MECHANISM OF ACTION OF BLEOMYCIN. STUDIES WITH THE GROWING CULTURE OF BACTERIAL AND TUMOR CELLS

Abstract

Bleomycin was observed to inhibit DNA and protein syntheses in intact Escherichia coli, Ehrlich carcinoma and HeLa cells. DNA synthesis was more profoundly affected than protein synthesis. RNA synthesis was not significantly suppressed by the antibiotic. The activity of bleomycin was highly dependent on the number of cells and on the concentration of phosphate in the medium, being more pronounced at low concentration of phosphate and with fewer cells. Bleomycin complex, copper-free bleomycin A₂, copper-chelating bleomycin A₂ (Cu 2.6 % w/w) and copper-saturated bleomycin A₂ (Cu 5.1 %) were studied. All of them exhibited substantially the same activity. Bleomycin caused elongation of E. coli cells and enlargement of HeLa cells, with a reduction in the number of mitotic figures of growing HeLa cells, indicating that the antibiotic interfered with the mitotic process.