The urinary concentration of
pseudouridine, primarily a breakdown product of
tRNA, was determined by high-performance liquid chromatography in 33 patients with
small cell lung cancer (SCLC), 18 patients with
non-small cell lung cancer (NSCLC), 18 patients with benign
pulmonary diseases (eg, TB,
COPD), and 16 healthy controls. The mean urinary
pseudouridine concentration levels of the patients with SCLC, NSCLC, benign
pulmonary disease and the healthy controls were 22.7 +/- 11.8, 15.6 +/- 6.0, 13.4 +/- 3.6, 12.1 +/- 3.2 nmol/mumol
creatinine (mean +/- SD), respectively. The mean urinary
pseudouridine concentration was significantly higher in patients with SCLC than that in patients with NSCLC, benign
pulmonary disease and in the healthy controls. There was no significant difference in the urinary
pseudouridine levels of patients with NSCLC and healthy controls or patients with benign
pulmonary disease. Urinary
pseudouridine levels above 18.5 nmol/mumol
creatinine (mean value +/- 2SD for healthy controls) were noted in 54.5% of patients with SCLC, including 11 of 17 (64.7%) in extensive stage and seven of 16 (43.8%) in limited stage, and 27.8% of the patients with NSCLC. Of the 12 patients with SCLC who had follow-up urinary samples taken in series during
chemotherapy courses, there was considerable urinary
pseudouridine level change which paralleled the change in clinical response. Although urinary
pseudouridine is not a specific marker for SCLC, it represents the
tumor burden and reflects the clinical status. These findings indicate that urinary
pseudouridine may be a useful
tumor marker in patients with SCLC.