Autologous dendritic cells loaded with apoptotic tumor cells induce T cell-mediated immune responses against breast cancer in vitro

Dendritic cell (DCs) based immunotherapy has received increased interest in the treatment of specific malignancies including breast cancer. In this in vitro study, T cell responses, which are induced by monocyte-derived DCs pulsed with apoptotic breast tumor cells (ApTC), were analyzed in terms of proliferation, specific cytotoxicity, and cytokine release. Nylon wool-enriched T lymphocytes from five patients with breast cancer stimulated with monocyte-derived DCs pulsed with apoptotic tumor cells in vitro and their proliferation response were analyzed by [3H] thymidine uptake and specific cytotoxic activity of tumor antigen-primed T cells after three rounds of weekly stimulation by flow cytometry. Interferon-γ (IFN-γ) and interleukin-4 (IL-4) cytokine release assay was carried out 24 h after the last stimulation. The supernatant from primed T cells was collected and analyzed using commercially available ELISA kits. T cell proliferation assays revealed that DCs pulsed with apoptotic tumor cell could stimulate an autologous T cell proliferation response with stimulation indices of 5-21. The T cell-mediated cytotoxicity assay demonstrated that tumor antigen-primed T cells could kill significantly more autologous tumor cells than normal cells (P < 0.05). These cells had variable amounts of cytotoxic activity against K562 cells. Primed T cells released both IFN-γ and IL-4 in response to re-stimulation by antigen-pulsed DCs, but were dominated by IFN-γ production in two out of five patients and IL-4 production in three out of five patients. In conclusion, our results suggested that DCs pulsed with apoptotic breast tumor cells could elicit effective specific antitumor T cell responses in vitro. Therefore, vaccination with DCs pulsed with apoptotic tumor cells may be considered as a novel strategy for immunotherapy of patients with breast cancer refractory to standard modalities.