THE ACTIVITY AND EXPRESSION OF THYMIDINE PHOSPHORYLASE IN HUMAN SOLIDTUMORS

Thymidine phosphorylase (dThdPase) is identical to platelet-derived en dothelial cell growth factor (PD-ECGF) and has angiogenic activity. Si nce dThdPase seems to have an important role in angiogenesis of tumour s, we measured the activity and expression of dThdPase in various tumo urs and the adjacent non-neoplastic tissues. We assayed dThdPase activ ity by spectrophotometric means, and the expression of dThdPase was ex amined by immunoblotting and by immunohistochemical staining using a m onoclonal antibody against dThdPase. In the oesophagus, stomach, color ectum, pancreas, and lung, dThdPase activity in carcinomas was signifi cantly higher (P < 0.05) than that in the adjacent non-neoplastic tiss ues. The expression level of dThdPase detected by immunoblotting corre lated well with the activity of dThdPase. In the oesophagus, stomach, colorectum, gall bladder, pancreas and lung, the proportion of dThdPas e-positive tumours was significantly higher (P < 0.05 or 0.01) than th at of the dThdPase-positive adjacent normal tissues. In oesophageal, g astric, colorectal and lung carcinomas, the proportion of dThdPase pos itivity in advanced carcinomas was significantly higher (P < 0.01) tha n that in early carcinomas. Tumour-infiltrative macrophages or lymphoc ytes in the lymph node, alveolar macrophages and Kupffer cells express ed high levels of dThdPase. The results indicate that dThdPase activit y and expression level in many tumours are higher than those in the ad jacent non-neoplastic tissues, and that dThdPase may have an important role in the proliferation of these solid tumours. Copyright (C) 1996 Elsevier Science Ltd.