In Vitro Cytotoxic and Biochemical Effects of 5-Aza-2′-deoxycytidine

Summary

The in vitro effect of 5-aza-2′-deoxycytidine (5-aza-CdR) on cytotoxicity and macromolecular synthesis in A(T₁)C1-3 hamster fibrosarcoma cells was investigated. The in vitro concentrations that produce 50% cell kill for 5-aza-CdR were about 1.0 and 0.01 µg/ml for a 2- and 24-hr exposure, respectively. 5-aza-CdR inhibited the growth of the fibrosarcoma cells by 40% at a concentration of 0.05 µg/ml. Deoxycytidine, but not cytidine, was a potent antagonist of the cytotoxicity produced by 5-aza-CdR. At cytotoxic concentrations 5-aza-CdR did not appear to inhibit DNA, RNA, or protein synthesis during a 1-hr incubation as measured by the incorporation of radioactive thymidine, uridine, or leucine into acid-insoluble material. At a concentration of 10 µg/ml, 5-aza-CdR stimulated the incorporation of radioactive thymidine into DNA by more than 50%. These results indicate that 5-aza-CdR is a very potent cytotoxic agent to tumor cells in vitro at concentrations that do not inhibit macromolecular synthesis.