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* Dana-Farber Cancer Institute, Dana-Farber/Harvard Cancer Center,
Center for Molecular Orthopaedics, Brigham & Womens Hospital, and
Beth Israel Deaconess Medical Center, Boston, MA 02115
Vaccination of patients with dendritic cell (DC)/breast carcinoma fusions stimulated antitumor immune responses in a majority of patients with metastatic disease but only a subset demonstrate evidence of tumor regression. To define the factors that limit vaccine efficacy, we examined the biological characteristics of DC/breast carcinoma fusions as APCs and the nature of the vaccine-mediated T cell response. We demonstrate that fusion of DCs with breast carcinoma cells up-regulates expression of costimulatory and maturation markers and results in high levels of expression of IL-12 consistent with their role as activated APCs. Fusion cells also express the chemokine receptor CCR7, consistent with their ability to migrate to the draining lymph node. However, DC/breast cancer fusions stimulate a mixed T cell response characterized by the expansion of both activated and regulatory T cell populations, the latter of which is characterized by expression of CTLA-4, FOXP3, IL-10, and the suppression of T cell responses. Our results demonstrate that IL-12, IL-18, and TLR 9 agonist CpG oligodeoxynucleotides reduce the level of fusion-mediated regulatory T cell expansion. Our results also demonstrate that sequential stimulation with DC/breast carcinoma fusions and anti-CD3/CD28 results in the marked expansion of activated tumor-specific T cells. These findings suggest that DC/breast carcinoma fusions are effective APCs, but stimulate inhibitory T cells that limit vaccine efficacy. In contrast, exposure to TLR agonists, stimulatory cytokines, and anti-CD3/CD28 enhances vaccine efficacy by limiting the regulatory T cell response and promoting expansion of activated effector cells.
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1 This work was supported by the Department of Defense Grant DAMD17-03-1-0487 and in part by Dana-Farber Cancer Institute/Harvard Cancer Center Ovarian Cancer Specialized Program of Research Excellence Grant P50CA105009-04.
2 Address correspondence and reprint requests to Dr. David Avigan, Hematologic Malignancy/Bone Marrow Transplant Program, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, KS-135, Boston, MA 02115. E-mail address: davigan{at}bidmc.harvard.edu
3 Abbreviations used in this paper: DC, dendritic cell; ODN, oligodeoxynucleotide; PEG, polyethylene glycol; SI, stimulation index; CBA, cytometric bead array; GITR, glucocorticoid-induced TNF receptor.
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