Induction of cell death by combination treatment with cisplatin and 5-fluorouracil in a human oral squamous cell carcinoma cell line

The possible apoptosis-inducing activity of several sequential treatments of cisplatin (CDDP) and 5-fluorouracil (5-FU) against the human oral squamous cell carcinoma HSC-2 cell line was investigated. The following three combination treatments (CT) were used: simultaneous treatment with CDDP and 5-FU (for 72 hours) (CT-1), CDDP treatment (24 hours) followed by 5-FU treatment (48 hours) (CT-2) and 5-FU treatment (24 hours) followed by CDDP treatment (48 hours) (CT-3). CT-1 produced the highest cytotoxicity, followed by CT-3 and CT-2. No treatment induced any detectable internucleosomal DNA fragmentation, and caspase-3,-8 and -9 were activated to a much lesser extent than that attained using actinomycin D. High-performance liquid chromatography analysis demonstrated that 5-FU, as well as CT-1 and CT-2, preferentially reduced the intracellular concentration of putrescine. These results suggest that simultaneous treatment with CDDP and 5-FU induces lower level of apoptotic cell death in HSC-2 cells.