title: In vivo inhibition of human CD19-targeted effector T cells by natural T regulatory cells in a xenotransplant murine model of B cell malignancy.
abstract: Human T cells genetically modified to express chimeric antigen receptors (CAR) specific to the B cell tumor antigen CD19 can successfully eradicate systemic human CD19(+) tumors in immunocompromised SCID (severe combined immunodeficient)-Beige mice. However, in the clinical setting, CD4(+) CD25(hi) T regulatory cells (Treg) present within the tumor microenvironment may be potent suppressors of tumor-targeted effector T cells. In order to assess the impact of Tregs on CAR-modified T cells in the SCID-Beige xenotransplant model, we isolated, genetically targeted and expanded natural T regulatory cells (nTreg). In vitro nTregs modified to express CD19-targeted CARs efficiently inhibited the proliferation of activated human T cells, as well as the capacity of CD19-targeted 19-28z(+) effector T cells to lyse CD19(+) Raji tumor cells. Intravenous infusion of CD19-targeted nTregs into SCID-Beige mice with systemic Raji tumors traffic to sites of tumor and recapitulate a clinically relevant hostile tumor microenvironment. Antitumor efficacy of subsequently infused 19-28z(+) effector T cells was fully abrogated as assessed by long-term survival of treated mice. Optimal suppression by genetically targeted nTregs was dependent on nTreg to effector T-cell ratios and in vivo nTreg activation. Prior infusion of cyclophosphamide in the setting of this nTreg-mediated hostile microenvironment was able to restore the antitumor activity of subsequently infused 19-28z(+) effector T cells through the eradication of tumor-targeted nTregs. These findings have significant implications for the design of future clinical trials utilizing CAR-based adoptive T-cell therapies of cancer.
authors.affiliation: Center for Cell Engineering, Memorial Sloan-Kettering Cancer Center, New York, New York, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Lee
authors.forename: Erik
authors.initials: E
authors.lastname: Hayman
authors.forename: Hollie J
authors.initials: HJ
authors.lastname: Pegram
authors.forename: Elmer
authors.initials: E
authors.lastname: Santos
authors.forename: Glenn
authors.initials: G
authors.lastname: Heller
authors.forename: Michel
authors.initials: M
authors.lastname: Sadelain
authors.forename: Renier
authors.initials: R
authors.lastname: Brentjens
mesh_terms: D000818:Animals; D018941:Antigens, CD19 / Q000276:immunology*; D002051:Burkitt Lymphoma / Q000188:drug therapy / Q000276:immunology / Q000628:therapy*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D003520:Cyclophosphamide / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic; D006801:Humans; D016219:Immunotherapy, Adoptive / Q000379:methods*; D008213:Lymphocyte Activation; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology; D051379:Mice; D016513:Mice, SCID; D041681:NIH 3T3 Cells; D011946:Receptors, Antigen / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D012190:Retroviridae / Q000235:genetics; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014161:Transduction, Genetic; D023041:Xenograft Model Antitumor Assays
chemical_list: D018941:Antigens, CD19; D011946:Receptors, Antigen; D003520:Cyclophosphamide