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The effects of Mitomycin C on two mammalian cell lines, L-929 mouse fibroblast and S-91 mouse melanoma, have been investigated. Appropriate concentrations of the antibiotic caused the formation of giant cells, a large proportion of which showed nuclear fragmentation, DNA-containing droplets in the cytoplasm, and partial depolymerization of nuclear DNA. Electron microscopy of the DNA-containing bodies, which contain histones and are Feulgen positive, revealed them to be bounded by a double membrane indistinguishable from that surrounding the nucleus. Of a number of agents which inhibit growth by interfering with nucleic acid metabolism only Mitomycin produced these effects in a major proportion of the cells. A possibly related antibiotic, Actinomycin D, causes the disappearance of nucleoli and a loss of cellular RNA. |
