title: Regulatory Rebound in IL-12-Treated Tumors Is Driven by Uncommitted Peripheral Regulatory T Cells.
abstract: IL-12 promotes a rapid reversal of immune suppression in the tumor microenvironment. However, the adjuvant activity of IL-12 is short-lived due to regulatory T cell (Treg) reinfiltration. Quantitative analysis of Treg kinetics in IL-12-treated tumors and tumor-draining lymph nodes revealed a transient loss followed by a rapid 4-fold expansion of tumor Treg between days 3 and 10. Subset-specific analysis demonstrated that the posttreatment rebound was driven by the CD4(+)CD25(+)Foxp3(+) neuropilin-1(low) peripheral Treg (pTreg), resulting in a 3-5-fold increase in the pTreg to CD4(+)CD25(+)Foxp3(+) neuropilin-1(high) thymic Treg ratio by day 10. The expanding pTreg displayed hypermethylation of the CpG islands in Treg-specific demethylated region, CTLA-4 exon 2, and glucocorticoid-induced TNFR exon 5, were phenotypically unstable, and exhibited diminished suppressive function consistent with an uncommitted in vitro-induced Treg-like phenotype. In vitro culture of posttherapy Treg populations under Th1-promoting conditions resulted in higher levels of IFN-γ production by pTreg compared with thymic Treg, confirming their transitional state. Blockade of selected molecular mechanisms that are known to promote Treg expansion identified IDO-positive dendritic cells as the primary mediator of post-IL-12 pTreg expansion. Clinical implications of these findings are discussed.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KY 40202; and.
authors.forename: Qingsheng
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY 14214.
authors.forename: Lauren P
authors.initials: LP
authors.lastname: Virtuoso
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KY 40202; and.
authors.forename: Charles D
authors.initials: CD
authors.lastname: Anderson
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of Louisville, Louisville, KY 40202; and nejat.egilmez@louisville.edu.
authors.forename: Nejat K
authors.initials: NK
authors.lastname: Egilmez
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism; D060908:CTLA-4 Antigen / Q000235:genetics; D049109:Cell Proliferation; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics; D003713:Dendritic Cells / Q000276:immunology*; D051858:Forkhead Transcription Factors / Q000378:metabolism; D053450:Glucocorticoid-Induced TNFR-Related Protein / Q000235:genetics; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D007108:Immune Tolerance / Q000276:immunology; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology*; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009369:Neoplasms / Q000276:immunology*; D039942:Neuropilin-1 / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D015704:CD4 Antigens; D060908:CTLA-4 Antigen; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D053450:Glucocorticoid-Induced TNFR-Related Protein; C508018:Il2ra protein, mouse; D053645:Interleukin-2 Receptor alpha Subunit; C106544:Tnfrsf18 protein, mouse; D039942:Neuropilin-1; D018664:Interleukin-12; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor