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Inhibition of the Synthesis of Polyamines and DNA in Activated Lymphocytes by a Combination of -Methylornithine and Methylglyoxal Bis(guanylhydrazone)¹

Department of Biochemistry, SJ-70, University of Washington, Seattle, Washington 98195

The cancer chemotherapeutic drug, methylglyoxal bis(guanylhydrazone), inhibits the synthesis of spermidine and spermine, but allows continued putrescine production in small lymphocytes stimulated by concanavalin A. DNA replication in these cells is inhibited 50% while the synthesis of protein and RNA continues normally. When excess putrescine accumulation in the presence of methylglyoxal bis(guanylhydrazone) was inhibited with -methylornithine, a competitive inhibitor of ornithine decarboxylase, the inhibition of DNA replication was accentuated, with still no effect on protein or RNA synthesis. No inhibition of DNA synthesis by the combination of -methylornithine and methylglyoxal bis(guanylhydrazone) was observed when the inhibitors were added after accumulation of cellular polyamines. In addition, inhibition was reversed by exogenous putrescine, spermidine, or spermine. We conclude that putrescine can fulfill in part the role normally played by spermidine and spermine in DNA replication, and that blocking putrescine synthesis in the presence of methylglyoxal bis(guanylhydrazone) amplifies the polyamine requirement. The implications of this with regard to polyamine synthesis as a site of chemotherapy are discussed.

¹ Supported in part by Grant BMS 75-05381 from the National Science Foundation, Grant NP195 from the American Cancer Society, and Grant GM 13957 from NIH.

Received 11/15/76. Accepted 6/ 8/77.