Promoter’s Choice Drive CAR-T Efficiency

The development and the functionality of Chimeric Antigen Receptor (CAR) therapy is highly linked to the stability and expression level of the receptor, for which the choice of the promoter is key. Although EF1α is a reference promoter to induce strong antigen binding and long-term CAR expression, we investigated the impact of this one and other constitutive promoters (MSCV, PGK, β2m and CMV) on a CAR123 construct in the Blastic Plasmocytoid Dendritic Cell Neoplasm (BPDCN). Our results indicate that lentiviral vector titer is affected by transgene nature and promoter activity. Interestingly, by moderating the expression level of CAR123 at the cell surface, its recognition capacity and selectivity were improved. We observed that in early stages after transduction, CAR123 expression level did not affect lymphocyte's phenotype and its cytotoxic capacity against BPDCN cell line. However, following long-term culture and decrease of cell-surface CAR expression, a hallmark of transition from activation to memory state of T-cells was observed, and only T-cells transduced with CAR-EF1α or -β2m promoters were still functional. We identified β2m as a promising promoter. Though it shows lower antigen-binding CAR-T cell and antigen recognition rates compared to EF1α, β2m promoter still present interesting CAR expression levels, stability, and binding capacity