p16(INK4a) inactivation is not required to immortalize human mammary epithelial cells

Oncogene. 2002 Nov 7;21(51):7897-900. doi: 10.1038/sj.onc.1205902.


Using standard culture conditions, primary human mammary epithelial cells (HMECs) undergo a premature, transient growth arrest termed M0 (mortality stage 0) after 10-15 population doublings in vitro. It has been reported that emergence from this growth arrest by the abrogation of p16(INK4a), a cyclin-dependent kinase inhibitor, and expression of the catalytic component of human telomerase (hTERT) are necessary for HMEC immortalization. Here we show that primary HMECs, grown on feeder layers, do not undergo this growth arrest and can be immortalized without abrogating p16. These findings support the concept that the so-called M0 stage represents a cell culture stress-induced growth arrest and that hTERT is sufficient to immortalize HMECs when cultured under adequate conditions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Breast / cytology*
  • Cell Culture Techniques / instrumentation
  • Cell Culture Techniques / methods
  • Cell Division / drug effects
  • Cell Transformation, Neoplastic / genetics*
  • Cells, Cultured / cytology
  • Cellular Senescence
  • Coculture Techniques
  • Culture Media, Serum-Free / pharmacology
  • Cyclin-Dependent Kinase Inhibitor p16 / physiology*
  • DNA-Binding Proteins
  • Epithelial Cells / cytology
  • Female
  • Gene Expression Profiling
  • Genes, Retinoblastoma
  • Genes, p16*
  • Humans
  • Mesoderm / cytology
  • Phosphorylation
  • Plastics
  • Protein Processing, Post-Translational
  • Retinoblastoma Protein / metabolism
  • Stress, Physiological
  • Telomerase / physiology*
  • Tumor Suppressor Protein p14ARF / biosynthesis
  • Tumor Suppressor Protein p14ARF / genetics


  • Culture Media, Serum-Free
  • Cyclin-Dependent Kinase Inhibitor p16
  • DNA-Binding Proteins
  • Plastics
  • Retinoblastoma Protein
  • Tumor Suppressor Protein p14ARF
  • Telomerase