Induction of apoptosis in maxillary sinus cancer cells by 5-fluorouracil, vitamin A and radiation (FAR) therapy

The triple combination of 5-fluorouracil (5FU), vitamin A and radiation (FA R therapy) has been used since 1972 to treat malignant tumors of the head a nd neck at Kyushu University. Using nick end labeling of tumor specimens, c ells of human maxillary sinus carcinomas were observed previously to underg o apoptosis in response to FAR therapy. The present study evaluated the in vitro effects of FAR therapy on a human maxillary sinus cancer (IMC-4) cell line. We further compared the effects of FAR therapy on this cell line wit h those effects seen on tissue samples taken from patients with maxillary s inus cancers. DNA electrophoresis and electron microscopic examination of t he IMC-4 cells after treatment with FAR therapy revealed typical apoptotic features. The effects of 50-100 mu g/ml 5-FU, 10(-4) M all-trans-retinoic a cid and radiation to 6 Gy on IMC-4 cells were evaluated by trypan blue dye exclusion and a cell colony formation assay: 5-FU and radiation caused dire ct cell death, while vitamin A mainly inhibited cell growth. The combinatio n of these treatment as FAR therapy synergistically enhanced cell death and inhibited cell growth. Flow cytometry demonstrated that FAR-treated cells were arrested in the G1 phase of the cell cycle before undergoing apoptosis . To further investigate possible biological parameters influencing a tumor 's apoptotic sensitivity, we also examined the expression of p53 in human m axillary sinus cancer cells and analyzed the relationship between p53 expre ssion and apoptosis. However, no relationship was found between these two m arkers at the time point studied.