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Immortalization of human mammary epithelial cells is associated with inactivation of the p14ARF-p53 pathway

Vladimir A Shamanin1, Elliot J Androphy

  • 1Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.

Molecular and Cellular Biology
|February 18, 2004
PubMed

Insights

Inactivation of the p14ARF-p53 pathway is crucial for human mammary epithelial cell immortalization. HPV16 E6 protein inhibits this pathway through independent mechanisms, enabling long-term cell proliferation.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cellular Senescence

Background:

  • The ARF-p53 tumor suppressor pathway is known to cause immortalization of murine fibroblasts.
  • The function of this pathway in human epithelial cell immortalization remains unclear.
  • Human papillomavirus 16 (HPV16) E6 protein is implicated in cellular transformation.

Purpose of the Study:

  • To investigate the role of the p14ARF-p53 pathway in the immortalization of human mammary epithelial cells (MEC).
  • To determine the mechanisms by which HPV16 E6 affects p14ARF and p53 functionality.
  • To elucidate the requirements for long-term proliferation of MEC.

Main Methods:

  • Analysis of p14ARF and p53 expression and function in MEC immortalized by HPV16 E6, a p53 degradation-defective E6 mutant (Y54D), or hTERT.
  • Enforced expression of p14ARF in hTERT-immortalized MEC to assess senescence induction.
  • Evaluation of p53-dependent DNA damage response in E6Y54D-immortalized MEC.

Main Results:

  • HPV16 E6-immortalized MEC (E6-MEC) and E6Y54D-MEC maintain high p14ARF levels.
  • hTERT-immortalized MEC down-regulate p14ARF at late passages and are sensitive to p14ARF-induced senescence.
  • E6Y54D inhibits p14ARF-induced p53 activation independently of p53 degradation, suggesting distinct E6 functions.

Conclusions:

  • Long-term proliferation of human mammary epithelial cells necessitates the inactivation of the p14ARF-p53 pathway.
  • HPV16 E6 employs independent mechanisms to inhibit p53 degradation and disrupt p14ARF signaling.
  • Understanding these mechanisms provides insights into epithelial cell immortalization and cancer development.

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