Tcf-1 protects anti-tumor TCR-engineered CD8 T-cells from GzmB mediated self-destruction.

Background: T-cell longevity is undermined by antigen-driven differentiation programs that render cells prone to attrition through several mechanisms. CD8 T cells that express the Tcf-1 transcription factor have undergone limited differentiation and exhibit stem-cell-like replenishment functions that facilitate persistence. We engineered human CD8 T cells to constitutively express Tcf-1 and a TCR specific for the NY-ESO-1 cancer-associated antigen. Co-engineered cells were assessed for their potential for adoptive cellular immunotherapy.

Methods: Tcf-1 mRNA encoding TCF-1B and TCF-1E isoforms, along with GzmB expression were assessed in CD62L CD57 , CD62L CD57 , and CD62L CD57 CD8 T cells derived from normal donor lymphocytes. The impact of stable Tcf-1B expression on CD8 T-cell phenotype, anti-tumor activity, and cell-cycle activity was assessed in vitro and in an in vivo tumor xenograft model.

Results: TCF-1B and TCF-1E were dynamically regulated during self-renewal, with progeny of recently activated naïve T cells more enriched for TCF-1B mRNA. Constitutive TCF-1B expression improved the survival of TCR-engineered CD8 T cells upon engagement with tumor cells. Tcf-1B prohibited the acquisition of a GzmB  state, and protected T cells from apoptosis associated with elicitation of effector function, and promoted stem cell-like characteristics.

Conclusions: Tcf-1 protects TCR-engineered CD8 T cells from activation induced cell death by restricting GzmB expression. Our study presents constitutive Tcf-1B expression as a potential means to impart therapeutic T cells with attributes of persistence for durable anti-tumor activity.