A novel dendritic cell-based cancer vaccine produces promising results in a syngenic CC-36 murine colon adenocarcinoma model.

Background: This study was conducted to test the efficacy of a new cancer vaccine, composed of dendritic cells (DCs) pulsed with an interleukin-2 gene-encoded vaccinia virus tumor oncolysate (DC-IL-2VCO) in a CC-36 murine colon adenocarcinoma model.

Materials And Methods: CC-36 tumor cells were injected subcutaneously into the left flank of four- to six-week old male BALB/c mice. The mice were divided into three groups, each of which received one of the following treatments: (1) DCs pulsed with the IL-2 gene-encoded vaccinia oncolysate (DC-IL-2VCO), (2) DCs pulsed with the tumor oncolysate alone (DC-CO), or (3) no treatment (control). Tumor incidence was measured, and survival rates were compared using a paired Student's t-test. Cytolytic T cell activity was measured in peripheral blood lymphocytes (PBL) and splenic lymphocytes using a (51)Cr-release assay. Lastly, mice were depleted of either CD4+ or CD8+ lymphocytes prior to receiving the vaccine to test the mechanism of tumor immunity in these mice.

Results: Mice treated with DC-IL-2VCO demonstrated decreased tumor burden, increased survival, and greater cytolytic activity compared with control mice and mice receiving DC-CO. In addition, mice depleted of CD8+ T cells prior to immunization with IL-2VV + DC-IL-2VCO had a significant increase in the incidence of tumor, similar to the untreated control mice.

Conclusions: DCs pulsed with an IL-2 gene-encoded vaccinia virus tumor oncolysate (DC-IL-2VCO) produced safe and effective immune responses in a murine CC-36 colon adenocarcinoma model. This vaccine (DC-MelVac; Patent no. 11221/5) has the potential to treat humans with cancer, and has received FDA approval for use in Phase I clinical trials.