Treatment of tumors with vitamin E suppresses myeloid derived suppressor cells and enhances CD8+ T cell-mediated antitumor effects

PLoS One. 2014 Jul 29;9(7):e103562. doi: 10.1371/journal.pone.0103562. eCollection 2014.

Abstract

Vitamin E has been shown to have strong anticarcinogenic properties, including antioxidant characteristics, making it an ideal candidate for use in combination with immunotherapies that modify the tumor microenvironment. The tumor microenvironment contains immunosuppressive components, which can be diminished, and immunogenic components, which can be augmented by immunotherapies in order to generate a productive immune response. In the current study, we employ the α-tocopherol succinate isomer of vitamin E to reduce immunosuppression by myeloid derived suppressor cells (MDSCs) as well as adoptive transfer of antigen-specific CD8+ T cells to generate potent antitumor effects against the HPV16 E7-expressing TC-1 tumor model. We show that vitamin E alone induces necrosis of TC-1 cells and elicits antitumor effects in TC-1 tumor-bearing mice. We further demonstrate that vitamin E reverses the suppression of T cell activation by MDSCs and that this effect is mediated in part by a nitric oxide-dependent mechanism. Additionally, treatment with vitamin E reduces the percentage of MDSCs in tumor loci, and induces a higher percentage of T cells, following T cell adoptive transfer. Finally, we demonstrate that treatment with vitamin E followed by E7-specific T cell adoptive transfer experience elicits potent antitumor effects in tumor-bearing mice. Our data provide additional evidence that vitamin E has anticancer properties and that it has promise for use as an adjuvant in combination with a variety of cancer therapies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CD11b Antigen / metabolism
  • CD8-Positive T-Lymphocytes / cytology
  • CD8-Positive T-Lymphocytes / drug effects*
  • CD8-Positive T-Lymphocytes / immunology
  • Disease Models, Animal
  • Female
  • Immunotherapy, Adoptive
  • Mice
  • Mice, Inbred C57BL
  • Myeloid Cells / cytology
  • Myeloid Cells / drug effects*
  • Myeloid Cells / metabolism
  • Necrosis
  • Neoplasms / immunology
  • Neoplasms / pathology
  • Neoplasms / therapy
  • Nitric Oxide / chemistry
  • Nitric Oxide / toxicity
  • Papillomavirus E7 Proteins / immunology
  • Papillomavirus E7 Proteins / metabolism
  • alpha-Tocopherol / pharmacology*
  • alpha-Tocopherol / therapeutic use

Substances

  • CD11b Antigen
  • Papillomavirus E7 Proteins
  • oncogene protein E7, Human papillomavirus type 16
  • Nitric Oxide
  • alpha-Tocopherol