Lasso peptide microcin J25 variant containing RGD motif as a PET probe for integrin a v ß 3 in tumor imaging

Microcin J25 (MccJ25), a lasso peptide, has a unique 3-D interlocked structure that provides high stability under acidic conditions, at high temperatures, and in the presence of proteases. In this study, we generated a positron emission tomography (PET) probe based on MccJ25 analog with an RGD motif and investigated their pharmacokinetics and utility for integrin αvβ3 imaging in tumors. The MccJ25 variant with an RGD motif in the loop region and a lysine substitution at the C-terminus (MccJ25(RGDF)GtoK) was produced in E. coli transfected with plasmid DNA containing the MccJ25 biosynthetic gene cluster (mcjABCD). [64Cu]Cu-MccJ25(RGDF)GtoK was synthesized using the C-terminal lysine labeled with copper-64 (t1/2 = 12.7 h) via a bifunctional chelator; it showed stability in 90% mouse plasma for 45 min. Using PET imaging for integrin αvβ3 positive U87MG tumor bearing mice, [64Cu]Cu-MccJ25(RGDF)GtoK could clearly distinguish the tumor, and its accumulation was significantly higher than that of MccJ25(GIGT)GtoK without the binding motif for integrin αvβ3. Furthermore, MccJ25(RGDF)GtoK enabled visualization of only U87MG tumors but not MCF-7 tumors with low integrin αvβ3 expression in double tumor-bearing mice. In ex vivo biodistribution analysis, the integrin αvβ3 non-specific accumulation of [64Cu]Cu-MccJ25(RGDF)GtoK was significantly lower in various tissues, except for the kidneys, as compared to the control probe ([64Cu]Cu-cyclic RGD peptide). These results of the present study indicate that 64Cu-labeling methods are appropriate for the synthesis of MccJ25-based PET probes, and [64Cu]Cu-MccJ25 variants are useful tools for cancer molecular imaging

Macrocyclic peptide-based inhibition and imaging of hepatocyte growth factor.

金沢大学がん進展制御研究所Activation of hepatocyte growth factor (HGF) by proteolytic processing is triggered in cancer microenvironments, and subsequent signaling through the MET receptor is involved in cancer progression. However, the structure of HGF remains elusive, and few small/medium-sized molecules can modulate HGF. Here, we identified HiP-8, a macrocyclic peptide consisting of 12 amino acids, which selectively recognizes active HGF. Biochemical analysis and real-time single-molecule imaging by high-speed atomic force microscopy demonstrated that HiP-8 restricted the dynamic domains of HGF into static closed conformations, resulting in allosteric inhibition. Positron emission tomography using HiP-8 as a radiotracer enabled noninvasive visualization and simultaneous inhibition of HGF–MET activation status in tumors in a mouse model. Our results illustrate the conformational change in proteolytic activation of HGF and its detection and inhibition by a macrocyclic peptide, which may be useful for diagnosis and treatment of cancers.Embargo Period 6 month

Cyclic Trinuclear Rh₂M Complexes (M = Rh, Pt, Pd, Ni) Supported by <i>meso</i>-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane

