Cytokine-gene-modified tumor vaccination intensified by a streptococcal preparation OK-432.

Vaccinations with tumor cells engineered to express certain cytokines have been demonstrated to induce potent and specific antitumor immunity. In our previous report, we carried out a comparative study on the ability of cytokine-gene-modified tumor vaccines to induce host immune responses, and found that irradiated tumor cells, genetically modified to secrete granulocyte/macrophage-colony-stimulating factor (GM-CSF tumor vaccine), were the most potent stimulators of systemic antitumor immunity. In this report, using the experimental tumor models in which the GM-CSF tumor vaccine was less effective in immunopotentiation, we found that the combined use of a biological response modifier (BRM) OK-432 remarkably enhanced the antitumor activity induced by the GM-CSF tumor vaccine. These data indicate the possible role of a BRM such as OK-432 to intensify further the specific tumor vaccination therapy.