Increased expression of thymidine phosphorylase in tumor tissue in proportion to TP-expression in primary normal tissue

Thymidine phosphorylase (TP) is considered to be a key enzyme affecting the prognosis of patients with advanced gastrointestinal cancer. We tried to demonstrate the correlation of TP expression in tumor tissue and adjacent normal tissue, that is, primary normal tissue. The present study was designed to quantify TP level by enzyme-linked immunosorbent assay (ELISA) in tumor tissue and adjacent normal tissue obtained from 42 hepato-gastrointestinal cancer patients including 15 with gastric, 19 with colorectal and 8 with hepatocellular carcinomas. TP levels in tumor tissues were higher than those in adjacent normal tissues (P<0.001). There was a significant correlation between the expression of TP in tumor tissue and adjacent normal tissue (R=0.711, p<0.001; y=23.420+1.534x). On the other hand, there was no significant correlation between the ratio of tumor to adjacent normal tissue levels of TP (TP T/N) and expression of TP in tumor tissue (R=0.250, p=0.110). Thus, TP expression in tumor tissue may be high in proportion to TP expression in primary tissue. Furthermore, in clinical care, not only TP level in tumor tissue but also TP T/N value should be considered when using anticancer agents that become effective after conversion by TP to the active drug 5-FU.