Objective: Thymidine phosphorylase (TP) is one of the enzymes involved in the salvage pathways of nucleotide synthesis. The enzyme converts thymidine to thymine and 2'-deoxyribose-1-phosphate and can also metabolize the prodrug 5'-deoxy-5-fluorouridine (Furtulon) to 5-fluorouracil and 5'-deoxy-D-ribose-1-phosphate. The aim of this study was to determine whether Paclitaxel (Taxol) induces TP expression and whether increased TP expression is further sensitized to Furtulon, using a human ovarian carcinoma cell line.
Material and methods: KF 28, a single-cell clone of a human ovarian carcinoma cell line, was used. TP expression was assessed by RT-PCR and Western blot analysis. Cell growth was evaluated by MTT assay.
Results: The concentration of Taxol that inhibited the growth of cells to the level of 50% of the control growth was 4.65 +/- 0.35 nM. TP gene expression was significantly increased at 72 hours 1 nM Taxol exposure compared to the control by RT-PCR (p = 0.020). Western blot analysis confirmed that the TP protein level was elevated compared to the control at 72 hours 1 nM Taxol exposure. Cell growth did not significantly differ between the control and 72 hours 1 nM Taxol exposure groups (p = 0.917). After 48 hours treatment with Furtulon followed by 72 hours 1 nM Taxol exposure, cell growth was dose-dependently inhibited in Taxol-treated cells (p = 0.022), but not in non-Taxol-treated cells (p = 0.082).
Conclusion: Our results show that a low concentration of Taxol is a candidate for increasing TP expression in a human ovarian carcinoma cell line, and that cells with an elevated level of TP expression can be further sensitized to Furtulon. This information might be valuable in the development of new therapeutic interventions for epithelial ovarian cancer.