Interleukin-2 administration after modified radical mastectomy in breast cancer therapy increases peripheral regulatory T cells

Background: Breast cancer (BC) deaths are a major concern worldwide, and modified radical mastectomy (MRM) still represents a primary therapeutic strategy. Post-surgery administration of interleukin (IL)-2 for BC therapy has been implemented in China recently. Although its impact on regulatory T cells (Tregs) has been documented in some cancer types, such as melanoma, the IL-2-mediated changes in the Treg composition after MRM in BC treatment remain unknown. Methods: As registered with the Chinese Clinical Trial Registry, 34 newly diagnosed BC patients, aged 20-65 years, were enrolled in this trial. Patients were randomized to the IL-2-treated group (n=15) and the untreated control group (n=19). Peripheral blood mononuclear cells were isolated at time points of preoperation (PreOP) and post-operation Day 1 (POD1), POD3, and POD7. Cells were subjected to flow cytometric assays to identify CD4(+) CD25(+) Foxp3(+) Tregs, as well as real-time quantitative polymerase chain reaction analysis of FOXP3 expression. Results: We found that the surgery caused a significant decrease in the percentage of Tregs on POD1, followed by a significant increase characterized by a peak value on POD7 with a more than 18% increase relative to the Pre-OP levels. We observed that the Treg percentages in the IL-2-treated group were significantly greater than those in the control group on POD3 and POD7, whereas no such statistical difference was observed on POD1. The FOXP3 expression analysis revealed consistent trends as observed by flow cytometry. Conclusions: Post-operative administration of IL-2 amplifies the surgery-induced augmentation of both Tregs and FOXP3 expression in BC therapy.