[PyNPase activity in primary and metastatic colorectal cancer]

5'-Deoxy-5-fluorouridine (5'-DFUR) is converted to 5-FU by the enzyme of Pyrimidine nucleoside phosphorylase (PyNPase). Its efficacy for lung metastases from colorectal cancer is known. So we investigated PyNPase activity in primary and metastatic lesions of colorectal cancer patients. The results revealed that PyNPase activity (microgram 5-FU/mg protein/hour) (mean +/- SD) was 122.1 +/- 61.1 (n = 48) in primary lesions, 91.6 +/- 48.3 (n = 4) in lymph node metastases, 135.2 +/- 56.4 (n = 10) in liver metastases and 168.2 +/- 79.8 (n = 11) in lung metastases. In non-cancerous tissues adjacent to the cancer lesions, PyNPase activity was 51.5 +/- 18.8 in normal colorectal mucosa, 61.8 +/- 24.7 in normal liver and 43.0 +/- 21.2 in normal lung. These results demonstrated that PyNPase activity in the cancer lesions reached significantly higher levels than in the non-cancerous tissues (p < 0.01); and the T/N ratio of PyNPase activity in lung was also significantly higher than in primary or other metastatic lesions (p < 0.05). It was surmised that the clinical response of colorectal cancer to 5'-DFUR had been influenced by PyNPase activity.