action. Results : The GHRH receptor was expressed in human endometrial cancer cells. The GHRH antagonist attenuated cell motility in a dose-dependent manner. GHRH antagonist-attenuated cell motility was restored in cells pretreated with GHRH receptor siRNA. GHRH antagonist suppressed Twist and N-Cadherin signaling. Knockdown of GHRH receptor with siRNA recovered the expression of Twist and N-Cadherin signaling. Conclusions These results demonstrate that the GHRH antagonist suppressed the cell motility of human endometrial cancer through the GHRH receptor and the down-regulation of Twist and N-Cadherin. Our findings represent a new concept regarding the mechanisms of GHRH antagonist-suppressed cell motility in human endometrial cancer, suggesting the possibility of GHRH antagonist as a potential therapeutic intervention for the treatment of human endometrial cancer. Citation Format: Hsien-Ming Wu, Andrew V. Schally, Peter C.K. Leung. Growth hormone-releasing hormone (GHRH) antagonist attenuates cell motility of human endometrial cancer by down-regulating Twist and N-Cadherin expression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4769. doi:10.1158/1538-7445.AM2013-4769 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract 91: Powerful inhibition of human renal cell carcinomas with antagonists of growth hormone-releasing hormone (GHRH): a preclinical study.

Abstract BACKGROUND: Advances in targeted medical thereapy has demonstrated improved clinical outcomes for patients with metastatic renal cell carcinoma (RCC), however, a complete response is rare and current therapy has various adverse effects that are unfortunately not as rare. Early antagonists of growth hormone-releasing hormone (GHRH) were shown to inhibit experimental RCC cell line, Caki-1, in vitro and in vivo. GHRH itself acts as an autocrine/paracrine growth factor in human cancers, including RCC. Herein, we investigate the effects of novel and highly potent new antagonists of GHRH on the growth of three RCC cell lines with different primary tumor sites. METHODS: The expression of GHRH receptor in all three cell lines was evaluated by ligand competition studies. The in vitro influence of GHRH antagonists designated MIA-602, MIA-604, MIA-606 and MIA-690 on cell viability was assessed by MTS assay in ACHN, A498, and 786-0 human RCC cells. GHRH antagonists were given at a dose of 5μg daily in these three nude-mice xenograft models in vivo. Cell cycle parameters were analyzed by laser flow cytometry. RESULTS: Ligand competition studies revealed specific, high affinity binding sites for GHRH receptor in all three RCC cell lines. GHRH antagonists inhibited the proliferation of all three RCC cells in a dose dependent manner. GHRH antagonists caused significant inhibition of tumor growth of ACHN, A498, and 786-0 RCCs ranging from 53-75% after 35 days of treatment (p&amp;lt;0.001). Treatment of ACHN and A498 cells with 10μM MIA-602 and MIA-690 (5 and 10μM) led to a significant increase in number of cells with subG1 DNA content, suggesting apoptosis. CONCLUSIONS: The effectiveness of the new and novel GHRH antagonists in inhibiting growth of experimental RCC models in vitro and in vivo was demonstrated. The inhibitory effect of GHRH antagonists is mainly due to direct suppressive effects exerted through GHRH receptors. Further biochemical and histological evaluation is warranted to explore the mechanisms of action of GHRH antagonists in RCC. Citation Format: Ferenc G. Rick, Andrew Abi-Chaker, Luca Szalontay, Norman L. Block, Gabor Halmos, Mehrdad Nadji, Andrew V. Schally. Powerful inhibition of human renal cell carcinomas with antagonists of growth hormone-releasing hormone (GHRH): a preclinical study. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 91. doi:10.1158/1538-7445.AM2013-91

Effect of novel growth hormone-releasing hormone antagonists on growth of experimental renal cell carcinomas.

469 Background: Although targeted therapy has improved the clinical outcome for patients with metastatic renal cell carcinoma (RCC), a complete response is rare and therapy has adverse effects. Early antagonists of growth hormone-releasing hormone (GHRH) were shown to inhibit experimental RCC cell line, Caki-1, in vitro and in vivo. Herein, we investigate the effects of novel and highly potent antagonists of GHRH of MIA class on the growth of three RCC cell lines. Methods: The expression of GHRH receptor in all three cell lines was evaluated by ligand competition studies. The influence of GHRH antagonists MIA-602, MIA-604, MIA-606, and MIA-690 on cell viability was assessed by MTS assay in ACHN, A498, and 786-0 human RCC cells. GHRH antagonists were given at dose of 5µg daily in these three nude-mice xenograft models. Cell cycle parameters were analyzed by laser flow cytometry. Results: Ligand competition studies revealed specific, high affinity binding sites for GHRH receptor in all three RCC cell lines. GHRH antagonists inhibited the proliferation of all three RCC cells in a dose dependent manner. GHRH antagonists caused significant inhibition of tumor growth of ACHN, A498, and 786-0 RCCs ranged from 53-75% after 35 days of treatment (p&lt;0.001). Treatment of ACHN cells with MIA-690 (10µM) led to a significant increase in number of cells with subG1DNA content, suggesting apoptosis. Conclusions: The effectiveness of the novel GHRH antagonists in inhibiting growth of experimental RCC models in vitro and in vivo was demonstrated. The inhibitory effect of GHRH antagonists is mainly due to direct inhibitory effects exerted through GHRH receptors. Biochemical and histological evaluation is needed to explore the mechanisms of action of GHRH antagonists in RCC.

