Deciphering Regulatory Mechanisms by which Glucocorticoid Receptor Signaling Shapes Effector Differentiation of CD8+ Tumor-Infiltrating T Cells

Abstract

CD8+ tumor-infiltrating lymphocytes (TIL) are critical for tumor elimination and undergo a series of states change in the tumor microenvironment (TME), from stem-like T cells (TSL), to cytotoxic effector T cells (Teff), and finally to dysfunctional T cells (Tdys). A prior study indicated that endogenous glucocorticoids (GCs) in the TME shape the effector differentiation of tumor-antigen specific CD8+ T cells, initially restraining the TSL to Teff transition, and subsequently, promoting the development of Tdys. Genetic ablation of the glucocorticoid receptor (GR) specifically in CD8+ T cells improved tumor growth control. However, the mechanisms by which the GR governs the differentiation of CD8+ T cells at different stages remained unclear. In this project, we investigatd how GC signaling impacts on CD8+ T cell state transitions using single-cell RNA sequencing (scRNA-seq) of CD8+ TIL from wildtype (WT) and GR conditional knockout (GRcKO) mice. We found that WT and GRcKO CD8+ T cells differentially accumulate along two distinct differentiation trajectories. WT cells show a delayed transition out of the naïve/stem-like state and preferentially differentiated along a trajectory culminating in dysfunctional T cells. In contrast, GRcKO cells preferentially differentiated along the trajectory culminating in CX3CR1+ effectors and CCL3+CCL4+ cells that share features with tissue-resident memory (TRM) cells and cells present in patients that respond to immune checkpoint blockade (ICB) therapy. Additionally, TCR clonal expansion was more pronounced in the GRcKO cells, particularly in the CX3CR1+ effector cluster. Bioinformatic analysis suggests that this expansion is supported by enhanced glycolysis, indicating a role for GC signaling in regulating the metabolic fitness of CD8+ T cells. We identified Thioredoxin-interacting protein (TXNIP) as a key molecule induced by GR signaling, which can induce cell apoptosis and inhibit glucose transporter 1 (GLUT1) function. Indeed, TXNIP knockout increased CD8+ T cell glucose uptake and enhanced their anti-tumor effects. Our findings provide insight into the effects of GC administration on CD8+ T cell responses and may inform strategies to enhance CD8+ T cell-mediated tumor clearance.