Effect of methoxy-p-benzoquinones and methoxy-p-hydroquinones on DNA synthesis in Ehrlich ascites tumor cells.

The effects of various methoxy-p-quinones and methoxy-p-hydroquinones on DNA synthesis and thymidine transport in Ehrlich Ascites Tumor Cells was investigated. The inhibitory concentrations (IC50) were in the range of 5 to 65 microM. Adriamycin, used as positive control, had an IC50 of 6 microM. 2,3-Dimethoxy-benzoquinone and -hydroquinone and 2,3,5,6-tetramethoxy-benzoquinone clearly inhibited DNA synthesis at concentrations where thymidine transport was not affected. 2-Methoxy-hydroquinone, 2-methoxy-benzoquinone, 2,6-dimethoxy-benzoquinone, 2,5-dimethoxy-benzoquinone had IC50-values close to the dose inhibiting also thymidine transport. 2,5-Dimethoxy-benzoquinone, 2,3,5-trimethoxy-hydroquinone, 2,3,5-trimethoxy-benzoquinone and 2,3,5,6-tetramethoxy-hydroquinone strongly inhibited thymidine transport without a significant effect on DNA synthesis. Addition of ascorbate enhanced the inhibitory activity of 2,6-dimethoxy-benzoquinone.