Characterization of receptors for growth hormone-releasing hormone in human osteosarcomas and Ewing's sarcomas.

Abstract

Antagonists of growth hormone-releasing hormone (GH-RH) inhibit growth of various human cancers including osteosarcomas and Ewing's sarcomas, xenografted into nude mice or cultured in vitro. The antiproliferative effect of GH-RH antagonists could be mediated, in part, through the splice variants (SVs) of receptors for GH-RH which have been found in several human cancers and cancer cell lines. In this study we investigated the expression of SVs of GH-RH receptors and the binding characteristics of these receptor isoforms in MNNG/HOS human osteosarcoma and SK-ES-1 human Ewing's sarcoma grown in nude mice. RT-PCR revealed the presence of mRNA for SVs of GH-RH receptors in both human malignant bone cancer models. Using ligand competition assays with 125I-labeled GH-RH antagonist JV-1-42, we demonstrated in MNNG/HOS and SK-ES-1 tumors the presence of specific high affinity binding sites for GH-RH (Kd=5.83 nM and Kd=2.76 nM) with a maximal binding capacity (Bmax) of 552.1 fmol/mg protein and 371.9 fmol/mg protein, respectively. We also investigated the effect of GH-RH antagonist JV-1-38, administered s.c. at a dose of 20 microg twice daily for 4 weeks on the gene expression, affinity and concentration of receptors for GH-RH in MNNG/HOS human osteosarcomas xenografted into nude mice. Treatment with JV-1-38 did not affect the expression and binding characteristics of GH-RH receptors. High affinity binding of JV-1-38 to GH-RH receptors on MNNG/HOS tumors was characterized by an IC50 value of 1.04 nM. The presence of GH-RH receptors in human bone tumors provides a rationale for new approaches to the therapy of this malignancy based on GH-RH antagonists.

• Authors: Gabor Halmos, Andrew V Schally, Andrea L F Bernardino, Jozsef L Varga
• Journal: International journal of oncology (Int J Oncol) Vol. 29 Issue 2 Pg. 463-9 (Aug 2006) ISSN: 1019-6439 [Print] Greece
• PMID: 16820890 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Receptors, Neuropeptide
• Receptors, Pituitary Hormone-Regulating Hormone
• Growth Hormone-Releasing Hormone
• somatotropin releasing hormone receptor

Topics

• Animals
• Cell Line, Tumor
• Growth Hormone-Releasing Hormone (chemistry, metabolism)
• Humans
• Inhibitory Concentration 50
• Kinetics
• Mice
• Neoplasm Transplantation
• Osteosarcoma (metabolism)
• Protein Binding
• Receptors, Neuropeptide (chemistry)
• Receptors, Pituitary Hormone-Regulating Hormone (chemistry)
• Sarcoma, Ewing (metabolism)