Thymidylate synthase and dihydropyrimidine dehydrogenase activities in non-small cell lung cancer tissues: relationship with in vitro sensitivity to 5-fluorouracil.

We examined enzymatic activities of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) in non-small cell lung cancer (NSCLC) tissues to determine the relationship to tumor sensitivity to 5-fluorouracil (5-FU). TS and DPD activities were measured in 60 surgically resected primary NSCLC tissues using a TS-binding assay and a radioenzyme assay, respectively. In vitro tumor sensitivity to 5-FU was assayed using a collagen gel droplet embedded culture drug test (CD-DST). DPD activities slightly correlated with in vitro sensitivity to 5-FU (r=0.402,P=0.013), such that tumors with higher DPD activity were more resistant to 5-FU. In contrast, no correlation was observed in TS activities. Thus, it was suggested that only DPD activity in NSCLC tissues is a potential indicator in predicting tumor sensitivity to 5-FU. Based on these results, further study is needed to evaluate the clinical significance of these enzymes in 5-FU-based chemotherapy for patients with NSCLC.