[Show abstract][Hide abstract] ABSTRACT: It was hypothesized that if dendritic cells (DC) could be efficiently manipulated in vivo, this might enable functional maturation and retention of their potent functions and might represent a more promising approach in DC immunotherapy. The present study focused on the modulation of DC in tumor microenvironment using Fms-like thyrosine kinase 3 ligand (Flt3L) combined with interferon-gamma-inducing factor (IL-18). Tumor-inoculated mice were treated with in vivo electroporation (IVE) of expression plasmids carrying complementary DNA of Flt3L. As a combination therapy, mice in the other group were treated with intra-tumoral injection of adenoviral vector carrying IL-18 gene (Ad.IL-18). Significant antitumor effect was observed in mice treated with Ad.IL-18 alone when compared with that of control (P < 0.01). Complete eradication was observed more frequently (100%versus 33%: P < 0.05) in the mice treated with Flt3L and Ad.IL-18 when compared with the mice treated with Ad.IL-18 alone. In un-injected distant tumor, significant antitumor responses were observed only in the mice treated with combination therapy. Lymphoid cells in lymph nodes of mice treated with combination therapy showed significant cytolytic activity against inoculated tumor cells and YAC-1 cells when compared with the lymphoid cells in other groups. In the tumor microenvironment, combination therapy resulted in the recruitment of mobilized DC into the tumor bed, although Flt3L-IVE alone had an effect in the peri-tumoral area. Tumor-infiltrating DC in mice treated with combination therapy showed higher CD86 expression and more potent allogeneic T-cell stimulatory capacity. These results may suggest that local expression of IL-18 combined with in vivo DC mobilization with Flt3L is clinically applicable as a new strategy of DC immunotherapy.
[Show abstract][Hide abstract] ABSTRACT: Angiogenesis is a critical mechanism for tumor progression. Multiple studies have suggested that tumor growth can be suppressed if tumor angiogenesis can be inhibited using various types of antiangiogenic agents. Recent studies in mouse systems have shown that tumor angiogenesis can also be inhibited if cellular immune response could be induced against vascular endothelial growth factor receptor 2 (VEGFR2), which is one of the key factors in tumor angiogenesis. In this study, we examined the possibility of developing this novel immunotherapy in clinical setting. We first identified the epitope peptides of VEGFR2 and showed that stimulation using these peptides induces CTLs with potent cytotoxicity in the HLA class I-restricted fashion against not only peptide-pulsed target cells but also endothelial cells endogenously expressing VEGFR2. In A2/Kb transgenic mice that express alpha1 and alpha2 domains of human HLA-A*0201, vaccination using these epitope peptides in vivo was associated with significant suppression of the tumor growth and prolongation of the animal survival without fatal adverse effects. In antiangiogenesis assay, tumor-induced angiogenesis was significantly suppressed with the vaccination using these epitope peptides. Furthermore, CTLs specific to the epitope peptides were successfully induced in cancer patients, and the specificities of the CTLs were confirmed using functional and HLA-tetramer analysis. These results in vitro and in vivo strongly suggest that the epitope peptides derived from VEGFR2 could be used as the agents for antiangiogenic immunotherapy against cancer in clinical settings.