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A zinc(II) containing configurationally restricted analogue of bismacrocyclic cyclam-type CXCR4 chemokine receptor antagonists has been synthesized and shown to adopt only one configuration in solution. The single crystal X-ray structure reveals favorable binding to acetate via a bidentate chelation that can be related to the proposed interaction with aspartate on the receptor protein surface. The zinc(II) complex is highly active against HIV infection in vitro. AMD3100 (the octa HCl salt of 1-1′-[1,4-phenylenebis-(methylene)]-bis(1,4,8,11-tetraazacyclotetradecane)), Figure 1c, is a drug that interacts with a cell surface protein (CXCR4) via hydrogen bonding interactions or more effectively as the metal complex via coordinate bonds with aspartate residues. 1 On metal complex formation, the tetra-aza macrocyclic rings in AMD3100 show multiple configurations in solution. 2 Configurationally fixed analogues would have the advantage of presenting only one configuration in solution for coordinate bond formation on binding to the protein. Our study aims to produce a series of configurationally fixed complexes and show the key importance of the coordination interaction for drug binding. We also wish to validate the general strategy of configurational fixing as a route to improve the activity of metal-containing drugs.The CXCR4 chemokine receptor is a seven-helix transmembrane G-protein coupled receptor with multiple critical functions in both normal and pathological physiology. It is a member of the family of 18 recognized chemokine receptors and has a sole natural ligand (CXCL12). 3 Synthetic small molecule antagonists exist, including AMD3100, and have been shown to have both a high binding specificity and an effective inhibitory action against a number of disease states. 4,5 For example, in vitro assays show that AMD3100 inhibits infection by the human immunodeficiency virus (HIV-1 and HIV-2) at micromolar concentrations. 6 It has been demonstrated that formation of metal complexes and aza-macrocyclic ring configuration may have major effects on AMD3100-protein interactions. 1,2,[7][8][9] In particular, it has been suggested that zinc(II) could play a key role in the biological activity of the bicyclam derivatives. 10,11 In an attempt to rationalize the effects of cyclam configuration and to produce new specific antagonists for CXCR4, we have successfully synthesized a configurationally fixed bismacrocyclic compound and its zinc(II) complex. The solution and solid-state properties of the zinc(II) complex were investigated via high field NMR (800 MHz) and X-ray crystallography. The inhibitory effect on infection by HIV-1 and HIV-2 in MT-4 cells is also presented for both the chelator, 4 ((5-5′-[1,4-phenylenebis(methylene)]-bis (1,5,8,12-tetraazabicyclo[10.2.2]hexadecane)), and the complex Zn 2 4(OAc) 4 .There are six possible configurations that a cyclam ring can adopt on complexation to a metal ion, as defined by Bosnich and co-workers and shown in Figure 1b, where trans-III is generally the most thermodyn...

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Structural flexibility is demonstrated for copper(ii) TETA complexes used as radiopharmaceutical components, and may account for their insufficient stability in vivo. The development of some reduced flexibility configurationally-restrained chelators is reported.

Non-covalent encapsulation is an attractive ap-ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. This includes synthetic details and characterization, binding constant and kinetic experiments, details of radiochemical yield determination, stability, MTT assays and SPECT imaging experiments.

BackgroundThe stromal cell derived factor (SDF)-1/chemokine receptor (CXCR)-4 signaling pathway plays a key role in lung cancer metastasis and is molecular target for therapy. In the present study we investigated whether interleukin (IL)-24 can inhibit the SDF-1/CXCR4 axis and suppress lung cancer cell migration and invasion in vitro. Further, the efficacy of IL-24 in combination with CXCR4 antagonists was investigated.MethodsHuman H1299, A549, H460 and HCC827 lung cancer cell lines were used in the present study. The H1299 lung cancer cell line was stably transfected with doxycycline-inducible plasmid expression vector carrying the human IL-24 cDNA and used in the present study to determine the inhibitory effects of IL-24 on SDF-1/CXCR4 axis. H1299 and A549 cell lines were used in transient transfection studies. The inhibitory effects of IL-24 on SDF1/CXCR4 and its downstream targets were analyzed by quantitative RT-PCR, western blot, luciferase reporter assay, flow cytometry and immunocytochemistry. Functional studies included cell migration and invasion assays.Principal FindingsEndogenous CXCR4 protein expression levels varied among the four human lung cancer cell lines. Doxycycline-induced IL-24 expression in the H1299-IL24 cell line resulted in reduced CXCR4 mRNA and protein expression. IL-24 post-transcriptionally regulated CXCR4 mRNA expression by decreasing the half-life of CXCR4 mRNA (>40%). Functional studies showed IL-24 inhibited tumor cell migration and invasion concomitant with reduction in CXCR4 and its downstream targets (pAKTS473, pmTORS2448, pPRAS40T246 and HIF-1α). Additionally, IL-24 inhibited tumor cell migration both in the presence and absence of the CXCR4 agonist, SDF-1. Finally, IL-24 when combined with CXCR4 inhibitors (AMD3100, SJA5) or with CXCR4 siRNA demonstrated enhanced inhibitory activity on tumor cell migration.ConclusionsIL-24 disrupts the SDF-1/CXCR4 signaling pathway and inhibits lung tumor cell migration and invasion. Additionally, IL-24, when combined with CXCR4 inhibitors exhibited enhanced anti-metastatic activity and is an attractive therapeutic strategy for lung metastasis.

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