Prognostic impact of tumor infiltrating FOXP3 positive regulatory T cells in diffuse large B-cell lymphoma at diagnosis

Tumor-infiltrating immune cells perform a crucial function in host immune reactions against diffuse large B-cell lymphoma (DLBCL). In this study, we have identified a subset of tumor-infiltrating FOXP3-positive regulatory T cells (Tregs) in the initial DLBCL biopsy specimens, and have evaluated their prognostic significance. Ninety six patients with DLBCL were evaluated retrospectively. The pattern of FOXP3 protein expression was evaluated using standard immunohistochemistry in paraffin-embedded tissue samples. Sixty seven of all 96 specimens were stained with antibodies for CD-10, bcl-6 and MUM1 via tissue microarray (TMA) to classify the cases into a germinal center B-cell like (GCB) group and a non-GCB group. The median overall survival (OS) was 28 months. As compared with the others, the patients with higher percentages of FOXP3-positive Tregs on initial tumor biopsy evidenced a significantly longer OS (p = 0.003). Patients classified into the GCB group evidenced a significantly longer OS as compared with the non-GCB group (p = 0.008). When the prognostic factors were evaluated via a multivariate model, the international prognostic index and the percentage of infiltrating FOXP3-positive Tregs in the initial biopsy were identified as independent predictors of OS. In conclusion, the presence of an increased percentage of FOXP3-positive Tregs in DLBCL is predictive of better prognoses.