The role of thymidine phosphorylase expression in the invasiveness of gastric carcinoma.

BACKGROUND: Thymidine phosphorylase (TP) has angiogenic activity in various cancer tissues. Gastric carcinomas are classified into two histologic groups: differentiated and undifferentiated adenocarcinomas. There are differences in the modes of development and the extent of infiltration between the two groups. The purpose of the current study was to determine whether TP is involved in the invasiveness and progression of these two types of gastric carcinoma.
METHODS: To investigate the expression and localization of TP and the microvessel counts, the authors examined specimens from 149 gastric carcinoma patients. The specimens were stained using monoclonal antibody against TP and polyclonal antibody against factor VIII. To determine the cell type expressing TP, immunohistochemical staining using a monoclonal antibody against CD68 that is specific for macrophages and double staining using antibodies to both TP and CD68 were performed.
RESULTS: The proportion of TP positive tumors in differentiated adenocarcinomas was higher than that in undifferentiated adenocarcinomas. The TP positive differentiated adenocarcinomas invaded more deeply than the TP negative ones, but this was not the case with undifferentiated adenocarcinomas. TP was expressed mainly in the invasive edges of tumors and was expressed more frequently in macrophages than in tumor cells. TP expression was correlated with microvessel count and CD68 expression. Patients with TP positive carcinomas had a poorer prognosis than those with TP negative differentiated adenocarcinomas.
CONCLUSIONS: TP expressed in macrophages may be correlated with microvessel count and play an important role in tumor invasiveness and progression in differentiated gastric adenocarcinoma.