Transferrin epitope-CD19-CAR-T cells effectively kill lymphoma cells in vitro and in vivo

Chimeric antigen receptor (CAR) T cell immunotherapy has demonstrated clinical success in treatment of B-cell hematologic cancers. In this study, we compared human Transferrin epitope tagged CAR-T cells with non-tagged CAR-T cells for cytotoxicity, IFN-gamma secretion and tumor clearance in NSG mice. CD19-TF-CAR-T cells had similar cytotoxicity in vitro to CD19-CAR-T cells against cells expressing CD19 antigen: exogenously CD19⁺ Hela cells and endogenously CD19⁺ Raji cells. In addition, CD22-TF CAR-T cells were similarly cytotoxic against CD22⁺ CHO cells and CD22⁺  Raji cells. Both CD19-TF or CD22-TF-CAR-T cells secreted less IFN-gamma as compared to non-tagged CAR-T cells. In a Raji xenograft NSG mouse model, CD19-TF-CAR-T cells were as effective as CD19-CAR-T cells in reducing tumor growth and extending mouse survival. The results show that CD19-TF-CAR-T cells can be monitored using TF antibody in vitro and ex vivo, and that these cells effectively killed Raji cells in vitro and in vivo with reduced secretion of IFN-gamma. Thus, these TF-tagged CAR-T cells might have improved safety and provide a basis for future clinical studies.