Effect of the combination of a local OK-432 injection and hyperthermia on SCC VII tumors in mice.

Hyperthermia is being investigated as a cancer treatment. Many of its basic mechanisms, particularly those related to cell killing, are still poorly understood. We used a transplanted squamous cell carcinoma cell line to investigate the therapeutic effect of hyperthermia. In particular, we examined the effect of OK-432 (biological response modifier) on hyperthermia-induced apoptosis. In the hyperthermia only group the most extensive necrosis occurred on day 3 (70.3%), and the apoptosis index also was highest on that day (69.3). These results suggest that the induction of apoptosis is closely related to the cell death caused by hyperthermia. The percent of necrosis was significantly higher in the groups given hyperthermia and combined OK-432 and hyperthermia treatment than in the OK-432 group (p < 0.05). The apoptosis index was significantly lower in the combined OK-432 and hyperthermia treatment group than in the hyperthermia only group, indicative that the antitumor effect of combined hyperthermia and OK-432 therapy is not ascribable to the induction of apoptosis.