Soluble CTLA-4 attenuates T cell activation and modulates anti-tumor immunity

Mol Ther. 2024 Feb 7;32(2):457-468. doi: 10.1016/j.ymthe.2023.11.028. Epub 2023 Dec 5.

Abstract

CTLA-4 is a crucial immune checkpoint receptor involved in the maintenance of immune homeostasis, tolerance, and tumor control. Antibodies targeting CTLA-4 have been promising treatments for numerous cancers, but the mechanistic basis of their anti-tumoral immune-boosting effects is poorly understood. Although the ctla4 gene also encodes an alternatively spliced soluble variant (sCTLA-4), preclinical/clinical evaluation of anti-CTLA-4-based immunotherapies have not considered the contribution of this isoform. Here, we explore the functional properties of sCTLA-4 and evaluate the efficacy of isoform-specific anti-sCTLA-4 antibody targeting in a murine cancer model. We show that expression of sCTLA-4 by tumor cells suppresses CD8+ T cells in vitro and accelerates growth and experimental metastasis of murine tumors in vivo. These effects were accompanied by modification of the immune infiltrate, notably restraining CD8+ T cells in a non-cytotoxic state. sCTLA-4 blockade with isoform-specific antibody reversed this restraint, enhancing intratumoral CD8+ T cell activation and cytolytic potential, correlating with therapeutic efficacy and tumor control. This previously unappreciated role of sCTLA-4 suggests that the biology and function of multi-gene products of immune checkpoint receptors need to be fully elucidated for improved mechanistic understanding of cancer immunotherapies.

Keywords: cancer; immune checkpoint; immune regulation; immunomodulation; immunotherapy; soluble CTLA-4.

MeSH terms

  • Animals
  • Antibodies
  • CD8-Positive T-Lymphocytes* / metabolism
  • CTLA-4 Antigen / genetics
  • Mice
  • Neoplasms* / genetics
  • Neoplasms* / therapy
  • Protein Isoforms / genetics

Substances

  • Antibodies
  • CTLA-4 Antigen
  • Protein Isoforms
  • Ctla4 protein, mouse