Effects of cisplatin, 5-fluorouracil, and radiation on cell cycle regulation and apoptosis in the hypopharyngeal carcinoma cell line

In head and neck cancer including hypopharyngeal cancer, cisplatin and 5-fluorouracil (5-FU) usually have been used as neoadjuvant chemotherapeutic agents. We investigated the effects of cisplatin, 5-FU and radiation on p53 protein expression and cell responses ( cell cycle arrest and/or apoptosis) in the hypopharyngeal carcinoma cell line (PNUH-12; mutant type p53). PNUH- 12 cells were treated with cisplatin, 5-FU and radiation. The changes in the cells were assessed by a cell cytotoxicity assay, Western blotting ( p53 and p21(WAF1/CIP1) proteins), a DNA fragmentation assay, propidium iodide ( PI) staining and DNA flow cytometry. The expression of p53 protein was increased after treatment with cisplatin and 5-FU, but not radiation. The expression of p21(WAF1/CIP1 p)rotein was increased only after treatment with 5-FU, not cisplatin or radiation. With cisplatin and radiation, we observed apoptosis both by DNA fragmentation and PI staining and increased S phase in cisplatin and G2 phase in radiation by DNA flow cytometry. But, with 5-FU, we could not observe apoptosis by DNA fragmentation and PI stain but only an increased G1 phase by DNA flow cytometry. In PNUH-12, radiation induced p53-independent apoptosis and p21(WAF1/CIP1)- independent G2-phase cell cycle arrest. Cisplatin induced p53-dependent apoptosis and p21(WAF1/CIP1)- independent S-phase cell cycle arrest and 5-FU induced p53 and p21(WAF1/ CIP1-)dependent G1-phase cell cycle arrest, not apoptosis. Cisplatin and 5-FU induced p53-dependent pathways, but radiation p53-independent pathway. The cell responses by cisplatin, 5-FU and radiation were all different pathways. Copyright (C) 2005 S. Karger AG, Basel.