title: Synthesis and structure-activity studies on novel analogs of human growth hormone releasing hormone (GHRH) with enhanced inhibitory activities on tumor growth.
abstract: The syntheses and biological evaluations of new GHRH analogs of Miami (MIA) series with greatly increased anticancer activity are described. In the design and synthesis of these analogs, the following previous substitutions were conserved: D-Arg2, Har9, Abu15, and Nle27. Most new analogs had Ala at position 8. Since replacements of both Lys12and Lys21with Orn increased resistance against enzymatic degradation, these modifications were kept. The substitutions of Arg at both positions 11 and 20 by His were also conserved. We kept D-Arg28, Har29-NH2at the C-terminus or inserted Agm or 12-amino dodecanoic acid amide at position 30. We incorporated pentafluoro-Phe (Fpa5), instead of Cpa, at position 6 and Tyr(Me) at position 10 and ω-amino acids at N-terminus of some analogs. These GHRH analogs were prepared by solid-phase methodology and purified by HPLC. The evaluation of the activity of the analogs on GH release was carried out in vitro on rat pituitaries and in vivo in male rats. Receptor binding affinities were measured in vitro by the competitive binding analysis. The inhibitory activity of the analogs on tumor proliferation in vitro was tested in several human cancer cell lines such as HEC-1A endometrial adenocarcinoma, HCT-15 colorectal adenocarcinoma, and LNCaP prostatic carcinoma. For in vivo tests, various cell lines including PC-3 prostate cancer, HEC-1A endometrial adenocarcinoma, HT diffuse mixed β cell lymphoma, and ACHN renal cell carcinoma cell lines were xenografted into nude mice and treated subcutaneously with GHRH antagonists at doses of 1-5μg/day. Analogs MIA-602, MIA-604, MIA-610, and MIA-640 showed the highest binding affinities, 30, 58, 48, and 73 times higher respectively, than GHRH (1-29) NH2. Treatment of LNCaP and HCT-15 cells with 5μM MIA-602 or MIA-690 decreased proliferation by 40%-80%. In accord with previous tests in various human cancer lines, analog MIA-602 showed high inhibitory activity in vivo on growth of PC-3 prostate cancer, HT-mixed β cell lymphoma, HEC-1A endometrial adenocarcinoma and ACHN renal cell carcinoma. Thus, GHRH analogs of the Miami series powerfully suppress tumor growth, but have only a weak endocrine GH inhibitory activity. The suppression of tumor growth could be induced in part by the downregulation of GHRH receptors levels.
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Marta
authors.initials: M
authors.lastname: Zarandi
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Division of Endocrinology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Renzhi
authors.initials: R
authors.lastname: Cai
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Magdolna
authors.initials: M
authors.lastname: Kovacs
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Division of Endocrinology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Petra
authors.initials: P
authors.lastname: Popovics
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Luca
authors.initials: L
authors.lastname: Szalontay
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Division of Endocrinology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Tengjiao
authors.initials: T
authors.lastname: Cui
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; Division of Endocrinology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Division of Hematology/Oncology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Sylvester Comprehensive Cancer Center, Miami, FL, United States.
authors.forename: Wei
authors.initials: W
authors.lastname: Sha
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Miklos
authors.initials: M
authors.lastname: Jaszberenyi
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States.
authors.forename: Jozsef
authors.initials: J
authors.lastname: Varga
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: XianYang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Sylvester Comprehensive Cancer Center, Miami, FL, United States; Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, Miami, FL, United States.
authors.forename: Norman L
authors.initials: NL
authors.lastname: Block
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Urology, Florida International University, Herbert Wertheim College of Medicine, Miami, FL, United States.
authors.forename: Ferenc G
authors.initials: FG
authors.lastname: Rick
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States.
authors.forename: Gabor
authors.initials: G
authors.lastname: Halmos
authors.affiliation: Endocrine, Polypeptide, and Cancer Institute, Veterans Affairs Medical Center, Miami, FL, United States; South Florida VA Foundation for Research and Education, Miami, FL, United States; Department of Pathology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Division of Endocrinology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Division of Hematology/Oncology, Department of Medicine, University of Miami Miller School of Medicine, Miami, FL, United States; Sylvester Comprehensive Cancer Center, Miami, FL, United States. Electronic address: andrew.schally@va.gov.
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Schally
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D013006:Growth Hormone / Q000096:biosynthesis* / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000138:chemical synthesis; D006801:Humans; D051379:Mice; D009369:Neoplasms / Q000188:drug therapy* / Q000473:pathology; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone
keywords: Cancer inhibition; Growth hormone releasing hormone; Hormone antagonist; Hypothalamic hormones; SAR studies; hGHRH antagonist