Related Experiment Video

Updated: Sep 22, 2025

LINE-1 Methylation Analysis in Mesenchymal Stem Cells Treated with Osteosarcoma-Derived Extracellular Vesicles
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NOS2 and S-nitrosothiol signaling induces DNA hypomethylation and LINE-1 retrotransposon expression

Christopher H Switzer1, Hyun-Ju Cho1, Thomas R Eykyn2

  • 1William Harvey Research Institute, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, London, EC1M 6BQ, United Kingdom.

Proceedings of the National Academy of Sciences of the United States of America
|May 18, 2022
PubMed

Insights

Inducible nitric oxide synthase (NOS2) causes DNA hypomethylation and genomic instability by degrading DNMT1. This epigenetic mechanism drives malignant epithelial transformation and poor breast cancer outcomes.

Area of Science:

  • Epigenetics
  • Cancer Biology
  • Molecular Oncology

Background:

  • Inducible nitric oxide synthase (NOS2) produces nitric oxide (NO), linked to inflammation, stress, and aggressive cancer phenotypes.
  • DNA hypomethylation, particularly of repeat elements, is an early carcinogenic event associated with genomic instability and retrotransposon activation.

Purpose of the Study:

  • To investigate the role of NOS2 and NO signaling in DNA methylation and cellular transformation.
  • To elucidate the molecular mechanisms by which NOS2 influences epigenetic modifications and drives cancer progression.

Main Methods:

  • Human cell line experiments to assess DNA methylation changes.
  • Correlation analysis of NOS2 expression with DNA methylation in human breast tumors.
  • Investigation of the NO/p38-MAPK/lysine acetyltransferase 5 pathway in DNMT1 degradation.

Main Results:

  • NOS2 expression and NO signaling induce significant DNA hypomethylation by promoting DNMT1 protein degradation.
  • NOS2 levels correlate with reduced DNA methylation and increased LINE-1 retrotransposon activity and DNA damage in breast tumors.
  • The NO/p38-MAPK/lysine acetyltransferase 5 pathway mediates DNMT1 degradation, which is essential for NO-induced epithelial transformation.

Conclusions:

  • NOS2 and NO signaling contribute to DNA damage and malignant epithelial transformation through an epigenetic mechanism involving DNMT1 degradation.
  • This pathway highlights a novel link between inflammation, epigenetics, and cancer progression, offering potential therapeutic targets.
Keywords:
DNA methylationNOS2S-nitrosationnitric oxideretrotransposon

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