The role of FOXP3 of interstitial tissue in the pathogenesis of breast cancer

Background: The study aimed to evaluate the expression level of FOXP3 and the degree of FOXP3 positive lymphocytes in the interstitial tissues of normal breast tissues, primary breast cancer tissues and axillary lymph node metastatic cancer tissues, so as to better clarify FOXP3's role in the process of breast cancer tumorigenesis and progression. Methods: FOXP3 protein expression and FOXP3 positive tumor infiltrating lymphocytes were investigated by immunohistochemistry analysis in normal breast tissues, primary breast cancer tissues and axillary lymph node metastatic cancer tissues achieved from 44 patients. Results: Compared to normal breast tissues, the expression of FOXP3 in interstitial tissues in primary and metastatic cancer tissues was significantly up-regulated. The FOXP3 positive lymphocytes infiltrated interstitial tissues in 30 of 44 (68.2%) specimens of normal breast tissues, 40 of 44 (90.9%) specimens of primary cancer tissues and 42 of 44 (95.5%) specimens of axillary lymph node metastatic cancer tissues. There was linear correlation trend between FOXP3 expression and the process transforming from normal breast epithelium to primary cancer and metastatic cancer, indicating its potential role in the pathogenesis of this disease. And we found that the expression of interstitial FOXP3 in axillary lymph node metastatic cancer site was correlated with the lymph node ratio (LNR), and LNR was higher in the FOXP3 positive expression group than the FOXP3 absent group. Conclusions: Increased FOXP3 expression in cancer interstitial tissues and FOXP3 positive lymphocytes infiltration might have a certain correlation with the development of breast cancer through facilitating immune escape of tumor.