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Modulation of Transfer RNA-methylating Enzyme Activities in Murine Leukemic Cells¹

Department of Pharmacology and Toxicology, Division of Oncology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642

The activities of those processing enzymes responsible for the methylation of tRNA in murine leukemic cells were compared in sublines selected for their sensitivity and resistance to various antineoplastic agents. With one exception, the capacity and extent of tRNA methylation were elevated in the drug-resistant sublines. The following order of activities was demonstrated: L1210/cytoxan > L1210/cytosine arabinoside > L1210; L5178Y/actinomycin D > L5178Y; L5178YF/L-asparaginase > L5178YF; but P388 > P388/vincristine. These results suggest that the methylation of tRNA in murine leukemic cells may be modulated in cells with drug-resistant properties.

¹ This investigation was supported by Grant CA-11198 from the National Cancer Institute, General Research Support Grant RR-05403 from the USPHS, Grant IN-18M from the American Cancer Society, and USPHS Grant CA-12269 from the National Cancer Institute.

Received 5/ 4/71. Accepted 2/25/72.