Excretion of modified nucleosides during development of malignant lymphomas in mice after whole body irradiation.

During x-ray-induced development of malignant lymphomas in mice their urinary excretion of eight modified nucleosides was monitored and the values were compared to the results of the histological examination of the animals at time of their sacrifice. It was found that the pathologically augmented excretion of modified nucleosides begins as much as several weeks before the malignant lymphomas can be diagnosed clinically. Thus some mice had increased levels of modified nucleosides even 10 weeks before sacrifice, though at the time of sacrifice the histological investigation revealed only some small foci of reticulum cell neoplasm in their spleen. It is therefore stressed that the usefulness of the determination of urinary modified nucleosides as an early noninvasive screening test for cancer in man and as an in vivo carcinogenicity test should be evaluated.