Prognostic value of tumor-infiltrating Foxp3+ T-cell subpopulations in metastatic melanoma.

Regulatory T cells have already been associated with poor prognosis in various types of cancer. It was previously reported, in ovarian carcinoma, that quantification of Foxp3 identified a subgroup of patients characterized by a significantly worse prognosis in terms of overall survival (OS) and progression-free survival (PFS), suggesting that high expression levels of Foxp3 might represent a surrogate marker for an immunosuppressive microenvironment contributing to tumor immune escape. The main objective of the present study was to precise the prognostic value of Foxp3 regarding PFS and OS in stage III (AJCC) melanoma patients. Total RNA was isolated from 102 metastatic melanoma lymph nodes and from eight tumor-free lymph nodes. Real-time PCR for Foxp3 was performed and correlated with patients' outcome. Quantification of Foxp3 identified a patient subgroup (>90th percentile), which is characterized by a significantly worse prognosis in terms of PFS (P = 0.000271) but not in terms of OS (P = 0.11). In conclusion, quantification of Foxp3 expression using qPCR appears as an independent prognostic factor for PFS in stage III melanoma patients (AJCC). High Foxp3 expression might thus enable the identification of patients most at risk of relapse.