title: Local secretion of IL-12 augments the therapeutic impact of dendritic cell-tumor cell fusion vaccination.
abstract: BACKGROUND
  The development of dendritic cell (DC)-tumor fusion vaccines is a promising approach in cancer immunotherapy. Using fusion vaccines allows a broad spectrum of known and unidentified tumor-associated antigens to be presented in the context of MHC class I and class II molecules, with potent co-stimulation provided by the DCs. Although DC-tumor fusion cells are immunogenic, murine studies have shown that effective immunotherapy requires a third signal, which can be provided by exogenous interleukin 12 (IL-12). Unfortunately, systemic administration of IL-12 induces severe toxicity in cancer patients, potentially precluding clinical use of this cytokine to augment fusion vaccine efficacy. To overcome this limitation, we developed a novel approach in which DC-tumor fusion cells locally secrete IL-12, then evaluated the effectiveness of this approach in a murine B16 melanoma model.
  
  
  METHODS
  Tumor cells were stably transduced to secrete murine IL-12p70. These tumor cells were then electrofused to DC to form DC-tumor heterokaryons. These cells were used to treat established B16 pulmonary metastases. Enumeration of these metastases was performed and compared between experimental groups using Wilcoxon rank sum test. Interferon γ enzyme-linked immunosorbent spot assay was performed on splenocytes from treated mice.
  
  
  RESULTS
  We show that vaccination with DCs fused to syngeneic melanoma cells that stably express murine IL-12p70 significantly reduces counts of established lung metastases in treated animals when compared with DC-tumor alone (P = 0.029). Interferon γ enzyme-linked immunosorbent spot assays suggest that this antitumor response is mediated by CD4(+) T cells, in the absence of a tumor-specific CD8(+) T cell response, and that the concomitant induction of antitumor CD4(+) and CD8(+) T cell responses required exogenous IL-12.
  
  
  CONCLUSIONS
  This study is, to the best of our knowledge, the first report that investigates the impact of local secretion of IL-12 on antitumor immunity induced by a DC-tumor fusion cell vaccine in a melanoma model and may aid the rational design of future clinical trials.
authors.affiliation: Division of Otolaryngology, Duke University Medical Center, Durham, North Carolina.
authors.forename: Chunrui
authors.initials: C
authors.lastname: Tan
authors.forename: Jens
authors.initials: J
authors.lastname: Dannull
authors.forename: Smita K
authors.initials: SK
authors.lastname: Nair
authors.forename: Enyu
authors.initials: E
authors.lastname: Ding
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Tyler
authors.forename: Scott K
authors.initials: SK
authors.lastname: Pruitt
authors.forename: Walter T
authors.initials: WT
authors.lastname: Lee
mesh_terms: D000818:Animals; D019496:Cancer Vaccines / Q000494:pharmacology; D045744:Cell Line, Tumor; D003713:Dendritic Cells / Q000473:pathology / Q000637:transplantation*; D004195:Disease Models, Animal; D005260:Female; D006822:Hybrid Cells / Q000378:metabolism; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D018664:Interleukin-12 / Q000235:genetics / Q000378:metabolism*; D007763:Lac Operon / Q000235:genetics; D008175:Lung Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D008546:Melanoma, Experimental / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D014611:Vaccination / Q000379:methods*
chemical_list: D019496:Cancer Vaccines; D018664:Interleukin-12; D007371:Interferon-gamma
keywords: Animal model; Dendritic cell; ELISPOT; Electrofusion; Fusion hybrids; Immunotherapy; Interleukin 12; Melanoma; T cell; Vaccine