Induction of protective antitumor activity of tumor lysate-pulsed dendritic cells vaccine in RM-1 prostate cancer mode

Abstract

Objective To investigate the antitumor activity of tumor lysate-pulsed dendritic cells vaccine in RM-1 prostate cancer mice model with the survival time of mice calculated and the tumor size measured in DC vaccine therapy. Methods C57BL/6 mice were immunized on the dorsal flank by s.c. inoculation of Lysate-DC, ova-DC, and non-DC on day −7. On day 0, 2×10 6 cells of RM-1 tumor cells (H-2 b) were injected s.c. in C57BL/6 mice pre-treated by s.c. inoculation of modified DCs, correspondingly. DTH assay was performed with modified DCs. In partial test, for the determination of which immune cells were required for antitumor activity, mice were immunodepleted of CD4, CD8, or natural killer (NK) NK1.1 cells with the corresponding monoclonal antibodies. The survival time of nude mice loaded with tumor cells was calculated and the size of tumor measured. Results In RM-1 mice prostate cancer model, immunized with lysate-DC, compared with ova-DC and non-DC, the pre-infection vaccine resulted in 100% clearance of primary tumors, whereas on day 0 of injection vaccine cleared 40-60% of primary tumors. On day 0, C57BL/6 mice (H-2 b) were immunized with Lysate-DC, compared with ova-DC and non-DC by caudal vein injection, then on day 15, RM-1 cells were inoculated. On day 30, average diameters of tumor in different groups of modified DC were 23.7±5.4 mm, 22.1±4.9 mm, 4.3±2.6 mm, respectively. Lysate-DC, compared with ova-DC and non-DC, can greatly depressed RM-1 tumor cell growth ( P<0.01). The mean survival time of C57BL/6 mice in Lysate-DC, ova-DC and non-DC groups were 15.8±2.6, 16.6±3.2, 39.0±5.6, respectively, and there was a significant difference in the mean survival time in lysate-DC group between ova-DC and non-DC group ( P<0.01). DTH test showed that lysate-DC could prime T lymphocyte and elicit tumor antigen specific immune response, and over 80% mice in groups of lysate-DC showed obvious swelling in their foot pad. This response was strengthened with repeating inoculation, whereas DTH response was not seen in control group. In vivo depletion of NK cells resulted in a 40-60% reduction in growth suppression within the primary tumor, and depletion of CD4 + cells resulted in a 20% reduction in growth suppression. Conclusion The tumor lysate-pulsed dendritic cells vaccine could elicit antitumor activity in RM-1 loaded C57BL/6 mice, and prolong the duration of RM-1 loaded C57BL/6 mice. So DC-based immunotherapy with hormone-refractory prostate carcinoma yielded protective immunity, generated efficient cellular antitumor responses, thereby providing further preclinical support for feasible immunotherapy approaches for prostate cancer.