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Nitric oxide inactivates the retinoblastoma pathway in chronic inflammation

Lei Ying1, Anne B Hofseth, Darren D Browning

  • 1Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, School of Medicine, University of South Carolina, Columbia, South Carolina 29208, USA.

Cancer Research
|October 3, 2007
PubMed

Insights

Nitric oxide (NO) species promote colon cancer in inflammatory bowel disease by inactivating the retinoblastoma protein (pRb), increasing cell proliferation. This NO-driven pathway offers potential targets for preventing inflammation-induced cancer.

Area of Science:

  • Gastroenterology
  • Molecular Biology
  • Cancer Research

Background:

  • Patients with chronic inflammatory bowel disease (IBD) face an elevated risk of colon cancer.
  • The specific molecular mechanisms driving colon cancer initiation and progression in IBD remain largely unknown.

Purpose of the Study:

  • To elucidate the molecular pathways linking inflammation to colon cancer in IBD.
  • To identify key molecules involved in the inflammation-to-cancer sequence.

Main Methods:

  • Utilized in vitro cell models and a mouse model of colitis.
  • Investigated the role of nitric oxide (NO) species in cellular proliferation and protein regulation.

Main Results:

  • Nitric oxide (NO) species were found to induce hyperphosphorylation and inactivation of the retinoblastoma protein (pRb).
  • This inactivation activates the pRb-E2F1 pathway, leading to increased cell proliferation.
  • NO-driven pRb hyperphosphorylation is mediated by soluble guanylyl cyclase/cyclic GMP signaling and involves MEK/ERK and PI3K/AKT pathways.

Conclusions:

  • Established a direct link between nitric oxide (NO) and the inactivation of retinoblastoma protein (pRb).
  • Identified specific signaling pathways (sGC/cGMP, MEK/ERK, PI3K/AKT) involved in NO-induced pRb inactivation.
  • Provided crucial insights into molecular targets for preventing colon cancer in the context of chronic inflammation.

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