HLA-A*0201+ Plasmacytoid Dendritic Cells Provide a Cell-Based Immunotherapy for Melanoma Patients

Several sources of evidence suggest that tumor-specific T cells have the potential to control melanoma tumors. Current active and adoptive therapeutic approaches to elicit such T cells are either not sufficiently clinically efficient or require fastidious processes that impede their extensive clinical use. As plasmacytoid dendritic cells (pDCs) have a crucial role in triggering antitumor immunity especially in melanoma, we explored their potential as a cell-based approach for melanoma immunotherapy. An irradiated human HLA-A*0201(+) pDC line loaded with peptides derived from the major melanoma tumor antigens, MelA/MART-1, gp100/pmel17, tyrosinase, and MAGE-A3, was used to trigger functional multi-specific T cells ex vivo from peripheral blood mononuclear cells and tumor-infiltrating lymphocytes from stage I-IV HLA-A* 0201(+) melanoma patients. pDCs loaded with melanoma-derived peptides promptly induced high levels of melanoma tumor-specific T cells from both sources. pDC-primed central/effector memory antitumor T cells were highly functional as indicated by the specific IFN gamma secretion and membrane CD107 expression upon stimulation. Cells also exhibited strong cytotoxicity toward semi-allogeneic melanoma cells and patient-derived tumor cells. The simple design and potent efficacy of this promising approach provides a preclinical basis for the development of a pDC-based vaccine and an alternative means to produce tumor-specific T cells for adoptive cellular immunotherapy in melanoma patients.