title: New soft alkylating agents with enhanced cytotoxicity against cancer cells resistant to chemotherapeutics and hypoxia.
abstract: Chloroethylureas (CEU) are soft alkylating agents that covalently bind to beta-tubulin (betaTAC) and affect microtubule polymerization dynamics. Herein, we report the identification of a CEU subset and its corresponding oxazolines, which induce cell growth inhibition, apoptosis, and microtubule disruption without alkylating beta-tubulin (N-betaTAC). Both betaTAC and N-betaTAC trigger the collapse of mitochondrial potential (DeltaPsi(m)) and modulate reactive oxygen species levels, following activation of intrinsic caspase-8 and caspase-9. Experiments using human fibrosarcoma HT1080 respiratory-deficient cells (rho(0)) and uncoupler of the mitochondrial respiratory chain (MRC) showed that betaTAC and N-betaTAC impaired the MRC. rho(0) cells displayed an increased sensitivity toward N-betaTAC as compared with rho(+) cells but, in contrast, were resistant to betaTAC or classic chemotherapeutics, such as paclitaxel. Oxazoline-195 (OXA-195), an N-betaTAC derivative, triggered massive swelling of isolated mitochondria. This effect was insensitive to cyclosporin A and to Bcl-2 addition. In contrast, adenine nucleotide translocator (ANT) antagonists, bongkrekic acid or atractyloside, diminished swelling induced by OXA-195. The antiproliferative activities of the N-betaTACs CEU-025 and OXA-152 were markedly decreased in the presence of atractyloside. Conversely, pretreatment with cyclosporin A enhanced growth inhibition induced by betaTAC and N-betaTAC. One of the proteins alkylated by N-betaTAC was identified as the voltage-dependent anion channel isoform-1, an ANT partner. Our results suggest that betaTAC and N-betaTAC, despite their common ability to affect the microtubule network, trigger different cytotoxic mechanisms in cancer cells. The role of mitochondria in these mechanisms and the potential of N-betaTAC as a new therapeutic approach for targeting hypoxia-resistant cells are discussed.
authors.affiliation: Unité de Biotechnologie et de Bioingénierie, CHUQ, Hôpital Saint-François d'Assise, Université Laval, Québec, Canada. alexandre.patenaude@crchul.ulaval.ca
authors.forename: Alexandre
authors.initials: A
authors.lastname: Patenaude
authors.forename: Réna G
authors.initials: RG
authors.lastname: Deschesnes
authors.forename: Jean L C
authors.initials: JL
authors.lastname: Rousseau
authors.forename: Eric
authors.initials: E
authors.lastname: Petitclerc
authors.forename: Jacques
authors.initials: J
authors.lastname: Lacroix
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Côté
authors.forename: René
authors.initials: R
authors.lastname: C-Gaudreault
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry / Q000627:therapeutic use*; D016466:CHO Cells; D015687:Cell Hypoxia; D006224:Cricetinae; D003412:Cricetulus; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004354:Drug Screening Assays, Antitumor; D004579:Electron Transport / Q000187:drug effects; D019073:HT29 Cells; D006801:Humans; D008870:Microtubules / Q000187:drug effects; D008954:Models, Biological; D009369:Neoplasms / Q000188:drug therapy*; D010671:Phenylurea Compounds / Q000627:therapeutic use*; D014404:Tubulin / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D018906:Antineoplastic Agents, Alkylating; D010671:Phenylurea Compounds; D014404:Tubulin