Depletion of regulatory T cells in tumors with an anti-CD25 immunotoxin induces CD8 T cell-mediated systemic antitumor immunity

Proc Natl Acad Sci U S A. 2019 Mar 5;116(10):4575-4582. doi: 10.1073/pnas.1820388116. Epub 2019 Feb 13.

Abstract

The tumor microenvironment plays a critical role in controlling tumor progression and immune surveillance. We produced an immunotoxin (2E4-PE38) that kills mouse cells expressing CD25 by attaching the Fv portion of monoclonal antibody 2E4 (anti-mouse CD25) to a 38-kDa portion of Pseudomonas exotoxin A. We employed three mouse cancer tumor models (AB1 mesothelioma, 66c14 breast cancer, and CT26M colon cancer). Tumors were implanted at two sites on BALB/c mice. On days 5 and 9, one tumor was directly injected with 2E4-PE38, and the other was not treated; 2E4-PE38 produced complete regressions of 85% of injected AB1 tumors, 100% of 66c14 tumors, and 100% of CT26M tumors. It also produced complete regressions of 77% of uninjected AB1 tumors, 47% of 66c14 tumors, and 92% of CT26M tumors. Mice with complete regressions of 66c14 tumors were immune to rechallenge with 66c14 cells. Mice with complete regressions of AB1 or CT26M tumors developed cross-tumor immunity rejecting both tumor types. Injection of anti-CD25 antibody or a mutant inactive immunotoxin were generally ineffective. Tumors were analyzed 3 days after 2E4-PE38 injection. The number of regulatory T cells (Tregs) was significantly reduced in the injected tumor but not in the spleen. Injected tumors contained an increase in CD8 T cells expressing IFN-γ, the activation markers CD69 and CD25, and macrophages and conventional dendritic cells. Treatment with antibodies to CD8 abolished the antitumor effect. Selective depletion of Tregs in tumors facilitates the development of a CD8 T cell-dependent antitumor effect in three mouse models.

Keywords: cancer therapy; immunotherapy; intratumoral injection; mesothelioma; regulatory T cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • ADP Ribose Transferases / immunology
  • Animals
  • Antibodies, Monoclonal / administration & dosage*
  • Bacterial Toxins / immunology
  • CD8-Positive T-Lymphocytes / immunology*
  • Cell Line, Tumor
  • Dendritic Cells / immunology
  • Exotoxins / immunology
  • Female
  • Humans
  • Immunity / drug effects
  • Immunotherapy*
  • Immunotoxins / immunology*
  • Interferon-gamma / immunology
  • Interleukin-2 Receptor alpha Subunit / immunology*
  • Lymphocyte Depletion
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Neoplasms / immunology*
  • Neoplasms / therapy*
  • Pseudomonas aeruginosa Exotoxin A
  • T-Lymphocytes, Regulatory / cytology
  • T-Lymphocytes, Regulatory / immunology*
  • Tumor Microenvironment / drug effects
  • Tumor Microenvironment / immunology
  • Virulence Factors / immunology
  • Xenograft Model Antitumor Assays

Substances

  • Antibodies, Monoclonal
  • Bacterial Toxins
  • Exotoxins
  • Immunotoxins
  • Interleukin-2 Receptor alpha Subunit
  • Virulence Factors
  • Interferon-gamma
  • ADP Ribose Transferases