New strategy for efficient selection of dendritic cell-tumor hybrids and clonal heterogeneity of resulting hybrids

Abstract

Heterotypic hybrids created between dendritic cells (DC) and tumor cells represent an efficient approach for loading DC with tumor-associated antigens (TAA), and DC-tumor hybrid vaccines have shown promising outcomes in various preclinical and clinical studies. Conventional DC-tumor hybrid preparations, however, are unavoidably contaminated by DCtumor aggregates and DC loaded with tumor cell debris. Here we describe a new strategy for selecting genuine DC-tumor hybrids. A HAT-sensitive/zeocin-resistant DC clone (XS106-7 Zeo) was fused with a GFP-transduced fibrosarcoma clone (S1509a-GFP) by polyethylene glycol and heterotypic hybrid clones were established by limiting dilution in the presence of HAT and zeocin. CD45 (DC origin) and GFP (tumor origin) were both expressed in 91% (51/56 clones) of the resulting clones, indicating high efficiency of our strategy. Marked heterogeneity was observed among the hybrid clones, and only one clone exhibited characteristic features of DC (CD86 and I-A expression, dendritic morphology, T cellstimulatory capacity, and IL-1b, IL-6, and TNFa production), suggesting that only small fractions of DC-tumor hybrids acquire and maintain the properties of parental DC. Finally, vaccination with this hybrid clone protected mice from subsequent growth of S1509a tumor cells, documenting the in vivo activity of DC-tumor hybrids in the complete absence of exogenous TAA.