Accumulation of Regulatory T Cells in Triple Negative Breast Cancer Can Boost Immune Disruption

The present study was conducted to evaluate the number of Tregs in triple negative breast cancer (TNBC), in normal breast parenchyma and in the peripheral blood of these patients and controls, in addition to their correlations with the clinico-pathologic features and the outcomes of TNBC.

Thirty adult treatment-naïve women with non-metastatic TNBC were recruited. In addition, 20 ages matched healthy females participated as a control group. Peripheral blood samples were collected from all participants in tubes containing heparin, fresh tumor tissues were also obtained from all patients undergoing surgery, and 20 normal breast tissue samples were obtained from the same patients' areas adjacent to the safety margins; all these samples were taken for flow cytometric detection of Tregs.

The mean percentages of CD4⁺CD25^+highT cells and Tregs were higher in TNBC peripheral blood than healthy controls and in malignant tissue than normal tissue. Moreover, the frequencies of tumor-infiltrating CD4⁺T cells and Tregs were exceeding those in the peripheral blood of cancer patients. Only tumor-infiltrating Tregs have shown increasing levels with the increase in the tumor size and were significantly higher in patients with local recurrences than those without recurrence. In addition, Tregs showed significant inverse relation with DFS and direct relation with the level of the peripheral Tregs.

The findings of the current study support the possibility that TNBC microenvironment conveys specific characteristics on Tregs distinguishing them from those in normal breast tissue or Tregs in peripheral blood, improving the capabilities of tumor-infiltrating Tregs to enhance tumor growth, local recurrence and reduce the DFS.