Therapeutic CAR T cells differentiate into diverse memory and exhausted T cell subsets in vivo to provide long-term protection from relapse and metastasis of solid tumors.

Abstract

Abstract Canonical memory T cell differentiation is programmed during the early stages of priming by a multitude of variables such as TCR signal strength, duration of antigenic exposure, and the milieu of cytokines. A combination of such stochastic variables in vivo, drive a heterogeneity in T cell priming that leads to the generation of distinct subsets of T cell effector and memory lineages. Contrarily, CAR T cell priming is largely homogenous and the diversity of the ensuing memory CAR T cells following adoptive immunotherapy remains largely unknown. In this study, we show that following adoptive immunotherapy into solid tumor bearing mice, syngeneic CAR T cells differentiate into distinct memory T cell subsets. In the peripheral tissues and lymphoid organs, CAR T cells subsets of central memory (T CM), effector memory (T EM) and resident memory (T RM) were fully represented. Furthermore, within the tumor microenvironment, distinct lineages of exhausted T cells such as progenitor exhausted (T PEX) and terminally exhausted (T EX) CAR T cells were found. When benchmarked against gold-standard T cells programmed in vivo by viral infections, the subsets of CAR memory and exhausted T cells demonstrated the hallmark qualities of protection from metastasis, and responsiveness to checkpoint blockade, respectively. These findings are among the first to demonstrate that CAR T cells differentiate into a full-spectrum of memory and exhausted T cell subsets in therapeutic applications against solid tumors. Comprehensive understandings of CAR T cell memory and exhaustion programs would be critical in developing therapeutic CAR T cells that provide long-term protection from tumor relapse, tumor metastasis and responsiveness to checkpoint blockade. Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under Award Number F32CA265056. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health