Although the presence of tumor-infiltrating lymphocytes (TILs) indicates an endogenous antitumor response, immune regulatory pathways can subvert the effector phase and enable tumor escape. Negative regulatory pathways include extrinsic suppression mechanisms, but also a T cell–intrinsic dysfunctional state. A more detailed study has been hampered by a lack of cell surface markers defining tumor-specific dysfunctional TILs, and PD-1 alone is not sufficient. Recently, we identified the transcription factor Egr2 as a critical component in controlling the anergic state in vitro. In this study, we show that the Egr2-driven cell surface proteins LAG-3 and 4-1BB can identify dysfunctional tumor antigen–specific CD8+ TIL. Co-expression of 4-1BB and LAG-3 was seen on a majority of CD8+ TILs, but not in lymphoid organs. Functional analysis revealed defective IL-2 and TNF production yet retained expression of IFN-γ and regulatory T cell–recruiting chemokines. Transcriptional and phenotypic characterization revealed coexpression of multiple additional co-stimulatory and co-inhibitory receptors. Administration of anti–LAG-3 plus anti–4-1BB mAbs was therapeutic against tumors in vivo, which correlated with phenotypic normalization. Our results indicate that coexpression of LAG-3 and 4-1BB characterize dysfunctional T cells within tumors, and that targeting these receptors has therapeutic utility.
- Submitted: 4 April 2016
- Revision received 8 September 2016
- Accepted: 15 December 2016
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