Identification of the Structural Determinants for Anticancer Activity of a Ruthenium Arene Peptide Conjugate

Authors

  • Dr. Samuel M. Meier,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    2. Research Platform “Translational Cancer Therapy Research”, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Maria Novak,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Dr. Wolfgang Kandioller,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    2. Research Platform “Translational Cancer Therapy Research”, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Dr. Michael A. Jakupec,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    2. Research Platform “Translational Cancer Therapy Research”, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Prof. Dr. Vladimir B. Arion,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Prof. Dr. Nils Metzler-Nolte,

    1. Inorganic Chemistry I–Bioinorganic Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Universitätsstrasse 150, 48801 Bochum (Germany)
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  • Prof. Dr. Bernhard K. Keppler,

    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    2. Research Platform “Translational Cancer Therapy Research”, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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  • Prof. Dr. Christian G. Hartinger

    Corresponding author
    1. Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    2. Research Platform “Translational Cancer Therapy Research”, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
    3. School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142 (New Zealand)
    • Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna (Austria)
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Abstract

Organometallic Ru(arene)–peptide bioconjugates with potent in vitro anticancer activity are rare. We have prepared a conjugate of a Ru(arene) complex with the neuropeptide [Leu5]-enkephalin. [Chlorido(η6-p-cymene)(5-oxo-κO-2-{(4-[(N-tyrosinyl-glycinyl-glycinyl-phenylalanyl-leucinyl-NH2)propanamido]-1H-1,2,3-triazol-1-yl)methyl}-4H-pyronato-κO)ruthenium(II)] (8) shows antiproliferative activity in human ovarian carcinoma cells with an IC50 value as low as 13 μM, whereas the peptide or the Ru moiety alone are hardly cytotoxic. The conjugation strategy for linking the Ru(cym) (cym=η6-p-cymene) moiety to the peptide involved N-terminal modification of an alkyne-[Leu5]-enkephalin with a 2-(azidomethyl)-5-hydroxy-4H-pyran-4-one linker, using CuI-catalyzed alkyne–azide cycloaddition (CuAAC), and subsequent metallation with the Ru(cym) moiety. The ruthenium-bioconjugate was characterized by high resolution top-down electrospray ionization mass spectrometry (ESI-MS) with regard to peptide sequence, linker modification and metallation site. Notably, complete sequence coverage was obtained and the Ru(cym) moiety was confirmed to be coordinated to the pyronato linker. The ruthenium-bioconjugate was analyzed with respect to cytotoxicity-determining constituents, and through the bioconjugate models [{2-(azidomethyl)-5-oxo-κO-4H-pyronato-κO}chloride (η6-p-cymene)ruthenium(II)] (5) and [chlorido(η6-p-cymene){5-oxo-κO-2-([(4-(phenoxymethyl)-1H-1,2,3-triazol-1-yl]methyl)-4H-pyronato-κO}ruthenium(II)] (6) the Ru(cym) fragment with a triazole-carrying pyronato ligand was identified as the minimal unit required to achieve in vitro anticancer activity.

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