5-Fluorouracil-induced apoptosis in cultured oral cancer cells

Chemotherapy is commonly used to treat advanced oral squamous cell carcinom a (SCC) and is known to kill cancer cells through apoptosis. Our hypothesis states that 5-fluorouracil (5FU) also kills cultured oral epithelial cells through programmed cell death or apoptosis. Cultured oral cancer cells wer e exposed to an optimum dose of 20 mg:ml of 5FU. Cells were analyzed for ch anges in cell cycle distribution and induction of cell death including apop tosis. Normal control, human papilloma virus-immortalized (PP), ATCC SCC ce ll line (CA1) and two primary oral SCC cell lines (CA3 and -4) were studied . Inhibition of apoptosis by a pan-caspase inhibitor was used. SYTO 11 flow cytometry showed increased apoptosis in all SFU-treated cell cultures comp ared to untreated controls. The results show biological variation in apopto tic response. Chl had the lowest apoptotic rate of the cancer cell lines at 1.5%. Next lowest was CA3, followed by CA4 and PP. In addition, alteration in the G1 and S phase fractions were found. Untreated CAI showed 28% G1, 5 3% S compared to 43% G11 and 40% S of treated. We investigated the pathway of apoptosis using the pan-caspase inhibitor IDN-1529 by methylthiazolyl di phenyl tetrazolium bromide (MTT) colorimetric analysis. Results showed mild inhibition of cell death when cells were incubated with 50 mu M IDN-1529 f or 24 h. This suggests a probable caspase-dependent apoptotic pathway. In c onclusion, our data suggest that 5FU induces oral cancer cell death through apoptosis and that biological variation exists between normal and cancer c ells and between different types of cancer cells themselves. Our data indic ate that cultures of a useful in vitro model for chemosensitivity assays ar e possible. Our results also suggest a caspase-dependent pathway for chemoc ytotoxicity in oral SCC. (C) 2000 Elsevier Science Ltd. All rights reserved .