The expression of thymidine phosphorylase and thrombomodulin in human colorectal carcinomas

Thymidine phosphorylase (dThdPase) is an enzyme involved in pyrimidine nucleoside metabolism. dThdPase activity is increased in several types of malignant tumors. Recently, we demonstrated that dThdPase is identical to platelet-derived endothelial cell growth factor (PD-ECGF) and that dThdPase has angiogenic activity. We measured dThdPase activity and the level of thrombomodulin (TM) as a marker for endothelial cells in colorectal carcinomas and adjacent normal tissues from 21 patients, and in adenomas from 13 patients. The average dThdPase activity of colorectal carcinomas (11.58 ± 6.30 nmol/100 μg protein/h) was significantly higher than that of adenomas (8.57 ± 4.14 nmol/100 μg protein/h) or normal tissues (4.89 ± 3.16 nmol/100 μg protein/h). In immunohistochemical study, the expression of dThdPase was observed more frequently in colorectal carcinomas than in adenomas or normal mucosas. The amount of TM in colorectal carcinomas (8.32 ± 5.07 ng/100 μg protein) was significantly higher than that of adenomas (4.51 ± 4.49 ng/100 μg protein) or normal tissues (3.51 ±2.78 ng/100 μg protein). dThdPase activity in human colorectal carcinomas, adenomas and normal tissues was significantly correlated with the expression of TM in these tissues. These results indicate that the expression levels of both dThdPase and TM in colorectal carcinomas are higher than those in colorectal adenomas and normal tissues and suggest that dThdPase may be involved in angiogenesis in human colorectal carcinomas, adenomas and normal tissues.