Defective STAT1 activation associated with impaired IFN-γ production in NK and T lymphocytes from metastatic melanoma patients treated with IL-2

Oncotarget. 2016 Jun 14;7(24):36074-36091. doi: 10.18632/oncotarget.8683.

Abstract

High dose (HD) IL-2 therapy has been used for almost two decades as an immunotherapy for metastatic melanoma. IL-2 promotes the proliferation and effector function of T and NK cells through the tyrosine phosphorylation and activation of signal transducer and activator of transcription factors (STAT), especially STAT5. However, whether any defects in STAT activation exist in T and NK lymphocytes from melanoma patients are under debate. Here, we measured the extent of HD IL-2-induced phosphorylation of STAT5 and STAT1 in lymphocyte subsets from metastatic melanoma patients and healthy controls at a single cell level using flow cytometry. We found no defects in IL-2-induced STAT5 phosphorylation and induction of proliferation in T and NK cell subsets in vitro. This was confirmed by measuring ex vivo STAT5 activation in whole blood collected from patients during their first bolus HD IL-2 infusion. IL-2 also induced STAT1 phosphorylation via IFN-γ receptors in T and NK cell subsets through the release of IFN-γ by CD56hi and CD56lo NK cells. Further analysis revealed that melanoma patients had a sub-optimal STAT1 activation response linked to lower IL-2-induced IFN-γ secretion in both CD56hi and CD56low NK cell subsets. STAT1 activation in response to IL-2 also showed an age-related decline in melanoma patients not linked to tumor burden indicating a premature loss of NK cell function. Taken together, these findings indicate that, although STAT5 activation is normal in metastatic melanoma patients in response to IL-2, indirect STAT1 activation is defective owing to deficiencies in the NK cell response to IL-2.

Keywords: IFN-γ; NK cells; STAT1; high-dose IL-2; melanoma.

MeSH terms

  • Adult
  • Aged
  • Female
  • Flow Cytometry
  • Humans
  • Interferon-gamma / biosynthesis*
  • Interleukin-2 / therapeutic use*
  • Killer Cells, Natural / metabolism*
  • Male
  • Melanoma / drug therapy*
  • Melanoma / metabolism
  • Melanoma / pathology
  • Middle Aged
  • Neoplasm Metastasis
  • Phosphorylation / drug effects
  • STAT1 Transcription Factor / metabolism*
  • STAT5 Transcription Factor / metabolism
  • T-Lymphocytes / metabolism*

Substances

  • Interleukin-2
  • STAT1 Transcription Factor
  • STAT1 protein, human
  • STAT5 Transcription Factor
  • Interferon-gamma