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CDK4 regulation by TNFR1 and JNK is required for NF-kappaB-mediated epidermal growth control

Jennifer Y Zhang1, Shiying Tao, Robin Kimmel

  • 1Veterans Affairs Palo Alto Healthcare System, Palo Alto, CA 94304, USA.

The Journal of Cell Biology
|February 9, 2005
PubMed

Insights

Nuclear factor kappaB (NF-kappaB) normally inhibits skin cell growth. Loss of NF-kappaB function leads to skin hyperplasia by increasing CDK4, a key cell cycle regulator.

Area of Science:

  • Dermatology
  • Molecular Biology
  • Oncology

Background:

  • Nuclear factor kappaB (NF-kappaB) plays a crucial role in maintaining epidermal homeostasis by inhibiting cell proliferation.
  • Dysregulation of NF-kappaB signaling is implicated in skin oncogenesis and uncontrolled cell growth.

Purpose of the Study:

  • To elucidate the molecular mechanisms by which NF-kappaB loss promotes epidermal proliferation and oncogenesis.
  • To identify key regulators involved in NF-kappaB-mediated control of epidermal growth.

Main Methods:

  • Utilized three distinct genetic approaches to impair NF-kappaB function in the epidermis, including conditional NF-kappaB blockade.
  • Investigated the expression and tissue distribution of the G1 cell cycle kinase, CDK4, in response to NF-kappaB inhibition.
  • Examined the requirement of TNFR1 and c-Jun NH2-terminal kinase (JNK) signaling in CDK4 up-regulation.
  • Assessed the role of CDK4 in epidermal growth deregulation using Cdk4 gene deletion.

Main Results:

  • Impairment of NF-kappaB function in the epidermis led to significant epidermal hyperplasia.
  • Increased protein levels and tissue distribution of CDK4 were observed in conjunction with epidermal hyperplasia.
  • CDK4 up-regulation was dependent on intact TNFR1 and JNK signaling pathways.
  • Conditional NF-kappaB blockade combined with Cdk4 gene deletion confirmed CDK4's essential role in mediating growth deregulation.

Conclusions:

  • Epidermal homeostasis is maintained through the antagonistic regulation of CDK4 expression by NF-kappaB and the TNFR1/JNK pathway.
  • NF-kappaB acts as a suppressor of CDK4, while TNFR1/JNK signaling promotes its expression.
  • Understanding this regulatory balance is critical for comprehending skin growth control and developing therapeutic strategies for oncogenesis.

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