Structure and function of a dual antagonist of the human growth hormone and prolactin receptors with site-specific PEG conjugates

Human growth hormone (hGH) is a pituitary-derived endocrine protein that regulates several critical postnatal physiologic processes including growth, organ development, and metabolism. Following adulthood, GH is also a regulator of multiple pathologies like fibrosis, cancer, and diabetes. Therefore, there is a significant pharmaceutical interest in developing antagonists of hGH action. Currently, there is a single FDA-approved antagonist of the hGH receptor (hGHR) prescribed for treating patients with acromegaly and discovered in our laboratory almost 3 decades ago. Here, we present the first data on the structure and function of a new set of protein antagonists with the full range of hGH actions—dual antagonists of hGH binding to the GHR as well as that of hGH binding to the prolactin receptor. We describe the site-specific PEG conjugation, purification, and subsequent characterization using MALDI-TOF, size-exclusion chromatography, thermostability, and biochemical activity in terms of ELISA-based binding affinities with GHR and prolactin receptor. Moreover, these novel hGHR antagonists display distinct antagonism of GH-induced GHR intracellular signaling in vitro and marked reduction in hepatic insulin-like growth factor 1 output in vivo. Lastly, we observed potent anticancer biological efficacies of these novel hGHR antagonists against human cancer cell lines. In conclusion, we propose that these new GHR antagonists have potential for development towards multiple clinical applications related to GH-associated pathologies.</p

Cis Di-oxomolybdenum(VI) Complexes with a Tridentate ONO Donor Ligand; Synthesis, X-ray Crystal Structure, Spectroscopic Properties and Oxotransfer Chemistry

The molybdenum complexes of Schiff base ligands viz. [MoO2LH2O] where L1 = tris(hydroxymethyl)(salicylide-neamino)methane, L2 = tris(hydroxymethyl)(2,3-dihydroxybenzylideneamino)methane and L3 = tris(hydroxymethyl)(2,3,4-trihydroxybenzylideneamino)methane have been synthesized and characterized by spectroscopic and electrochemical techniques. The X-ray crystal structure of the complex [MoO2L1H2O] reveals a distorted octahedral geometry with one ligand and a water molecule coordinated to the MoO2 center. No previous complex of this type contains a coordinated water molecule. The complex undergoes an oxotransfer in the presence of Bu3P to form a -oxobridged molybdenum(V,V) dimer. This rules out Mo—S coordination as a prerequisite for oxotransfer in such molybdenum(VI) complexes

Antimelanomal activity of the copper(II) complexes of 1-substituted 5-amino-imidazole ligands against B16F10 mouse melanoma cells

The copper complexes of 5-amino-imidazole ligands were prepared and characterized by various spectroscopic techniques. The ligand geometry around the copper(II) centre is square pyramidal based on N2O2 donor atoms and a coordinated water molecule at the apex. Single crystal X-ray structures were determined for both ligands. Ligands and copper complexes exhibited dose-dependent antiproliferative effects on the growth of B16F10 melanoma cells line but lower IC50 values were observed for the copper complexes. The copper complexes of 5-amino-imidazole ligands were prepared and characterized by various spectroscopic techniques. Ligands and copper complexes exhibited dose-dependent antiproliferative effects on the growth of B16F10 melanoma cells line but lower IC50 values were observed for the copper complexes

Metal Complexes as Anticancer Agents 2

The copper complex [Cu(ATICAR)2(H2O)]·2H2O (ATICAR = 5-amino-1-tolylimidazole-4-carboxylate) has been prepared and characterized by its crystal structure determination. The ligand geometry around the copper(II) center is best described as predominantly square pyramidal (2/3) with a trigonal bipyramidal component (1/3). The ATICAR ligands act as bidentates to form the distorted square pyramid base of N2O2 donor atoms and a coordinated water molecule at the apex is held with a Cu-O bond that is unusually short (2.148 A) for square pyramidal copper(II). Compound exhibits a dose-dependent antiproliferative effect on the growth of the B16F10 melanoma cell line while its lower IC50 value establish advantage by copper complexation. (C) 2000 Elsevier Science S.A