Introduction of genetically modified CD3ζ improves proliferation and persistence of antigen-specific CTLs

The clinical efficacy of T-cell therapies based on T cells transduced with genes encoding tumor-specific T-cell receptors (TCR-T) is related to the in vivo persistence of the T cells. To improve persistence without modifying TCR affinity, we instead modified intracellular signaling, using artificial T cell-activating adapter molecules (ATAM), generated by inserting the intracellular domain (ICD) of activating T-cell signaling moieties into CD3z.ATAMs with the ICD of either CD28 or 4-1BB were generated, assembled into the TCR complex as a part of CD3z, and enhanced downstream signaling from the supramolecular activation cluster.ATAMs were retrovirally introduced into human CMV-specific or NY-ESO-1-specific TCR-transduced CD8lymphocytes, and downstream functionality was then examined.ATAM-transduced NY-ESO-1 TCR-T cells were also investigated using the U266-xenograft mouse model.ATAMs were successfully transduced and localized to the cell membrane.ATAM-transduced CMV-specific T cells retained their cytotoxic activity and cytokine production against peptide-pulsed target cells without altering antigen-specificity and showed resistance to activation-induced cell death. Upon both single and repeated stimulation, CD3z/4-1BB-transduced T cells had superior proliferation to the CD3z-transduced T cells in both the CMV-specific and the NY-ESO-1 TCR-T models and significantly improved antitumor activity compared with untransduced T cells both in vitro and in a mouse xenograft model.ATAM-transduced TCR-T cells demonstrated improved proliferation and persistence in vitro and in vivo. This strategy to control the intracellular signaling of TCR-T cells by ATAM transduction in combination with various tumor-specific TCRs may improve the efficacy of TCR-T therapy. Cancer Immunol Res; 6(6); 733-44.