Inhibition of DNA synthesis and chromosome aberrations in cultured Ehrlich ascites tumor cells following treatment with luteoskyrin

Abstract

The effect of the hepatotoxic and tumorigenic bis-polyhydroxydihydroanthraquinone luteoskyrin on nucleic acid and protein metabolism was studied in asynchronous cultures of Ehrlich ascites tumor cells. Exposure to luteoskyrin (1.0 μg/ml; 1.74 × 10 −6 M) resulted in a gradual inhibition of DNA synthesis and cell multiplication, although RNA and protein synthesis continued for some time after DNA synthesis was almost completely arrested. Pulse-labeling with 14C-2-thymidine, 14C-2-uridine and 14C-2-leucine in the presence of luteoskyrin revealed an exponential decline of the per cell rate (cpm/10 μg DNA) of DNA synthesis, while the per cell rates of RNA and protein synthesis were only partially inhibited over a period of 126 h; for example, after 73 h in the presence of luteoskyrin the per cell rate of DNA synthesis was inhibited by 93% whereas RNA and protein synthesis were inhibited only 48% and 40%, respectively. Luteoskyrin-treated cultures contain increased numbers of multinucleate cells, and cells which accumulate Sudan Black positive material. Luteoskyrin-resistant cells (growing in the presence of 1.0 μg/ml and at higher concentrations) were isolated by gradual adaptation to increasing concentrations of luteoskyrin. Abnormally long and partially “stretched” metaphase chromosomes were observed in these resistant cells after cultivation for 3–5 months in the presence of luteoskyrin (1.0 μg/ml). It is suggested that luteoskyrin exerts the described effects primarily by interference with the mechanisms of DNA replication.