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Cell cycle arrest and astrocytic differentiation resulting from PTEN expression in glioma cells
J Adachi1, K Ohbayashi, T Suzuki
1Department of Neurosurgery, Gunma University School of Medicine, Maebashi, Japan. jadachi@saitama-med.ac.jp
Object:
Genetic alterations of the PTEN gene (also known as MMAC1 or TEP1) have frequently been identified in high-grade gliomas, indicating that inactivation of PTEN plays a crucial role in human glioma progression. The aim of this study was to assess the biological significance of PTEN inactivation in the development of glioma.
Methods:
The authors introduced wild-type PTEN complementary DNA into four human glioma cell lines (T98G, U-251MG, U-87MG, and A172) containing endogenous aberrant PTEN alleles. The number of colonies transfected with the wild-type PTEN was reduced to 15 to 32% of those found after transfection of a control vector, suggesting growth suppression by the exogenous PTEN. To analyze phenotypic alterations produced by PTEN expression, T98G-derived clones with inducible PTEN expression were further established using a tetracycline-regulated inducible gene expression system. Induction of PTEN expression suppressed the in vitro growth of T98G cells with accumulation of G1 phase cells. Furthermore, when cells were cultured in the presence of the extracellular matrix (ECM), PTEN expression caused distinct morphological changes, with multiple and elongated cytoplasmic processes similar to those of normal astrocytes. The level of glial fibrillary acidic protein, an intermediate protein specifically expressed in differentiated astrocytes, was upregulated concomitantly.
Conclusions:
These findings strongly indicate that exogenous PTEN expression inhibits the proliferation of glioma cells by inducing G1 arrest and elicits astrocytic differentiation in the presence of the ECM. Inactivation of PTEN would play an important role in the enhancement of unregulated growth of undifferentiated glioma cells.
Insights
Restoring PTEN gene function in glioma cells suppressed their growth and promoted differentiation into astrocyte-like cells. PTEN inactivation is crucial for the aggressive growth of undifferentiated glioma.
Area of Science:
- Neuro-oncology
- Molecular Biology
- Cell Biology
Background:
- PTEN gene alterations are common in high-grade gliomas.
- PTEN inactivation is implicated in glioma progression.
Purpose of the Study:
- To investigate the biological role of PTEN inactivation in glioma development.
- To assess the effects of restoring PTEN function on glioma cells.
Main Methods:
- Introduced wild-type PTEN cDNA into human glioma cell lines.
- Established inducible PTEN expression in T98G cells using a tetracycline-regulated system.
- Analyzed phenotypic changes, cell cycle progression, and differentiation markers.
Main Results:
- Exogenous PTEN expression suppressed glioma cell proliferation and induced G1 cell cycle arrest.
- PTEN expression led to morphological changes resembling astrocytes in the presence of extracellular matrix.
- Upregulation of glial fibrillary acidic protein indicated astrocytic differentiation.
Conclusions:
- Restoring PTEN function inhibits glioma cell proliferation and promotes differentiation.
- PTEN inactivation contributes to the uncontrolled growth of undifferentiated glioma cells.