Abstract
Knowledge of population thymidylate synthase (TS) levels in malignant tumors and normal tissues is essential for the use of TS as a predictor for 5-fluorouracil treatment. Tumor tissue TS levels in fresh frozen surgical biopsies from 136 patients with gastrointestinal or breast cancer, not previously subjected to chemotherapy, were analysed by [3H]FdUMP radioligand binding assay. TS levels were 2.4±0.31 pmo1/g in liver metastases of colorectal cancer (n=87), 4.2±1.0 pmo1/g in primary colorectal cancer (n=13), 2.7±0.93 pmo1/g in gastric cancer (n=13), 3.1±1.7 pmo1/g in pancreatic cancer (n=10), 3.4±1.4 pmo1/g in breast cancer (n=13) and 0.58±0.075 pmo1/g in normal liver parenchyma (n=24). TS levels were significantly higher in malignant tumor tissues compared to normal liver parenchyma.