title: Mitomycin resistance in mammalian cells expressing the bacterial mitomycin C resistance protein MCRA.
abstract: The mitomycin C-resistance gene, mcrA, of Streptomyces lavendulae produces MCRA, a protein that protects this microorganism from its own antibiotic, the antitumor drug mitomycin C. Expression of the bacterial mcrA gene in mammalian Chinese hamster ovary cells causes profound resistance to mitomycin C and to its structurally related analog porfiromycin under aerobic conditions but produces little change in drug sensitivity under hypoxia. The mitomycins are prodrugs that are enzymatically reduced and activated intracellularly, producing cytotoxic semiquinone anion radical and hydroquinone reduction intermediates. In vitro, MCRA protects DNA from cross-linking by the hydroquinone reduction intermediate of these mitomycins by oxidizing the hydroquinone back to the parent molecule; thus, MCRA acts as a hydroquinone oxidase. These findings suggest potential therapeutic applications for MCRA in the treatment of cancer with the mitomycins and imply that intrinsic or selected mitomycin C resistance in mammalian cells may not be due solely to decreased bioactivation, as has been hypothesized previously, but instead could involve an MCRA-like mechanism.
authors.affiliation: Department of Pharmacology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Belcourt
authors.forename: P G
authors.initials: PG
authors.lastname: Penketh
authors.forename: W F
authors.initials: WF
authors.lastname: Hodnick
authors.forename: D A
authors.initials: DA
authors.lastname: Johnson
authors.forename: D H
authors.initials: DH
authors.lastname: Sherman
authors.forename: S
authors.initials: S
authors.lastname: Rockwell
authors.forename: A C
authors.initials: AC
authors.lastname: Sartorelli
mesh_terms: D000332:Aerobiosis; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001711:Biotransformation; D016466:CHO Cells; D015687:Cell Hypoxia; D002470:Cell Survival / Q000187:drug effects; D003001:Cloning, Molecular; D006224:Cricetinae; D004351:Drug Resistance; D016685:Mitomycin / Q000493:pharmacokinetics / Q000494:pharmacology*; D010088:Oxidoreductases; D011160:Porfiromycin / Q000494:pharmacology; D011355:Prodrugs / Q000493:pharmacokinetics / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D013302:Streptomyces / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D014162:Transfection
chemical_list: D001426:Bacterial Proteins; D011355:Prodrugs; D011994:Recombinant Proteins; D016685:Mitomycin; D010088:Oxidoreductases; C088145:mcrA protein, Streptomyces lavendulae; D011160:Porfiromycin