Combining a chimeric antigen receptor and a conventional T-cell receptor to generate T cells expressing two additional receptors (TETARs) for a multi-hit immunotherapy of melanoma.

The adoptive transfer of engineered T cells represents an important approach in immunotherapy of melanoma. However, relapse of the tumor can occur due to immune-escape mechanisms developed by the tumor cells, for example antigen loss, downregulation of the major histocompatibility complex presentation machinery and defects in antigen processing. To counteract these mechanisms, we combined a T-cell receptor and a chimeric antigen receptor, specific for different common melanoma antigens, gp100 (PMEL) and MCSP (HMW-MAA), to generate functional CD8+ T cells expressing two additional receptors (TETARs) by electroporation of receptor-encoding mRNA. These TETARs produced cytokines and were lytic upon recognition of each of their cognate antigens, while no reciprocal inhibition of the receptors occurred. When stimulated with target cells, which express both antigens, an enhanced effect was suggested. The confirmation that chimeric antigen receptors and T-cell receptors can be functionally combined opens up new avenues in cancer immunotherapy, and the generation of TETARs helps by-passing major mechanisms by which tumor cells escape immune recognition.