Suppression of the proliferation of human U-87 MG glioblastoma cells by new antagonists of growth hormone-releasing hormone in vivo and in vitro

Five-year survival of patients afflicted with glioblastoma multiforme (GBM) is rare, making this cancer one of the most feared malignancies. Previously, we reported that growth hormone-releasing hormone (GHRH) is a potent growth factor in cancers. The present work evaluated the effects of two antagonistic analogs of GHRH (MIA-604 and MIA-690) on the proliferation of U-87 MG GBM tumors, in vivo as well as in vitro. Both analogs were administered subcutaneously and dose-dependently inhibited the growth of tumors transplanted into nude mice (127 animals in seven groups). The analogs also inhibited cell proliferation in vitro, decreased cell size, and promoted apoptotic and autophagic processes. Both antagonists stimulated contact inhibition, as indicated by the expression of the E-cadherin-β-catenin complex and integrins, and decreased the release of humoral regulators of glial growth such as FGF, PDGFβ, and TGFβ, as revealed by genomic or proteomic detection methods. The GHRH analogs downregulated other tumor markers (Jun-proto-oncogene, mitogen-activated protein kinase-1, and melanoma cell adhesion molecule), upregulated tumor suppressors (p53, metastasis suppressor-1, nexin, TNF receptor 1A, BCL-2-associated agonist of cell death, and ifκBα), and inhibited the expression of the regulators of angiogenesis and invasion (angiopoetin-1, VEGF, matrix metallopeptidase-1, S100 calcium binding protein A4, and synuclein-γ). Our findings indicate that GHRH antagonists inhibit growth of GBMs by multiple mechanisms and decrease both tumor cell size and number.

Hormonal manipulation of benign prostatic hyperplasia

We provide new viewpoints of hormonal control of benign prostatic hyperplasia (BPH). The latest treatment findings with 5-alpha reductase inhibitors (5-ARIs) finasteride and dutasteride, refined indications, efficacy, and safety are discussed and compared. We also discuss potential new 5-ARIs and other hormonal treatments. Finasteride and dutasteride have equal efficacy and safety for the treatment and prevention of progression of BPH. 5-ARIs are especially recommended for prostates greater than 40 ml and PSA greater than 1.5 ng/ml. Combination therapy is the treatment of choice in these patients, but with prostate volume greater than 58 ml or International Prostate Symptom Score of at least 20, combinations have no advantage over 5-ARI monotherapy. Updates on the recent developments on BPH therapy with luteinizing hormone-releasing hormone (LHRH) antagonist are also reviewed and analyzed. Preclinical studies suggest that growth hormone-releasing hormone (GHRH) antagonists effectively shrink experimentally enlarged prostates alone or in combination with LHRH antagonists. New 5-ARIs seem to be the promising agents that need further study. Preclinical studies revealed that GHRH and LHRH antagonists both can cause a reduction in prostate volume. Recent data indicate that prostate shrinkage is induced by the direct inhibitory action of GHRH and of LHRH antagonists exerted through prostatic receptors. The adverse effects of 5ARIs encourage alternative therapy.

Mechanisms of synergism between antagonists of growth hormone‐releasing hormone and antagonists of luteinizing hormone‐releasing hormone in shrinking experimental benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) affects aging men. Combined therapy with antagonists of growth hormone-releasing hormone (GHRH) and of luteinizing hormone-releasing hormone (LHRH or GnRH) induces prostate shrinkage in rat models. We investigated the mechanisms of action of this combination on cell cycle traverse and expression of prostatic genes. Effects of GHRH antagonist, JMR-132 (40 µg/day), the LHRH antagonist, cetrorelix (0.625 mg/kg), and their combination were evaluated on testosterone-induced benign prostatic hyperplasia in male Wistar rats. Influence of JMR-132, cetrorelix, and their combinations on cell viability was assessed by MTS assay in BPH-1 human prostate epithelial cells and WPMY-1 normal prostate stromal cells. Cell cycle was analyzed by laser flow cytometry. Real-time PCR arrays were performed. The combination of antagonists caused marked shrinkage of rat prostate (29.5%). In vitro, JMR-132 plus cetrorelix (both 5µM) produced synergistic (57.4%) inhibition of growth of BPH-1 cells, but a lesser inhibition (46%) of WPMY-1 cells. Co-treatment of with JMR-132 plus cetrorelix induced a significant increase of BPH-1 cells blocked in S-phase plus cells with lower G0 /G1 and G2 /M DNA content. Significant changes in expression of >40 gene transcripts related to growth factors, inflammatory cytokines, and signal transduction were identified. GHRH antagonist and LHRH antagonist combination potentiates rat prostate weight reduction and synergistically inhibits of growth of BPH-1 leading to cell cycle arrest in S-phase. These effects were lesser in normal stromal prostate cell line, WPMY-1. Our findings suggest that GHRH antagonists could be useful for BPH therapy, possibly in combination with LHRH antagonists.

