ACTION OF 5-FLUOROCYCLOCYTIDINE ON CULTURED L-5178Y CELLS

Abstract

Effect of substitution of 5-position of cyclocytidine with fluorine on its antitumor activity in cultured cells was examined. 5-Fluorocyclocytidine was active against cultured L-5178Y cells similar to cyclocytidine. IC₅₀ of the compound was 0.054μg/ml. This compound inhibited thymidine incorporation into acid-insoluble fraction of the cells. Cell growth inhibition by 5-fluorocyclocytidine was reversed by deoxycytidine but not by thymidine and deoxyuridine. On the other hand, cell growth inhibition by 5-fluorouracil was reversed by thymidine and deoxyuridine. As a result, site of action of 5-fluorocyclocytidine was considered to be similar to that of cyclocytidine and not to 5-fluorouracil.