title: Novel GHRH antagonists suppress the growth of human malignant melanoma by restoring nuclear p27 function.
abstract: 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.
authors.affiliation: a Veterans Affairs Medical Center and South Florida Veterans Affairs Foundation for Research and Education ; Miami , FL USA.
authors.forename: Luca
authors.initials: L
authors.lastname: Szalontay
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Schally
authors.forename: Petra
authors.initials: P
authors.lastname: Popovics
authors.forename: Irving
authors.initials: I
authors.lastname: Vidaurre
authors.forename: Awtar
authors.initials: A
authors.lastname: Krishan
authors.forename: Marta
authors.initials: M
authors.lastname: Zarandi
authors.forename: Ren-Zhi
authors.initials: RZ
authors.lastname: Cai
authors.forename: Anna
authors.initials: A
authors.lastname: Klukovits
authors.forename: Norman L
authors.initials: NL
authors.lastname: Block
authors.forename: Ferenc G
authors.initials: FG
authors.lastname: Rick
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D013007:Growth Hormone-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D008819:Mice, Nude; D018013:Receptors, Neuropeptide / Q000378:metabolism; D018017:Receptors, Pituitary Hormone-Regulating Hormone / Q000378:metabolism; D017337:Sermorelin / Q000031:analogs & derivatives; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012878:Skin Neoplasms; D023041:Xenograft Model Antitumor Assays; D000096142:Cutaneous Malignant Melanoma
chemical_list: C550121:GHRH(1-29)NH2, (PhAc-Ada)(0)-Tyr(1), Arg(2), Fpa(5,6), Ala(8), Har(9), Tyr(Me)(10), His(11), Orn(12,) Abu(15), His(20), Orn(21), Nle(27), Arg(28), Har(29)-; D018013:Receptors, Neuropeptide; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017337:Sermorelin; D013007:Growth Hormone-Releasing Hormone; C048250:somatotropin releasing hormone receptor
keywords: ANOVA, one-way analysis of variance; Abu, a-aminobutyric acid; Ac, acetyl; Ada, 12-aminododecanoyl; Agm, agmatine; Amc, 8-aminocaprylyl; Cpa, parachlorophenylalanine; FBS, fetal bovine serum; Fpa5, pentafluoro-phenylalanine; GH, growth hormone; GHRH, growth hormone-releasing hormone; GHRH-R, growth hormone-releasing hormone receptor; Har, homoarginine; IGF-I, insulin-like growth factor I; MTS, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfonphenyl)-2H-tetrazolium; Nle, norleucine; Orn, ornithine; Ph, phenyl; PhAc, phenylacetyl; SVs, splice variants; TBS, tris-buffered saline; Tyr(Me), O-methyltyrosine; growth hormone-releasing hormone antagonist; hGHRH, human growth hormone-releasing hormone; mTOR, mammalian target of rapamycin; melanoma; p27; pGHRH-R, pituitary type GHRH-receptor; targeted therapy; xenografted mouse model