title: Identification of the structural determinants for anticancer activity of a ruthenium arene peptide conjugate.
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 [Leu(5)]-enkephalin. [Chlorido(η(6)-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=η(6)-p-cymene) moiety to the peptide involved N-terminal modification of an alkyne-[Leu(5)]-enkephalin with a 2-(azidomethyl)-5-hydroxy-4H-pyran-4-one linker, using Cu(I)-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 (η(6)-p-cymene)ruthenium(II)] (5) and [chlorido(η(6)-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.
authors.affiliation: Institute of Inorganic Chemistry, University of Vienna, Waehringer Strasse 42, 1090 Vienna, Austria.
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Meier
authors.forename: Maria
authors.initials: M
authors.lastname: Novak
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kandioller
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jakupec
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Arion
authors.forename: Nils
authors.initials: N
authors.lastname: Metzler-Nolte
authors.forename: Bernhard K
authors.initials: BK
authors.lastname: Keppler
authors.forename: Christian G
authors.initials: CG
authors.lastname: Hartinger
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D045744:Cell Line, Tumor; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D018360:Crystallography, X-Ray; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D008024:Ligands; D039821:Monoterpenes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011753:Pyrones / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D012428:Ruthenium; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014230:Triazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D056831:Coordination Complexes; D008024:Ligands; D039821:Monoterpenes; D009842:Oligopeptides; D011753:Pyrones; D014230:Triazoles; D012428:Ruthenium
keywords: antitumor agents; bioorganometallic chemistry; mass spectrometry; peptide bioconjugates; ruthenium complexes