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Regulation of C-myc and C-Ha-ras oncogene expression by cell shape

R E Farrell1, J J Greene

  • 1Department of Biology, Catholic University of America, Washington, DC 20064.

Journal of Cellular Physiology
|November 11, 1992
PubMed

Insights

Cell shape significantly impacts proto-oncogene expression in normal cells, affecting proliferation. Malignant cells show no such shape-dependent regulation, highlighting a key difference in growth control.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Oncology

Background:

  • Cell shape is a critical factor influencing cellular behavior and function.
  • Proto-oncogenes play a vital role in cell growth and proliferation.
  • Contact inhibition is a phenomenon where normal cells stop dividing when they come into contact with each other.

Purpose of the Study:

  • To investigate the influence of cell shape on proto-oncogene expression in normal and malignant human cells.
  • To determine the relationship between cell shape, proliferation, and the expression of specific oncogenes (c-myc, c-ras, c-fos, c-fes).
  • To elucidate the regulatory mechanisms underlying shape-dependent gene expression and cell growth control.

Main Methods:

  • Cells were cultured on surfaces with varying concentrations of poly(2-hydroxyethyl methacrylate) (poly[HEMA]) to control cell shape (degree of roundness).
  • Proliferation capacity was assessed in normal (CUA-1 fibroblasts, HT-IFNr) and malignant (HT-1080) cells.
  • mRNA levels of c-myc, c-ras, c-fos, and c-fes were analyzed using Northern blotting.
  • Transcription rates were quantified using the nuclear run-off assay.

Main Results:

  • Normal cells (CUA-1) exhibited shape-dependent proliferation, ceasing division upon reaching a critical roundness.
  • Expression of c-myc and c-ras oncogenes was highly sensitive to cell shape in normal cells, declining with increased roundness.
  • Malignant (HT-1080) and variant (HT-IFNr) cells showed proliferation independent of cell shape and lacked shape-dependent regulation of c-myc and c-ras.
  • c-fos and c-fes oncogene expression was independent of cell shape in all cell types tested.
  • Shape modulation of c-myc and c-ras expression occurred at the transcriptional level.

Conclusions:

  • Cell shape is a significant regulator of specific proto-oncogene expression (c-myc, c-ras) and proliferation in normal cells.
  • Loss of shape-dependent regulation of c-myc and c-ras is associated with malignant transformation and loss of contact inhibition.
  • While altered oncogene regulation contributes to uncontrolled growth, it is not the sole factor releasing cells from contact inhibition.

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