Local TSH/TSHR signaling promotes CD8+ T cell exhaustion and immune evasion in colorectal carcinoma

Cancer Commun (Lond). 2024 Nov;44(11):1287-1310. doi: 10.1002/cac2.12605. Epub 2024 Sep 16.

Abstract

Background: Dysfunction of CD8+ T cells in the tumor microenvironment (TME) contributes to tumor immune escape and immunotherapy tolerance. The effects of hormones such as leptin, steroid hormones, and glucocorticoids on T cell function have been reported previously. However, the mechanism underlying thyroid-stimulating hormone (TSH)/thyroid-stimulating hormone receptor (TSHR) signaling in CD8+ T cell exhaustion and tumor immune evasion remain poorly understood. This study was aimed at investigating the effects of TSH/TSHR signaling on the function of CD8+ T cells and immune evasion in colorectal cancer (CRC).

Methods: TSHR expression levels in CD8+ T cells were assessed with immunofluorescence and flow cytometry. Functional investigations involved manipulation of TSHR expression in cellular and mouse models to study its role in CD8+ T cells. Mechanistic insights were mainly gained through RNA-sequencing, Western blotting, chromatin immunoprecipitation and luciferase activity assay. Immunofluorescence, flow cytometry and Western blotting were used to investigate the source of TSH and TSHR in CRC tissues.

Results: TSHR was highly expressed in cancer cells and CD8+ T cells in CRC tissues. TSH/TSHR signaling was identified as the intrinsic pathway promoting CD8+ T cell exhaustion. Conditional deletion of TSHR in CD8+ tumor-infiltrating lymphocytes (TILs) improved effector differentiation and suppressed the expression of immune checkpoint receptors such as programmed cell death 1 (PD-1) and hepatitis A virus cellular receptor 2 (HAVCR2 or TIM3) through the protein kinase A (PKA)/cAMP-response element binding protein (CREB) signaling pathway. CRC cells secreted TSHR via exosomes to increase the TSHR level in CD8+ T cells, resulting in immunosuppression in the TME. Myeloid-derived suppressor cells (MDSCs) was the main source of TSH within the TME. Low expression of TSHR in CRC was a predictor of immunotherapy response.

Conclusions: The present findings highlighted the role of endogenous TSH/TSHR signaling in CD8+ T cell exhaustion and immune evasion in CRC. TSHR may be suitable as a predictive and therapeutic biomarker in CRC immunotherapy.

Keywords: CD8+ T cell exhaustion; Colorectal carcinoma; Immune evasion; Thyroid stimulating hormone; Thyroid stimulating hormone receptor.

MeSH terms

  • Animals
  • CD8-Positive T-Lymphocytes* / immunology
  • CD8-Positive T-Lymphocytes* / metabolism
  • Cell Line, Tumor
  • Colorectal Neoplasms* / genetics
  • Colorectal Neoplasms* / immunology
  • Colorectal Neoplasms* / metabolism
  • Humans
  • Mice
  • Receptors, Thyrotropin* / genetics
  • Receptors, Thyrotropin* / immunology
  • Receptors, Thyrotropin* / metabolism
  • Signal Transduction*
  • T-Cell Exhaustion
  • Thyrotropin* / metabolism
  • Tumor Escape
  • Tumor Microenvironment* / immunology

Substances

  • Receptors, Thyrotropin
  • Thyrotropin