title: Synthesis and characterization of Pt(IV) fluorescein conjugates to investigate Pt(IV) intracellular transformations.
abstract: Pt(IV) anticancer compounds typically operate as prodrugs that are reduced in the hypoxic environment of cancer cells, losing two axial ligands in the process to generate active Pt(II) species. Here we report the synthesis of two fluorescent Pt(IV) prodrugs of cisplatin in order to image and evaluate the Pt(IV) reduction process in simulated and real biological environments. Treatment of the complexes dissolved in PBS buffer with reducing agents typically encountered in cells, glutathione or ascorbate, afforded a 3- to 5-fold fluorescence turn-on owing to reduction and loss of their fluorescein-based axial ligands, which are quenched when bound to platinum. Both Pt(IV) conjugates displayed moderate cytotoxicity against human cancer cell lines, with IC50 values higher than that of cisplatin. Immunoblotting and DNA flow cytometry analyses of one of the complexes, Pt(IV)FL2, revealed that it damages DNA, causes cell cycle arrest in S or G2/M depending on exposure time, and ultimately triggers apoptotic cell death. Fluorescence microscopic studies prove that Pt(IV)FL2 enters cells intact and undergoes reduction intracellularly. The results are best interpreted in terms of a model in which the axial fluorescein ligands are expelled through lysosomes, with the platinum(II) moiety generated in the process binding to genomic DNA, which results in cell death.
authors: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors: Ying
authors: Y
authors: Song
authors: Kogularamanan
authors: K
authors: Suntharalingam
authors: Jessica S
authors: JS
authors: Yeung
authors: Maksim
authors: M
authors: Royzen
authors: Stephen J
authors: SJ
authors: Lippard
mesh_terms: D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D019793:Fluorescein / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy; D061848:Optical Imaging; D010084:Oxidation-Reduction; D011355:Prodrugs / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D011355:Prodrugs; D002945:Cisplatin; D019793:Fluorescein
references: J Am Chem Soc. 2007 Nov 7;129(44):13400-1
references: 17929931
references: ACS Chem Biol. 2008 Mar 20;3(3):142-55
references: 18355003
references: Inorg Chem. 2011 Apr 4;50(7):3103-15
references: 21361279
references: Angew Chem Int Ed Engl. 2013 Jun 3;52(23):6059-62
references: 23686723
references: J Biol Chem. 2007 May 25;282(21):15506-15
references: 17403685
references: Dalton Trans. 2010 Sep 21;39(35):8113-27
references: 20593091
references: Dalton Trans. 2009 Apr 28;(16):3092-101
references: 19352538
references: J Vet Intern Med. 2011 Jul-Aug;25(4):909-15
references: 21564292
references: Nat Rev Cancer. 2007 Aug;7(8):573-84
references: 17625587
references: J Inorg Biochem. 2004 Oct;98(10):1614-24
references: 15458824
references: J Am Chem Soc. 2008 Aug 27;130(34):11467-76
references: 18661990
references: Chem Rev. 2009 Oct;109(10):4911-20
references: 19711978
references: J Microsc. 1993 Mar;169(3):375-382
references: 33930978
references: Metallomics. 2012 Jun;4(6):568-75
references: 22569908
references: Oncogene. 2003 Oct 20;22(47):7265-79
references: 14576837
references: J Biol Inorg Chem. 2003 Sep;8(7):726-32
references: 12884089
references: Bioconjug Chem. 2008 Jan;19(1):39-49
references: 17845003
references: Nature. 2000 Oct 12;407(6805):770-6
references: 11048727
references: J Biol Chem. 1994 Apr 1;269(13):9397-400
references: 8144521
references: Chemistry. 2013 Jan 28;19(5):1672-6
references: 23255183
references: J Med Chem. 2007 Jul 26;50(15):3403-11
references: 17602547
references: FEBS J. 2007 Jan;274(1):1-22
references: 17222174
references: Biophys J. 1995 Oct;69(4):1569-83
references: 8534828
references: Inorganica Chim Acta. 2012 Jul 1;389:77-84
references: 22837584
references: Cancer Chemother Pharmacol. 2011 Jun;67(6):1247-56
references: 20697713
references: J Biol Chem. 2001 Nov 9;276(45):42462-7
references: 11571274
references: J Biol Chem. 1998 Mar 6;273(10):5858-68
references: 9488723
references: J Am Chem Soc. 2003 Jun 25;125(25):7524-5
references: 12812486