Pretreatment with 5-FU enhances cisplatin cytotoxicity in head and neck squamous cell carcinoma cells.
OBJECTIVE
In the treatment of head and neck malignancy, cisplatin and 5-FU have been used the most as chemotherapeutic agents. The difference in efficacies of these is unclear and controversial. To investigate more effective schedule, we analyzed the cytotoxicity in different treatment sequence with two agents in vitro and the mechanism for different effectiveness.


METHODS
UM-SCC-23 and UM-SCC-81B, head and neck squamous cell carcinoma cell lines, were analyzed for cellular killing in alternative sequence treatment with cisplatin and 5-FU. The treatment schedule was designed based on the clinical regimen. To determine the mechanism for the difference of cytotoxicity with each schedule, cell cycle distributions of both cells after 5-FU treatment with various durations were analyzed by flow-cytometry and immunostaining with anti-PCNA and anti-BrdU.


RESULTS
5-FU pretreatment followed by cisplatin treatment showed higher cell killing in both types of cells than the reverse treatment schedule. In the cell cycle analysis and immunostaining after the treatment of 5-FU, the rate of PCNA-positive cells was increased from 24 to 144 h in both cells. The rate of BrdU-positive cells of UM-SCC-81B in flow-cytometry was also increased, while that of UM-SCC-23 was gradually decreased. These data suggested that the cells treated with 5-FU for more than 144 h were still in the S-phase with or without DNA synthesis.


CONCLUSIONS
In head and neck carcinoma cells, we showed 5-FU pretreatment enhanced cisplatin cytotoxicity. The result of cell cycle analysis and immunostaining showed S-phase arrest by treatment of prolonged 5-FU treatment. The very long arrest in S-phase might be a mechanism to enhance cisplatin cytotoxicity by 5-FU pretreatment. We thus suggest pretreatment with 5-FU to enhance the effectiveness of cisplatin-based chemotherapy.
Ijichi
Kei
K
Central Laboratory and Radiation Biology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya, Japan. ijichi@aichi-cc.jp
Adachi
Makoto
M
Hasegawa
Yasuhisa
Y
Ogawa
Tetsuya
T
Nakamura
Hideaki
H
Kudoh
Ayumi
A
Yasui
Yoshihiro
Y
Murakami
Shingo
S
Ishizaki
Kanji
K
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D003114:Colony-Forming Units Assay; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D018307:Neoplasms, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis / Q000378:metabolism
D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D018809:Proliferating Cell Nuclear Antigen; D001973:Bromodeoxyuridine; D002945:Cisplatin; D005472:Fluorouracil