It is unknown whether IL-4 induces apoptosis in oral cavity cancer (OCC) cells and, if so, what the mediator of this apoptosis is. Therefore, this study investigated whether apoptosis of OCC cells is induced by IL-4 and whether 15-lipoxygenase-1 (15-LO-1), induced by IL-4, is the mediator of this apoptosis. SCC 1483 oral cavity cancer cells were used in these experiments, and flow cytometry and PARP cleavage were used to examine apoptosis. At an IL-4 dosage that inhibited 50% of cell proliferation, apoptosis was observed, and this apoptosis was inhibited by 2.2 microM caffeic acid (CA). 15-LO-1 mRNA expression was observed beginning at 8 h after treatment with IL-4, and apoptosis increased after 24 h treatment with IL-4. In this apoptosis, the caspase cascade was not involved. In summary, IL-4 induced apoptosis in SCC 1483 OCC cells, and 15-LO-1, induced by IL-4, may mediate this apoptotic pathway.