Reaction of [MCl₂(cod)] (M = Pd, Pt) with a tetraphosphine, <i>meso</i>-1,3-bis­[(diphenylphosphinomethyl)­phenylphosphino]­propane (dpmppp), afforded the mononuclear complexes [MCl₂(dpmppp)] (M = Pd (<b>3a</b>), Pt (<b>3b</b>)), in which the dpmppp ligand coordinated to the M ion by two inner phosphorus atoms to form a six-membered chelate ring with two outer phosphines uncoordinated. The pendant outer phosphines readily reacted with [RhCl­(CO)₂]₂ to give the cationic heterotrinuclear complexes [MRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­X (X = [RhCl₂(CO)₂], M = Pd (<b>4a</b>), Pt (<b>4b</b>); X = PF₆, M = Pd (<b>5a</b>), Pt (<b>5b</b>)). The nickel analogue [NiRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­PF₆ (<b>5c</b>) was also prepared. A neutral homotrinuclear Rh₃ complex, [Rh₃(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>6</b>), was synthesized by the reaction of [RhCl­(CO)₂]₂ with dpmppp and was further reacted with HgX₂ (X = Cl, Br, I) to afford the Rh₃Hg tetranuclear complexes [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(CO)₂]­PF₆ (X = Cl (<b>7a</b>), Br (<b>7b</b>), I (<b>7c</b>)), where the Rh₃(μ-Cl)₂(μ-X) cores act as tridentate ligands to form three donor–acceptor Rh→Hg interactions. The two CO ligands of <b>7a</b>–<b>c</b> were replaced by XylNC to yield [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(XylNC)₂]­PF₆ (X = Cl (<b>8a</b>), Br (<b>8b</b>), I (<b>8c</b>)). The isocyanides had an appreciable influence on the three Rh→Hg interactions, which was monitored by the ²<i>J</i>_HgP values observed in the ³¹P­{¹H} NMR spectra and discussed on the basis of DFT calculations. Complex <b>6</b> also reacted with CuCl and HBF₄ to give [Rh₃(CuCl)­(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>9</b>) and [Rh₃(μ₃-H)­(μ-Cl)₃(μ-dpmppp)­(CO)₂]­BF₄ (<b>10</b>), respectively. These results suggested that the new tetraphosphine dpmppm proved quite useful in constructing fine-tunable heterometallic frameworks

Cyclic Trinuclear Rh₂M Complexes (M = Rh, Pt, Pd, Ni) Supported by <i>meso</i>-1,3-Bis[(diphenylphosphinomethyl)phenylphosphino]propane

Reaction of [MCl₂(cod)] (M = Pd, Pt) with a tetraphosphine, <i>meso</i>-1,3-bis­[(diphenylphosphinomethyl)­phenylphosphino]­propane (dpmppp), afforded the mononuclear complexes [MCl₂(dpmppp)] (M = Pd (<b>3a</b>), Pt (<b>3b</b>)), in which the dpmppp ligand coordinated to the M ion by two inner phosphorus atoms to form a six-membered chelate ring with two outer phosphines uncoordinated. The pendant outer phosphines readily reacted with [RhCl­(CO)₂]₂ to give the cationic heterotrinuclear complexes [MRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­X (X = [RhCl₂(CO)₂], M = Pd (<b>4a</b>), Pt (<b>4b</b>); X = PF₆, M = Pd (<b>5a</b>), Pt (<b>5b</b>)). The nickel analogue [NiRh₂(μ-Cl)₃(μ-dpmppp)­(CO)₂]­PF₆ (<b>5c</b>) was also prepared. A neutral homotrinuclear Rh₃ complex, [Rh₃(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>6</b>), was synthesized by the reaction of [RhCl­(CO)₂]₂ with dpmppp and was further reacted with HgX₂ (X = Cl, Br, I) to afford the Rh₃Hg tetranuclear complexes [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(CO)₂]­PF₆ (X = Cl (<b>7a</b>), Br (<b>7b</b>), I (<b>7c</b>)), where the Rh₃(μ-Cl)₂(μ-X) cores act as tridentate ligands to form three donor–acceptor Rh→Hg interactions. The two CO ligands of <b>7a</b>–<b>c</b> were replaced by XylNC to yield [Rh₃(HgX)­(μ-Cl)₂(μ-X)­(μ-dpmppp)­(XylNC)₂]­PF₆ (X = Cl (<b>8a</b>), Br (<b>8b</b>), I (<b>8c</b>)). The isocyanides had an appreciable influence on the three Rh→Hg interactions, which was monitored by the ²<i>J</i>_HgP values observed in the ³¹P­{¹H} NMR spectra and discussed on the basis of DFT calculations. Complex <b>6</b> also reacted with CuCl and HBF₄ to give [Rh₃(CuCl)­(μ-Cl)₃(μ-dpmppp)­(CO)₂] (<b>9</b>) and [Rh₃(μ₃-H)­(μ-Cl)₃(μ-dpmppp)­(CO)₂]­BF₄ (<b>10</b>), respectively. These results suggested that the new tetraphosphine dpmppm proved quite useful in constructing fine-tunable heterometallic frameworks