title: Metabotropic glutamate receptor 1 and glutamate signaling in human melanoma.
abstract: Recently, several laboratories have started to investigate the involvement of glutamate signaling in cancer. In previous studies, we reported on a transgenic mouse model that develops melanoma spontaneously. Subsequent studies in these mice identified that the aberrant expression of metabotropic glutamate receptor 1 (GRM1) in melanocytes played a critical role in the onset of melanoma. Confirmation of the etiologic role of GRM1 in melanoma development was shown in a second transgenic line with GRM1 expression under the regulation of a melanocyte-specific dopachrome tautomerase promoter. Ectopic expression of GRM1 was also detected in a subset of human melanoma cell lines and biopsies, suggesting that aberrant expression of GRM1 in melanocytes may contribute to the development of human melanoma. GRM1, a seven-transmembrane domain G protein-coupled receptor, is normally expressed and functional in neuronal cells, and its ligand, glutamate, is the major excitatory neurotransmitter. Human melanoma cells are shown here to release elevated levels of glutamate, implying a possible autocrine loop. Treatment of GRM1-expressing human melanoma cells with a GRM1 antagonist (LY367385 or BAY36-7620) or a glutamate release inhibitor (riluzole) leads to a suppression of cell proliferation as well as a decrease in levels of extracellular glutamate. Treatment of human melanoma cell xenografts with riluzole for 18 days via p.o. gavage or i.v. injection leads to inhibition of tumor growth by 50% in comparison with controls. These data suggest the importance of glutamate signaling in human melanoma and imply that the suppression of glutamate signaling may be a new target for melanoma therapy.
authors.affiliation: Susan Lehman Cullman Laboratory for Cancer Research, Department of Chemical Biology, Ernest Mario School of Pharmacy, Rutgers University, 164 Frelinghuysen Road, Piscataway, NJ 08854, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Namkoong
authors.forename: Seung-Shick
authors.initials: SS
authors.lastname: Shin
authors.forename: Hwa Jin
authors.initials: HJ
authors.lastname: Lee
authors.forename: Yarí E
authors.initials: YE
authors.lastname: Marín
authors.forename: Brian A
authors.initials: BA
authors.lastname: Wall
authors.forename: James S
authors.initials: JS
authors.lastname: Goydos
authors.forename: Suzie
authors.initials: S
authors.lastname: Chen
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis; D049109:Cell Proliferation / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D008545:Melanoma / Q000188:drug therapy / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D050505:Mutant Proteins / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D019782:Riluzole / Q000627:therapeutic use; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000188:drug therapy / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D050505:Mutant Proteins; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D018698:Glutamic Acid; D019782:Riluzole