INTERACTIONS OF MITOMYCIN-C WITH MAMMALIAN DNA DETECTED BY ALKALINE ELUTION

  • 1 January 1985
    • journal article
    • research article
    • Vol. 45  (8) , 3510-3516
Abstract
The antitumor antibiotic mitomycin C (MMC) was studied in vitro using L1210 leukemia [mouse] and 8226 human myeloma cells. Cytotoxicity was evaluated by colony formation in soft agar, and DNA damage was analyzed using alkaline elution filter assays. The purposes of these studies were: to characterize the time course of the MMC-DNA damage; to characterize the type of DNA damage [DNA-DNA interstrand cross-links (ISC), DNA-protein cross-links (DPC), single and double strand breaks (SSB, DSB)]; and to correlate this damage with cytotoxicity in vitro. Colony-forming assays showed the D0 [mean lethal dose] value for 1 h MMC to be 15.0 .mu.M for L1210 cells and 17 .mu.M for 8226 cells. Alkaline elution studies showed that dose-dependent ISC and DPC formed rapidly following MMC exposure. Removal of cross-links was delayed, with only 50% repaired 32 h after exposure. There was a good correlation between ISC and cytotoxicity in dose-response studies in each cell line. ISC appeared to comprise most of the MMC-DNA lesions in both cell lines. NO DNA SSB or DSB were observed following MMC exposure. Nuclei isolated from both cell lines and exposed to MMC produced less MMC alkylation than whole cells but, again, no strand breaks were evident. MMC is principally an alkylating agent when used at pharmacological (cytotoxic) concentrations in vitro. The lack of evidence for DNA strand breaks discounts a significant role for putative quinone-generated oxygen free radicals in the production of MMC cytotoxicity.