[A possibility of overcoming local tumor immune tolerance by radiofrequency ablation in combination with intratumoral injection of naïve dendritic cell].

Recently we reported the systemic antitumor efficacy of intratumoral naive dendritic cell injection (IT-DC) in combination with local photodynamic therapy in Clinical Cancer Research 2006. In general, tumor cells secrete several immune suppression cytokines which could induce immune tolerance in a tumor microenvironment. The rationale and advantages of IT DC in combination with conventional antitumor therapy are as follows: (1) dying tumor cells release some tumor antigens, (2) sufficient number of DC recruiting occurs at tumor site, (3) there is naive DC capturing some tumor antigens in vivo, (4) DC activation by inflammatory cytokines are released from dying tumor cells, and (5) DC migration happens in regional lymph nodes and induces adoptive tumor immunity. Conventional antitumor therapy before IT DC could destroy the immune tolerance at a tumor site and induce durable DC vaccination. In this report, we demonstrated the mechanism of (4) and (5) by radiofrequency ablation plus IT DC using mouse tumor model.