TOX-expressing terminally exhausted tumor-infiltrating CD8+ T cells are reinvigorated by co-blockade of PD-1 and TIGIT in bladder cancer

Abstract

Exhausted T cells in the tumor microenvironment are major targets of immunotherapies. However, the exhaustion status of CD8⁺ tumor-infiltrating lymphocytes (TILs) in bladder cancer has not been comprehensively evaluated. Herein, we examined distinct exhaustion status of CD8⁺ TILs based on the level of programmed cell death-1 (PD-1) and thymocyte selection-associated high mobility group box protein (TOX) expression in urothelial bladder cancer. We also evaluated the reinvigoration of exhausted CD8⁺ TILs upon ex vivo treatment with inhibitory checkpoint blockers. TOX-expressing PD-1^highCD8⁺ TILs had the highest expression of immune checkpoint receptors (ICRs), the most terminally exhausted features, and the highest tumor antigen reactivity among PD-1⁺CD8⁺ TILs. Bladder cancer patients with a high percentage of PD-1^highTOX⁺CD8⁺ TILs had more progressed T-cell exhaustion features and higher programmed death-ligand 1 expression in tumor tissues. TIGIT was the most frequent co-expressed ICR on PD-1⁺CD8⁺ TILs, and TIGIT blockade enhanced the PD-1 blockade-mediated cytokine production by CD8⁺ TILs from bladder cancer patients. Our findings provide an improved understanding of the heterogeneous exhaustion status of CD8⁺ TILs and additional immunotherapy strategies to improve outcomes of bladder cancer patients.

Keywords: Bladder cancer; CD8(+) T cell; PD-1; TIGIT; TOX.