By means of a sensitive and specific method utilizing gas-liquid chromatography, the excretion levels for three nucleosides, degradation minor base products of ribonucleic acid, primarily transfer ribonucleic acid, were determined i n 24hour urine specimens from over 200 patients with solid tumor malignancies.
These nucleosides were N*,Nz-dimethylguanosine, I-methylinosine, a n d pseudouridine. When compared to normal control values, elevated levels of these compounds were found for patients i n each of several tumor types studied. Increases i n pseudouridine excretion suggest increased tumor transfer ribonucleic acid turnover; in addition, for the methylated nucleosides, higher t h a n normal values may reflect enhanced transfer ribonucleic acid methylase activity of the neoplastic cells.
Cancer 36:3!%398, 1975.
HE lMPORTANT ROLE OF TRANSFER RIBO-
T nucleic acid (tRNA) in the synthesis of protein lends added importance to the possible impact alterations in its macromolecular structure may have on its function. T h e modification of tRNA at the enzymatic level has been studied extensively, indicating increased activity and capacity of specific tRNA methylases are characteristic of neoplastic cells.8-21. 24-3e,38-41,43 In a recent summary, Borek7 reported that abnormally high tRNA methylase capacity had been found in 30 different malignant tumors, compared to their corresponding normal tissues. In 1962, Bergquist and Mathews' first reported elevated amounts of methylated tRNA nucleic acid bases in specific animal tumors in comparison, to their normal tissue counterparts, and in 1967 Viali et al.42 found increased methylated bases in tRNAs of human brain tumors.
Summarizing available published data, Borek' noted elevated levels for methylated bases had been found in the tRNAs of 12 different tumors, both animal and human. Included as minor constituents combined in the intact macromolecule are methylated derivatives and pseudouridine (Y) in addition to other substituted bases. These minor bases