Increase of CD4+CD25+ regulatory T cells in the peripheral blood of patients with metastatic carcinoma:: a Phase I clinical trial using cyclophosphamide and immunotherapy to eliminate CD4+CD25+ T lymphocytes

We determined the number and functional status of CD4(+)CD25(high) regulatory T cells (T-reg) in blood samples from patients with metastatic carcinoma, and evaluated their sensitivity to a single intravenous infusion of cyclophosphamide. T-reg numbers were significantly higher in 49 patients with metastatic cancer (9.2% of CD4(+) T cells) compared to 24 healthy donors (7.1%). These cells expressed the transcription factor forkhead box P3 (FoxP3), glucocorticoid-induced tumour necrosis factor receptor family-related protein (GITR) and intracellular CD152, and demonstrated a suppressive activity in vitro against CD4(+)CD25(-) autologous proliferation. At a single intravenous infusion, cyclophosphamide failed, in association with a non-specific immunotherapy by intratumoral bacille Calmette-Guerin (BCG), to modulate significantly T-reg numbers or function. Metastatic cancer is associated with an expansion of peripheral blood CD4(+)CD25(high)FoxP3(+)GITR(+)CD152(+)T(reg) cells whose immunosuppressive properties do not differ from those of healthy subjects. Moreover, cyclophosphamide administration may not represent an optimal therapy to eliminate T-reg, which further underlines the need to identify specific agents that would selectively deplete these cells.