IL-21 Enhances Tumor-Specific CTL Induction by Anti-DR5 Antibody Therapy

Tumor cell apoptosis is the basis of many cancer therapies, and tumor-specific T cells are the principal effectors of successful anti-tumor immunotherapies. In this study, we show that induction of tumor cell apoptosis by agonistic mAb against DR5, combined with delayed IL-21 treatment, suppressed tumor growth and pre-established tumor metastases. Synergistic effects of the combination were observed in several tumor models where the target tumor was sensitive to DR5-mediated apoptosis. IL-21 promoted tumor-specific CTL activity and enhanced memory responses to tumor rechallenge. These results indicate that a rational combination of Ab-based therapy that causes tumor cell apoptosis and a cytokine that promotes T cell memory is a useful new strategy for cancer immunotherapy.