Studies on the effects of site-specifically located mitomycin C-DNA adducts in Escherichia coli

Date of Completion

January 1998

Keywords

Biology, Microbiology|Chemistry, Biochemistry|Chemistry, Pharmaceutical

Degree

Ph.D.

Abstract

Mitomycin C is an anticancer antibiotic widely used in clinical cancer chemotherapy, especially in the cancers of the breast, and prostate, and of superficial bladder cancer. As like other antitumor agents and chemical carcinogens, it acts by binding to DNA, forming covalent adducts. The chemistry of adduction of mitomycin C has been studied in detail, but this alone could not explain the mechanism of the antitumor effect of the drug. The study presented herein, therefore, investigated the effects of site-specifically located DNA adducts formed by mitomycin C in Escherichia coli. The response triggered by these compounds were evaluated, and the relationship between the structures and the cytotoxicity that they may cause were addressed.^ Using recombinant DNA techniques, a single DNA adduct, a mitomycin C monoadduct, mitomycin C cross-link, or a 2,7-diaminomitosene monoadduct, was incorporated into an M13 bacteriophage genome at a preselected site. The genomes constructed were fully characterized by DNA sequencing and enzyme digestion reactions. They were then transfected into various strains of E. coli, and the cytotoxicity and/or mutagenicity were scored. The mitomycin C monoadduct, the major covalent adduct formed, was found to be cytotoxic but not mutagenic (Ramos et al., 1998). The mitomycin C cross-link was highly toxic, in accordance with other cross-linking agents. The repair of this DNA lesion seem to involve a system that does not involve the recA gene, but is influenced by the polA gene. The 2,7-diaminomitosene adduct was less cytotoxic and not mutagenic in E. coli. ^

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