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Reduction of Ha-ras-induced cellular transformation by elevated expression of protein phosphatase type 2A

Z Baharians1, A H Schönthal

  • 1Department of Molecular Microbiology and Immunology, K. Norris Comprehensive Cancer Center, University of Southern California, Los Angeles 90033-1034, USA.

Molecular Carcinogenesis
|May 18, 1999
PubMed

Insights

Elevated levels of serine/threonine protein phosphatase type 2A (PP2A) enhance resistance to oncogene-induced cell transformation. This suggests PP2A acts as a tumor suppressor by inhibiting proto-oncogene expression, supporting its anti-cancer potential.

Area of Science:

  • Cellular Biology
  • Molecular Oncology
  • Signal Transduction

Background:

  • The function of serine/threonine protein phosphatase type 2A (PP2A) in cellular growth regulation remains unclear.
  • Previous studies using phosphatase inhibitors hinted at PP2A's potential anti-oncogenic properties, but direct evidence was lacking.

Purpose of the Study:

  • To investigate the impact of altered PP2A expression levels on cellular transformation induced by the Ha-ras oncogene.
  • To elucidate the molecular mechanisms underlying PP2A's role in oncogenesis.

Main Methods:

  • Utilized mouse fibroblasts engineered with varying PP2A expression levels.
  • Assessed focus formation induced by Ha-ras oncogene transfection.
  • Quantified Ha-ras-stimulated c-fos promoter activity.

Main Results:

  • Fibroblasts with increased PP2A expression exhibited significant resistance to Ha-ras-induced focus formation.
  • Elevated PP2A levels led to reduced Ha-ras-stimulated expression of the c-fos proto-oncogene promoter.
  • These molecular changes correlated with decreased cellular transformation.

Conclusions:

  • PP2A plays a negative regulatory role in cellular transformation.
  • The findings support the classification of PP2A as a tumor suppressor enzyme.
  • PP2A may exert its tumor-suppressive effects by modulating oncogenic signaling pathways, such as Ha-ras/c-fos.

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