title: Homeostatic proliferation plus regulatory T-cell depletion promotes potent rejection of B16 melanoma.
abstract: OBJECTIVE
  To investigate the antitumor efficacy of T-cell anergy reversal through homeostatic proliferation and regulatory T-cell (Treg) depletion in a clinically relevant murine adoptive immunotherapy model.
  
  
  METHODS
  B16 melanoma cells were engineered to express the model SIYRYYGL (SIY) antigen to enable immune monitoring. Tumor-specific T cells expanded in tumor-challenged wild-type hosts but became hyporesponsive. To examine whether lymphopenia-induced homeostatic proliferation could reverse tumor-induced T-cell anergy, total splenic T cells were transferred into lymphopenic RAG2-/- mice or control P14/RAG2-/- mice. Tumor growth was measured, and SIY-specific immune responses were monitored using ELISPOT and SIY/K(b) tetramers. To determine whether Treg depletion could synergize with homeostatic proliferation, RAG2-/- mice received total or CD25-depleted T cells, followed or preceded by B16.SIY challenge. This approach was further investigated in wild-type mice lymphodepleted with sublethal total body irradiation.
  
  
  RESULTS
  Adoptive transfer of total splenic T cells into RAG2-/- mice moderately affected the growth rate of B16.SIY. As Treg expansion occurred in tumor-bearing mice, CD25+ T cells were depleted from total T cells before adoptive transfer. Interestingly, transfer of CD25-depleted T cells into RAG2-/- mice resulted in potent rejection of B16 melanoma in both prophylactic and short-term preimplanted tumor settings and was associated with maintained T-cell effector function. Using a clinically applicable approach, wild-type mice were lymphodepleted using sublethal total body irradiation, which similarly supported tumor rejection upon transfer of CD25-depleted T cells.
  
  
  CONCLUSIONS
  Our results indicate that combined CD25 depletion and homeostatic proliferation support a potent antitumor immune response--an approach with potential for clinical translation.
authors.affiliation: Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Kline
authors.forename: Ian E
authors.initials: IE
authors.lastname: Brown
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Zha
authors.forename: Christian
authors.initials: C
authors.lastname: Blank
authors.forename: John
authors.initials: J
authors.lastname: Strickler
authors.forename: Harald
authors.initials: H
authors.lastname: Wouters
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Gajewski
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D017635:Clonal Anergy; D005434:Flow Cytometry; D006706:Homeostasis / Q000276:immunology*; D016219:Immunotherapy, Adoptive / Q000379:methods*; D008212:Lymphocyte Depletion; D008546:Melanoma, Experimental / Q000276:immunology / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*