In a study of MBC patients, 30 days of metronomic low-dose CTX treatment selectively depleted CD4+ CD25+ Foxp3+ Treg [10], suggesting that prolonged treatment with low-dose CTX may not only control immune suppression by Treg, but also support spontaneous anti-tumor T-cell responses and thereby clinical outcome of MBC patients. The gene discussed is CD4; the disease is neoplasm.