Significance of TIM-3 expression by CD4⁺ and CD8⁺ T lymphocytes in tumor-draining lymph nodes from patients with breast cancer

T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), which is expressed by immune and nonimmune cells, has been shown to play immunoregulatory roles in the tumor microenvironment. In this study we assessed the expression of TIM-3 by T cells from tumor draining lymph nodes (TDLNs) of patients with breast cancer and its association with disease progression. Lymphocytes were isolated from 41 TDLNs, and flow cytometry was used to determine the expression of TIM-3 on CD4(+) and CD8(+) T cells, along with the simultaneous expression of CD25, Foxp3 and TIM-3 in CD4(+) T cells. The results showed that the frequency of TIM-3(+)CD8(+) T cells was associated with higher tumor grade, and the geometric mean fluorescence intensity (gMFI) of TIM-3 in CD4(+) and CD8(+) T cells was significantly higher in patients with more than 9 involved lymph nodes than those with fewer involved nodes. The gMFI of TIM3 in CD4(+) T cells also showed a direct correlation with the number of metastatic lymph nodes. Phenotypic characterization of TIM-3(+)CD4(+) T cells showed that the majority of CD4(+)TIM3(+) lymphocytes were Foxp3(-) CD25(-), and the majority of Foxp3(+)CD25(+) regulatory T cells were TIM-3(-). Our findings showed that TIM-3 was expressed by CD4(+), CD8(+) and regulatory T cells in breast TDLNs, and that expression on CD4(+) and CD8(+) T cells was mostly associated with poor prognosticators such as a higher number of involved lymph nodes or higher tumor grade. More studies are required to confirm TIM-3 as a prognostic marker and a target for immunotherapy in breast cancer.