Correlation of biochemical effects and incorporation of 3-deazaguanine into nucleic acids to cytotoxicity in L1210 cells.

3-Deazaguanine, a tumor-inhibitory purine antimetabolite, is cytotoxic to L1210 leukemic cells in culture. The log percentage of viability correlated strongly (r2 = 0.986) with the product of the concentration of 3-deazaguanine, or [3-deazaguanine], and period of exposure (t) when [3-deazaguanine] was between 3 and 50 microM, and t was 12 or 24 h. We wished to relate this cytotoxicity to biochemical effects mediated by 3-deazaguanine. 3-Deazaguanine inhibited both DNA and protein synthesis, and both log DNA synthesis and log protein synthesis correlated inversely with [3-deazaguanine] X t and directly with cell viability (P less than 0.001). L1210 cells accumulated 3-deazaguanine 5'-triphosphate to a level of 1.5 nmol/10(6) cells. 3-Deazaguanine treatment had no effect on intracellular cytidine 5'-triphosphate levels, but reduced adenosine 5'-triphosphate and uridine 5'-triphosphate levels by 40% relative to control and guanosine 5'-triphosphate levels by 85% relative to control at a [3-deazaguanine] X t value at which 3-deazaguanine 5'-triphosphate accumulation was near maximal. Incorporation of 2-14C-labeled 3-deazaguanine into DNA and RNA, separated by Cs2SO4 density gradient centrifugation, was demonstrated. Incorporation into DNA was linear versus [3-deazaguanine] X t and correlated inversely with cell viability (P less than 0.001). These data suggest that 3-deazaguanine is anabolized and incorporated into DNA, and that this incorporation is related to decreased DNA synthesis and cell death. The decrease in protein synthesis and diminution of guanosine 5'-triphosphate levels following drug treatment may also contribute to the growth-inhibitory actions of 3-deazaguanine.