Serum pseudouridine as a biochemical marker in small cell lung cancer.

The serum level of pseudouridine, primarily a degradation product of tRNA, was determined by high-performance liquid chromatography in 24 patients with small cell lung cancer (SCLC), 13 patients with non-SCLC with advanced stages, 15 patients with pulmonary infectious diseases, and 18 healthy controls. The mean serum pseudouridine concentration was significantly higher in the patients with SCLC [4.75 +/- 1.76 (SD) nmol/ml] than that in the patients with pulmonary infectious diseases (3.39 +/- 1.38 nmol/ml) or in healthy controls (2.21 +/- 0.78 nmol/ml). The mean serum pseudouridine concentration in the patients with non-SCLC (4.07 +/- 0.95 nmol/ml) was significantly higher than that in healthy controls but not statistically different from that in the patients with pulmonary infectious diseases. The serum pseudouridine level was elevated above the mean value plus 2 SD for the healthy subjects (3.77 nmol/ml) in 66.7% of all patients with SCLC including 3 of 8 (37.5%) with limited disease and 13 of 16 (81.3%) with extensive disease, and 53.8% of the patients with non-SCLC. Serum carcinoembryonic antigen was elevated (greater than 5 ng/ml) in 29.2% and serum neuron-specific enolase (greater than 10 ng/ml) in 58.3% of the cases with SCLC. In the patients with SCLC followed up during chemotherapy, serum pseudouridine levels changed considerably parallel with the changes in the clinical response. These findings indicate that serum pseudouridine may be a useful biochemical marker in the patients with SCLC.