Elevation of cell cycle control proteins during spontaneous immortalization of human keratinocytes

Robert H. Rice, Kathleen E. Steinmann, Lea Ann DeGraffenried, Qin Qin, Nancy Taylor, Robert Schlegel

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


A human line of spontaneously immortalized Keratinocytes (SIK cells) has been derived from ostensibly normal epidermis and has proven useful in dissecting molecular changes associated with immortalization. The original cultures had a normal karyotype and a colony forming efficiency of ∼3% through 10 passages. At passage 15, after which normal strains ordinarily senesce, these cells continued vigorous growth and gradually increased in colony forming efficiency, stabilizing at ∼30% by passage 40. During the early stage of increasing colony forming efficiency, the cells acquired a single i(6p) chromosomal aberration and 5-to 10-fold increases in expression of the cell-cycle control proteins cyclin A, cyclin B, and p34cdc2. Additional chromosomal aberrations accumulated at later passages (i(8q) and +7), but the i(6p) and the increased expression of cell-cycle proteins were maintained, raising the possibility that these features were important for immortalization. Regulation of cell growth and differentiation in the cultures appeared minimally altered compared with normal keratinocytes as judged by their microscopic appearance and generation of abortive colonies, sensitivity to growth suppression by transforming growth factor-β and tetradecanoylphorbol acetate, and dependence upon epidermal growth factor for progressive growth.

Original languageEnglish (US)
Pages (from-to)185-194
Number of pages10
JournalMolecular Biology of the Cell
Issue number2
StatePublished - 1993

ASJC Scopus subject areas

  • Cell Biology
  • Genetics
  • Molecular Biology


Dive into the research topics of 'Elevation of cell cycle control proteins during spontaneous immortalization of human keratinocytes'. Together they form a unique fingerprint.

Cite this