The excretion of β-aminoisobutyric acid, a thymine catabolite, was investigated in 46 patients with cancer. The dual origin of β-aminoisobutyric acid, indicating both transfer RNA-thymine and DNA-thymine as precursors, has been studied. Comparison of β-aminoisobutyric acid excretion with that of pseudouridine revealed a positive correlation of β-aminoisobutyric acid to pseudouridine excretion in 68% of the patients. Another group of the patients (24%) showed an excretion pattern constituting an increased excretion of pseudouridine and a normal β-aminoisobutyric acid excretion. Furthermore, it was possible to distinguish the probable genetic high excretors of β-aminoisobutyric acid who have an elevated β-aminoisobutyric acid excretion related to a normal pseudouridine and urate. This excretion pattern was the same in different clinical states. The excretion of urate was often found to parallel that of pseudouridine. However, in most cases the urate excretion was within the normal range. In addition, the excretion patterns following major surgery are illustrated. These showed a parallel increase in β-aminoisobutyric acid and pseudouridine on the 2nd and 3rd postoperative days and in pseudouridine alone on the 6th to 9th postoperative days. The results indicate a positive correlation of urinary β-aminoisobutyric acid to transfer RNA turnover in cancer patients.

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This investigation was supported by grants from the Danish Cancer Society and the Danish Medical Research Council j. nr. 512-2115 and -2125.

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