title: Re-directing an alkylating agent to mitochondria alters drug target and cell death mechanism.
abstract: We have successfully delivered a reactive alkylating agent, chlorambucil (Cbl), to the mitochondria of mammalian cells. Here, we characterize the mechanism of cell death for mitochondria-targeted chlorambucil (mt-Cbl) in vitro and assess its efficacy in a xenograft mouse model of leukemia. Using a ρ° cell model, we show that mt-Cbl toxicity is not dependent on mitochondrial DNA damage. We also illustrate that re-targeting Cbl to mitochondria results in a shift in the cell death mechanism from apoptosis to necrosis, and that this behavior is a general feature of mitochondria-targeted Cbl. Despite the change in cell death mechanisms, we show that mt-Cbl is still effective in vivo and has an improved pharmacokinetic profile compared to the parent drug. These findings illustrate that mitochondrial rerouting changes the site of action of Cbl and also alters the cell death mechanism drastically without compromising in vivo efficacy. Thus, mitochondrial delivery allows the exploitation of Cbl as a promiscuous mitochondrial protein inhibitor with promising therapeutic potential.
authors.affiliation: Department of Pharmaceutical Sciences, Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Rida
authors.initials: R
authors.lastname: Mourtada
authors.forename: Sonali B
authors.initials: SB
authors.lastname: Fonseca
authors.forename: Simon P
authors.initials: SP
authors.lastname: Wisnovsky
authors.forename: Mark P
authors.initials: MP
authors.lastname: Pereira
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wang
authors.forename: Rose
authors.initials: R
authors.lastname: Hurren
authors.forename: Jeremy
authors.initials: J
authors.lastname: Parfitt
authors.forename: Lesley
authors.initials: L
authors.lastname: Larsen
authors.forename: Robin A J
authors.initials: RA
authors.lastname: Smith
authors.forename: Michael P
authors.initials: MP
authors.lastname: Murphy
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Schimmer
authors.forename: Shana O
authors.initials: SO
authors.lastname: Kelley
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000138:chemical synthesis / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D057846:Cell-Penetrating Peptides / Q000737:chemistry*; D002699:Chlorambucil / Q000138:chemical synthesis / Q000494:pharmacology*; D003432:Cross-Linking Reagents / Q000737:chemistry; D004272:DNA, Mitochondrial; D016503:Drug Delivery Systems / Q000379:methods*; D006367:HeLa Cells; D006801:Humans; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009336:Necrosis / Q000473:pathology; D017382:Reactive Oxygen Species / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D018906:Antineoplastic Agents, Alkylating; D057846:Cell-Penetrating Peptides; D003432:Cross-Linking Reagents; D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D002699:Chlorambucil