Tumoral FOXP3 has potential oncogenic function in conjunction with the p53 tumor suppressor protein and infiltrated Tregs in human breast carcinomas.

FOXP3 is a transcription factor and a well-known hallmark of immune suppressive T regulatory cells. Recent studies indicate that in tumor cells, FOXP3 plays an important role in tumor development in addition to its well-established Treg function in the immune system. We investigated tumoral FOXP3 expression in breast carcinoma, and the relationships between tumoral FOXP3 expression and p53, HER-2/ErbB2, Ki67, infiltrated Tregs, and other clinicopathological variables. Tissue samples from 272 cases of breast carcinoma were used. We assessed tumoral FOXP3, p53, HER-2/ErbB2, Ki67, and infiltrated Tregs using immunohistochemical staining. Positive expression of tumoral FOXP3 was observed in 38.6% (105/272) of breast carcinomas. Positive tumoral FOXP3 expression was significantly related with positive p53 and higher Ki67 expression. Higher histological grade was significantly correlated to increased tumoral FOXP3 expression. Tumoral FOXP3 expression was positively correlated with infiltrated FOXP3-expressing Tregs. From these data, we argue that tumoral FOXP3 has a potential oncogenic function in conjunction with the p53 tumor suppressor protein and infiltrated Tregs in human breast carcinomas.