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The OGF-OGFr axis utilizes the p16INK4a and p21WAF1/CIP1 pathways to restrict normal cell proliferation

Fan Cheng1, Patricia J McLaughlin, Michael F Verderame

  • 1Department of Neural and Behavioral Sciences, and Department of Medicine, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.

Molecular Biology of the Cell
|October 17, 2008
PubMed

Insights

Opioid growth factor (OGF) inhibits normal cell proliferation by activating cyclin-dependent kinase inhibitors p16(INK4a) and p21(WAF1/CIP1). Blocking these inhibitors prevents OGF

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Endocrinology

Background:

  • Opioid growth factor (OGF), an endogenous opioid peptide, acts as a negative regulator of normal cell proliferation.
  • The OGF receptor (OGFr) mediates OGF's growth-inhibitory effects.
  • The precise molecular mechanisms underlying OGF's inhibition of cell replication require further elucidation.

Purpose of the Study:

  • To investigate the role of the OGF-OGFr axis in regulating cell cycle activity in normal human cells.
  • To identify the specific cyclin-dependent kinase inhibitors (CKIs) involved in OGF-mediated growth inhibition.
  • To determine if p16(INK4a) and p21(WAF1/CIP1) are essential mediators of OGF's anti-proliferative effects.

Main Methods:

  • Utilized human umbilical vein endothelial cells (HUVECs) and human epidermal keratinocytes (NHEKs) as model systems.
  • Administered OGF peptide and measured effects on cell proliferation.
  • Assessed protein expression levels of various CKIs, including p16(INK4a), p21(WAF1/CIP1), p15, p18, p19, and p27.
  • Employed small interfering RNAs (siRNAs) to inhibit the activation of specific CKIs.

Main Results:

  • OGF significantly reduced cell proliferation in HUVECs and NHEKs by up to 40%.
  • OGF treatment upregulated the protein expression of p16(INK4a) and p21(WAF1/CIP1) in both cell types.
  • Inhibition of p16(INK4a) or p21(WAF1/CIP1) using siRNAs abolished the OGF-induced inhibition of cell proliferation.
  • Similar results were observed in human dermal fibroblasts and mesenchymal stem cells.

Conclusions:

  • The OGF-OGFr signaling pathway inhibits normal cell proliferation.
  • Both p16(INK4a) and p21(WAF1/CIP1) are critical mediators of OGF's anti-proliferative action.
  • These findings reveal a key molecular mechanism by which OGF regulates cell growth in normal tissues.

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