A Standardized Evaluation Method for FOXP3+ Tregs and CD8+ T-cells in Breast Carcinoma: Association With Breast Carcinoma Subtypes, Stage and Prognosis

Abstract

Background/aim: The role of FOXP3+ Tregs and CD8+ T-cells in different stages and subtypes of breast carcinoma (BC) is yet to be fully defined, mainly because of methodological variations between studies. The aim of this study was to assess FOXP3+ and CD8+ intratumoral stromal TILs (sTILs) by a standardized method, in order to discern differences between the histological subtypes and BC stage and evaluate the applicability of the method.

Patients and methods: FOXP3+ and CD8+ sTILs were studied immunohistochemically in 207 BCs and counted on digital images, amounting to a standard stromal area of a 10×10 grid on ×40 magnification. The results were correlated with clinicopathological features and outcomes.

Results: Tregs and CD8+ TILs were more abundant in HER2+ BCs (p=0.02, p=0.007, respectively), estrogen receptor (ER)-BCs (p<0.001, for both cell types), and triple-negative BCs (TNBCs) (p=0.01, p=0.006, respectively). Tregs and CD8+ TILs were associated with high grade (p<0.001 and p=0.002, respectively) and high Ki67 index (p<0.001, for both cell types). Lower CD8/FOXP3 ratio was associated with node metastases (p=0.007). Node metastases and advanced stage paralleled with decreased CD8+ sTILs (p=0.023, p=0.019, respectively). In the entire group and in ER- BCs, CD8+ TILs were associated with favorable distant metastasis-free survival (p=0.021, p<0.001, respectively), disease-free survival (p=0.022, p<0.001, respectively) and breast cancer specific survival (BCSS) (p=0.022, p=0.005). In ER-BCs, Tregs were associated with favorable BCSS (p=0.02).

Conclusion: Tregs and CD8+ TILs are higher in early-stage TNBCs and HER2+ BCs and diminish with progression to advanced stages. The findings provide support for immunotherapeutic manipulation of TILs, particularly in early stages of these BC subtypes. The evaluation methodology can be easily implemented for standardization of immunohistochemically-detected TILs.

Keywords: Breast carcinoma; CD8+ T cells; Cytotoxic T lymphocytes (CTLs); FOXP3; TILs; immunosurveillance; regulatory T cells (Tregs).