Class I Histone Deacetylase Inhibitor Entinostat Suppresses Regulatory T Cells and Enhances Immunotherapies in Renal and Prostate Cancer Models

PLoS One. 2012;7(1):e30815. doi: 10.1371/journal.pone.0030815. Epub 2012 Jan 27.

Abstract

Background: Immunosuppressive factors such as regulatory T cells (Tregs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been reported to have antitumor activity in different malignancies and immunomodulatory effects. Herein, we report the Tregs-targeting and immune-promoting effect of a class I specific HDAC inhibitor, entinostat, in combination with either IL-2 in a murine renal cell carcinoma (RENCA) model or a survivin-based vaccine therapy (SurVaxM) in a castration resistant prostate cancer (CR Myc-CaP) model.

Methods and results: RENCA or CR Myc-CaP tumors were implanted orthotopically or subcutaneously, respectively. Inoculated mice were randomized into four treatment groups: vehicle, entinostat, cytokine or vaccine, and combination. Tregs in the blood were assessed by FACS analysis. Real time quantitative PCR and Western blot analysis of isolated T cell subpopulations from spleen were performed to determine Foxp3 gene and protein expression. The suppressive function of Tregs was tested by T cell proliferation assay. Low dose (5 mg/kg) entinostat reduced Foxp3 levels in Tregs and this was associated with enhanced tumor growth inhibition in combination with either IL-2 or a SurVaxM vaccine. Entinostat down-regulated Foxp3 expression transcriptionally and blocked Tregs suppressive function without affecting T effector cells (Teffs). In vitro low dose entinostat (0.5 µM) induced STAT3 acetylation and a specific inhibitor of STAT3 partially rescued entinostat-induced down-regulation of Foxp3, suggesting that STAT3 signaling is involved in Foxp3 down-regulation by entinostat.

Conclusions: These results demonstrate a novel immunomodulatory effect of class I HDAC inhibition and provide a rationale for the clinical testing of entinostat to enhance cancer immunotherapy.

Publication types

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

MeSH terms

  • Acetylation / drug effects
  • Animals
  • Benzamides / pharmacology
  • Benzamides / therapeutic use*
  • CD8-Positive T-Lymphocytes / immunology
  • Carcinoma, Renal Cell / drug therapy*
  • Carcinoma, Renal Cell / genetics
  • Carcinoma, Renal Cell / immunology
  • Carcinoma, Renal Cell / pathology
  • Castration
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Down-Regulation / drug effects
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism
  • Gene Expression Regulation, Neoplastic / drug effects
  • Histone Deacetylase Inhibitors / pharmacology
  • Histone Deacetylase Inhibitors / therapeutic use*
  • Histone Deacetylases / metabolism*
  • Humans
  • Immunity / drug effects
  • Immunotherapy*
  • Interferon-gamma / immunology
  • Interleukin-2 / therapeutic use
  • Kidney Neoplasms / drug therapy
  • Kidney Neoplasms / genetics
  • Kidney Neoplasms / immunology
  • Kidney Neoplasms / pathology
  • Lymphocyte Depletion
  • Male
  • Mice
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / immunology
  • Prostatic Neoplasms / pathology
  • Pyridines / pharmacology
  • Pyridines / therapeutic use*
  • STAT3 Transcription Factor / metabolism
  • T-Lymphocytes, Regulatory / drug effects
  • T-Lymphocytes, Regulatory / immunology*
  • Vaccines, Subunit / immunology
  • Vaccines, Subunit / therapeutic use

Substances

  • Benzamides
  • Forkhead Transcription Factors
  • Foxp3 protein, mouse
  • Histone Deacetylase Inhibitors
  • Interleukin-2
  • Pyridines
  • STAT3 Transcription Factor
  • Vaccines, Subunit
  • entinostat
  • Interferon-gamma
  • Histone Deacetylases