Immune checkpoint status and exhaustion-related phenotypes of CD8+ T cells from the tumor-draining regional lymph nodes in breast cancer

Abstract

Background: Functional status of T cells determines the responsiveness of cancer patients to immunotherapeutic interventions. Even though T cell-mediated immunity is inaugurated in the tumor-adjacent lymph nodes, peripheral blood has been routinely sampled for testing the immunological assays. The purpose of this study is to determine the immune checkpoint molecule expression and the exhaustion-related phenotype of cytotoxic T cells in the regional lymph nodes from breast cancer patients.

Patients and methods: Multicolor immunophenotyping was used to determine the expression of PD-1, TIM-3, LAG3, CTLA-4, CCR7, CD45RO, CD127, CD25, CXCR5, and ICOS molecules on CD3⁺ CD4^- CD56^- CD8⁺ cytotoxic T cells freshly obtained from the lymph nodes and the peripheral blood samples of the breast cancer patients. The results were assessed together with the clinical data.

Results: A population of cytotoxic T cells was noted with high PD-1 and CXCR5 expression in the lymph nodes of the breast cancer patients. Co-expression of PD-1, CXCR5, TIM-3, and ICOS indicated a follicular helper T cell (Tfh)-like, exhaustion-related immunophenotype in these cytotoxic T cells. Only a minor population with CTLA-4 and LAG3 expression was noted. The PD-1⁺ CXCR5⁺ cytotoxic T cells largely displayed CD45RO⁺ CCR7⁺ central memory markers. The amount of CXCR5-expressing PD-1^- cytotoxic T cells was elevated in the lymph nodes of the patients.

Conclusion: The regional lymph nodes of breast cancer patients harbor Tfh-like exhausted cytotoxic T lymphocytes with high PD-1 and TIM-3 checkpoint molecule expression. The immunological conditions in the regional lymph nodes should be implicated for immune checkpoint immunotherapy (ICI) of cancer.

Keywords: breast cancer; cancer biology; microenvironment; surgical oncology.