Tissue resident memory T cells are found in the primary and metastatic tumors of breast cancer patients (TUM2P.922)

Abstract

Abstract Tumor tissues are composed of significant numbers of Tumor Infiltrating Lymphocytes (TILs), which may include CD8+ T cells, CD4+ T cells, and B cells. Of the T cell population, it is known that these cells are often functionally suppressed and defective in their ability to kill and proliferate. However, little is known about how T cells traffic into tumor sites. Furthermore, it is unclear how the various T cell memory subtypes play a role in attempting to eradicate tumor cells. Such knowledge is critical for the development of successful cancer immunotherapies. Here we assayed peripheral blood mononuclear cells (PBMCs), tumor tissue, and sentinel lymph nodes (SLNs) of breast cancer patients to phenotype memory T cells. We found higher proportions of EM cells among CD8 TILs as compared to SLN CD8 T cells. Conversely, the CD4 compartment in both TILs and SLNs was dominated by CM CD4 T cells. Further analysis showed that breast cancer patient CD8+ TILs in primary tumors were made up of a significant population of Tissue Resident Memory cells (TRMs) as identified by CD103 expression and high CD69 expression. We also showed that the CD8+ TILs found in a metastatic brain lesion of a breast cancer patient also contained TRMs. Finally we showed that healthy breast tissue from a patient with no clinical signs of breast cancer also contained CD8+ TRMs.