title: Cyclophosphamide inhibits the generation and function of CD8(+) regulatory T cells.
abstract: CD8(+) regulatory T cells (Treg) and CD4(+)CD25(+) Treg infiltrate human cancers, thus favoring tumor immune escape. Therefore, in the setting of antitumor therapeutic protocols, it is important to associate antitumor treatment with agents that are able to inhibit Treg function. Cyclophosphamide (CY) has been demonstrated to be effective in counteracting CD4(+)CD25(+) Treg activity. Hence, we tested its inhibitory efficacy on human CD8(+) Treg. Because CY is a prodrug, 4-hydroperoxycyclophosphamide (4-HC), a derivative of CY that in aqueous solution is converted to 4-hydroxycyclophosphamide, an active metabolite of CY, was used. 4-HC significantly inhibited CD8(+) Treg generation and function but only at the higher tested concentration (0.5 μg/mL), that is, in the therapeutic range of the drug. The lower 4-HC concentration tested (0.1 μg/mL) was almost ineffective. 4-HC inhibitory effects were related to apoptosis/necrosis induction. When CD8(+)CD28(+) non-Treg were analyzed for comparative purposes, significantly lower cytotoxic rates among these cells were observed than among CD8(+) Treg, which were differentiated because they did not express the CD28 molecule. These data demonstrate that CD8(+) Treg are inhibited through cytotoxic phenomena by CY, thus supporting the use of this drug at adequate concentrations and schedules of administration as a Treg inhibitor in combinatorial chemo- or immunotherapeutic anticancer protocols.
authors.affiliation: Centre of Excellence for Biomedical Research, University of Genoa, Genoa 16132, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Traverso
authors.forename: Daniela
authors.initials: D
authors.lastname: Fenoglio
authors.forename: Simone
authors.initials: S
authors.lastname: Negrini
authors.forename: Alessia
authors.initials: A
authors.lastname: Parodi
authors.forename: Florinda
authors.initials: F
authors.lastname: Battaglia
authors.forename: Francesca
authors.initials: F
authors.lastname: Kalli
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Conteduca
authors.forename: Samuele
authors.initials: S
authors.lastname: Tardito
authors.forename: Paolo
authors.initials: P
authors.lastname: Traverso
authors.forename: Francesco
authors.initials: F
authors.lastname: Indiveri
authors.forename: Gilberto
authors.initials: G
authors.lastname: Filaci
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D003520:Cyclophosphamide / Q000031:analogs & derivatives / Q000494:pharmacology*; D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects; D016219:Immunotherapy, Adoptive; D009336:Necrosis; D009369:Neoplasms / Q000276:immunology / Q000628:therapy*; D016176:T-Lymphocyte Subsets / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D019139:Tumor Escape / Q000187:drug effects
chemical_list: D018106:CD28 Antigens; D016827:CD8 Antigens; D003520:Cyclophosphamide