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Cytokine-enhanced cytolytic activity of exosomes from NK Cells

Yutaka Enomoto1, Peng Li1, Lisa M Jenkins2

  • 1Laboratory of Molecular Immunology, Immunology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, 20892-1674, USA.

Cancer Gene Therapy
|July 28, 2021
PubMed

Insights

Cytokine stimulation enhances the tumor-killing ability of natural killer cell extracellular vesicles (NK-EVs). CD226 on NK-EVs is key to this enhanced cytotoxicity, independent of granzymes, and NK-EVs enter target cells via macropinocytosis.

Area of Science:

  • Immunology
  • Cell Biology
  • Extracellular Vesicles

Background:

  • Natural killer (NK) cells are crucial for immune surveillance against tumors and viral infections.
  • NK cells identify and eliminate abnormal cells through cell-cell interactions.
  • NK cell-derived extracellular vesicles (NK-EVs) show anti-tumor potential, but their properties and cytokine regulation are unclear.

Purpose of the Study:

  • To investigate the effect of cytokines IL-15 and IL-21 on the characteristics and cytotoxic capacity of NK-EVs.
  • To identify key molecules responsible for enhanced NK-EV cytotoxicity.
  • To elucidate the mechanism of NK-EV uptake by target cells.

Main Methods:

  • Human NK-92 cells were stimulated with IL-15 + IL-21.
  • NK-EVs were isolated and characterized.
  • Cytotoxic assays were performed using NK-EVs.
  • Mass spectrometry was used to analyze protein content under different cytokine conditions.
  • Knockout experiments and blocking antibodies were employed to identify key molecules.
  • Macropinocytosis was investigated as an uptake mechanism.

Main Results:

  • IL-15 + IL-21 stimulation enhanced the cytotoxic capacity of NK-EVs against tumor cells.
  • While granzyme B and H were enriched in NK-EVs, they were not essential for the enhanced cytotoxicity.
  • Mass spectrometry identified CD226 (DNAM-1) as enriched on NK-EVs upon IL-15 + IL-21 stimulation.
  • Blocking CD226 significantly reduced NK-EV cytolytic activity.
  • NK-EVs were observed to be taken up by target cells through macropinocytosis.

Conclusions:

  • Cytokine stimulation, specifically IL-15 + IL-21, significantly enhances the anti-tumor cytotoxicity of NK-EVs.
  • CD226 on NK-EVs is a critical mediator of this enhanced cytotoxic effect, independent of granzymes.
  • NK-EVs utilize macropinocytosis for uptake into target cells, revealing a novel mechanism of action.

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