Lah S, Kim S, Kang I, et al. Engineering Second-Generation TCR-T Cells by Site-Specific Integration of TRAF-Binding Motifs into the CD247 Locus. Journal for ImmunoTherapy of Cancer. 2023; 11 (4) (doi: 10.1136/jitc-2022-005519).
Researchers, hoping to modify T-cell receptor-engineered T-cell (TCR-T) therapy for the better, designed a transgenic second-generation TCR-T cell that benefits from co-stimulatory signaling. By altering CD3-zeta genes to contain the intracellular domain (ICD) of the 4-1BB receptor, and then selectively inserting those genes into the CD247 locus, researchers achieved simultaneous recruitment of key adaptor molecules for signals 1 and 2 on TCR engagement. The addition of full-length 4-1BB ICD negatively affected the performance of the resulting TCR-T cells in vivo. As a result, the researchers learned that fusion of minimal necrosis factor receptor-associated factor (TRAF)-binding motifs at the C-terminus of CD3ζ (zBBΔBRM) was itself enough to recruit TRAF2 — the primary adaptor molecule in 4-1BB signaling — without disrupting the expression and proximal signaling of the transgenic TCR. The study authors report that TCR-T cells expressing zBBΔBRM increase persistence and expansion in vitro and in vivo. In a murine xenograft model, the approach yielded robust antitumor activity.