Effect of vitamin A compounds on DNA biosynthesis in murine tumor models in vitro

The effect of vitamin A compounds on the DNA biosynthesis inhibition of murine ascites tumor models such as P388 lymphocytic leukemia, L1210 lymphoid leukemia, sarcoma 180 and Ehrlich ascites carcinoma was found to be concentration- and time-dependent. The results of the experiments carried out in vitro for 4 h measured by the extent of ³H-thymidine incorporation into the DNA of these tumor cells permit us to conclude that (a) at the given concentration and time, the metabolic role of vitamin A compounds influences the regulation of processes leading to DNA biosynthesis inhibition; (b) the effect of vitamin A is uniform irrespective of tumor cells heterogeneity; (c) vitamin A does not affect transport of thymidine, and (d) the dose-dependent increase in the inhibition of these tumor cells by vitamin A is characterized by undifferentiated morphology showing uniformity in the given tumor cell population associated with a total lack of differentiation.