title: Depletion of CD4+CD25+ regulatory T cells enhances interleukin-2-induced antitumor immunity in a mouse model of colon adenocarcinoma.
abstract: Interleukin 2 (IL)-2 induces antitumor immunity and clinical responses in melanoma and renal cell carcinoma. However, IL-2 also increases the number of CD4(+)CD25(+) regulatory T (Treg) cells that suppress antitumor immune responses. The aim of the present study was to elucidate the effect of depletion of Treg cells on IL-2-induced antitumor immunity. IL-2-transfected mouse colon adenocarcinoma (MC38/IL-2) cells were implanted subcutaneously or intrahepatically into male C57BL/6 mice, and tumor growth and the proportion of tumor-infiltrating lymphocytes with Treg-cell depletion in response to treatment with anti-CD25 monoclonal antibody (PC61) were determined. In mice treated with phosphate-buffered saline, 40-60% of MC38/IL-2 tumors were rejected. In contrast, all MC38/IL-2 tumors were rejected in mice treated with PC61. The number of tumor-infiltrating CD8(+) T cells in mice treated with PC61 was approximately twice that in mice treated with PBS. The numbers of tumor-infiltrating CD4(+) and natural killer cells were also increased significantly. To test the antimetastatic effects of IL-2 treatment in combination with Treg-cell depletion, human recombinant IL-2 (rIL-2) and PC61 were administered to mice implanted with MC38/mock cells in the spleen, and hepatic metastasis was investigated. The average liver weight in mice treated with rIL-2 plus PC61 was 1.04 +/- 0.03 g, less than that in mice treated with rIL-2 (2.04 +/- 0.51 g) or PC61 alone (1.81 +/- 0.38 g). We conclude that IL-2-induced antitumor immunity is enhanced by Treg-cell depletion and is due to expansion of the tumor-infiltrating cytotoxic CD8(+) T-cell population.
authors.affiliation: Department of Oncologic Surgery, Gifu University Graduate School of Medicine, 1-1 Yanagido Gifu, 501-1194, Japan. i2111101@edu.gifu-u.ac.jp
authors.forename: Hisashi
authors.initials: H
authors.lastname: Imai
authors.forename: Masanao
authors.initials: M
authors.lastname: Saio
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nonaka
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Suwa
authors.forename: Naoki
authors.initials: N
authors.lastname: Umemura
authors.forename: Guan-Feng
authors.initials: GF
authors.lastname: Ouyang
authors.forename: Jiro
authors.initials: J
authors.lastname: Nakagawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tomita
authors.forename: Shinji
authors.initials: S
authors.lastname: Osada
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Adachi
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takami
mesh_terms: D000230:Adenocarcinoma / Q000276:immunology*; D000818:Animals; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000276:immunology*; D004195:Disease Models, Animal; D007376:Interleukin-2 / Q000494:pharmacology*; D008212:Lymphocyte Depletion; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009374:Neoplasms, Experimental / Q000276:immunology*; D010957:Plasmids; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014162:Transfection
chemical_list: D007376:Interleukin-2