title: BCNU is a caspase-mediated inhibitor of drug-induced apoptosis.
abstract: BCNU [1,3-bis(2-chloroethyl)-1-nitrosourea], a bifunctional (alkylating/carbamoylating) anticancer agent, in noncytotoxic doses (12-50 microM) inhibited drug-induced apoptosis in HT58 human lymphoma cells exposed to etoposide (ETO; 50 microM) as well as in mouse thymocytes exposed to dexamethasone (5 microg/ml) in vitro in 4-h cultures. The cytoplasmic extracts of ETO-treated HT58 cells cleaved both purified poly(ADP-ribose)polymerase and Ac-Asp-Glu-Val-Asp-7-amino-4-methylcoumarin fluorogenic caspase substrate, indicating the presence of active caspases, and these effects were inhibited by BCNU concentration dependently. The carbamoylating decomposite, 2-chloroethyl-isocyanate (6-25 microM), also decreased ETO-induced apoptosis in HT58 cells in vitro and their caspase 3-like activity ex vivo, whereas N-(2-chloroethyl)-N-nitrosocarbamoyl-valinamide, an alkylating and mainly intramolecularly carbamoylating nitrosourea derivative (400 microM), did not influence these phenomena. Furthermore, the activity of recombinant caspase 3 was also strongly inhibited by BCNU and 2-chloroethyl-isocyanate. These results indicate that BCNU, via its carbamoylating capacity, can inactivate cysteine protease(s) essential for ETO-induced apoptosis. This apoptosis-modulating property of BCNU, in turn, may influence the efficacy of chemotherapeutic protocols in the treatment of cancer.
authors.affiliation: I. Institute of Pathology and Experimental Cancer Research, Semmelweis University of Medicine, Budapest, Hungary.
authors.forename: I
authors.initials: I
authors.lastname: Peták
authors.forename: R
authors.initials: R
authors.lastname: Mihalik
authors.forename: P I
authors.initials: PI
authors.lastname: Bauer
authors.forename: H
authors.initials: H
authors.lastname: Süli-Vargha
authors.forename: A
authors.initials: A
authors.lastname: Sebestyén
authors.forename: L
authors.initials: L
authors.lastname: Kopper
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002330:Carmustine / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D016393:Lymphoma, B-Cell; D014407:Tumor Cells, Cultured
chemical_list: D018906:Antineoplastic Agents, Alkylating; D005047:Etoposide; D003907:Dexamethasone; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D002330:Carmustine