Anti-tumor effects of peptide analogs targeting neuropeptide hormone receptors on mouse pheochromocytoma cells

Pheochromocytoma is a rare but potentially lethal chromaffin cell tumor with currently no effective treatment. Peptide hormone receptors are frequently overexpressed on endocrine tumor cells and can be specifically targeted by various anti-tumor peptide analogs. The present study carried out on mouse pheochromocytoma cells (MPCs) and a more aggressive mouse tumor tissue-derived (MTT) cell line revealed that these cells are characterized by pronounced expression of the somatostatin receptor 2 (sst2), growth hormone-releasing hormone (GHRH) receptor and the luteinizing hormone-releasing hormone (LHRH) receptor. We further demonstrated significant anti-tumor effects mediated by cytotoxic somatostatin analogs, AN-162 and AN-238, by LHRH antagonist, Cetrorelix, by the cytotoxic LHRH analog, AN-152, and by recently developed GHRH antagonist, MIA-602, on MPC and for AN-152 and MIA-602 on MTT cells. Studies of novel anti-tumor compounds on these mouse cell lines serve as an important basis for mouse models of metastatic pheochromocytoma, which we are currently establishing.

Beneficial effects of novel antagonists of GHRH in different models of Alzheimer's disease

Alzheimer's disease is the most frequent debilitating disorder of the central nervous system. Neuroendocrine mechanisms appear to play an important role in this insidiously developing disease. In the present study, the effects of a recently developed growth hormone-releasing hormone (GHRH) antagonist (MIA-690) were evaluated in vivo observing the behavior of genetically modified "Alzheimer's" 5XFAD mice in a Morris water maze (MWM). The effects of the antagonist were also evaluated in vitro using HCN2 human cortical cell cultures treated with amyloid-β1-42. In vivo, the indices of cognitive performance (latency, cumulative index etc.) were followed up for 6 months. In vitro, the formation of reactive oxygen species, markers of inflammatory and neurohormonal signaling were measured by fluorescent detection, PCR, and ELISA. Accumulation of amyloid-β1-42 rafts and τ filaments in necropsied brain samples was verified with the help of ELISA. In the MWM experiments, MIA-690 decreased escape latency, and, in the brain samples, it inhibited the concentration of amyloid-β1-42 and τ filaments. In cell cultures, the GHRH analog showed anti-oxidative and neuro-protective properties and inhibited the GHRH-growth hormone-insulin like growth factor axis. Our data strongly suggest the merit of further studies with GHRH analogs in models of Alzheimer's disease and in elementary clinical trials.

GHRH antagonist when combined with cytotoxic agents induces S-phase arrest and additive growth inhibition of human colon cancer

Treatment of colon cancer with an antagonist of growth hormone-releasing hormone (GHRH), JMR-132, results in a cell cycle arrest in S-phase of the tumor cells. Thus, we investigated the effect of JMR-132 in combination with S-phase-specific cytotoxic agents, 5-FU, irinotecan and cisplatin on the in vitro and in vivo growth of HT-29, HCT-116 and HCT-15 human colon cancer cell lines. In vitro, every compound inhibited proliferation of HCT-116 cells in a dose-dependent manner. Treatment with JMR-132 (5 μM) combined with 5-FU (1.25 μM), irinotecan (1.25 μM) or cisplatin (1.25 μM) resulted in an additive growth inhibition of HCT-116 cells in vitro as shown by MTS assay. Cell cycle analyses revealed that treatment of HCT-116 cells with JMR-132 was accompanied by a cell cycle arrest in S-phase. Combination treatment using JMR-132 plus a cytotoxic drug led to a significant increase of the sub-G1 fraction, suggesting apoptosis. In vivo, daily treatment with GHRH antagonist JMR-132 decreased the tumor volume by 40–55% (p < 0.001) of HT-29, HCT-116 and HCT-15 tumors xenografted into athymic nude mice. Combined treatment with JMR-132 plus chemotherapeutic agents 5-FU, irinotecan or cisplatin resulted in an additive tumor growth suppression of HT-29, HCT-116 and HCT-15 xenografts to 56–85%. Our observations indicate that JMR-132 enhances the antiproliferative effect of S-phase-specific cytotoxic drugs by causing accumulation of tumor cells in S-phase.