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Growth suppression of glioma cells by PTEN requires a functional phosphatase catalytic domain
F B Furnari1, H Lin, H S Huang
1Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA 92093-0660, USA. ffurnari@ucsd.edu
Abstract:
Deletions of all or part of chromosome 10 are the most common genetic alterations in high-grade gliomas. The PTEN gene (also called MMAC1 and TEP1) maps to chromosome region 10q23 and has been implicated as a target of alteration in gliomas and also in other cancers such as those of the breast, prostate, and kidney. Here we sought to provide a functional test of its candidacy as a growth suppressor in glioma cells. We used a combination of Northern blot analysis, protein truncation assays, and sequence analysis to determine the types and frequency of PTEN mutations in glioma cell lines so that we could define appropriate recipients to assess the growth suppressive function of PTEN by gene transfer. Introduction of wild-type PTEN into glioma cells containing endogenous mutant alleles caused growth suppression, but was without effect in cells containing endogenous wild-type PTEN. The ectopic expression of PTEN alleles, which carried mutations found in primary tumors and have been shown or are expected to inactivate its phosphatase activity, caused little growth suppression. These data strongly suggest that PTEN is a protein phosphatase that exhibits functional and specific growth-suppressing activity.
Insights
The phosphatase and tensin homolog (PTEN) gene acts as a tumor suppressor in high-grade gliomas. Introducing functional PTEN into glioma cells with mutated PTEN inhibited their growth, confirming its suppressive role.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- High-grade gliomas frequently exhibit deletions in chromosome 10.
- The PTEN gene, located at 10q23, is a potential tumor suppressor implicated in various cancers.
Purpose of the Study:
- To functionally validate PTEN as a growth suppressor in glioma cells.
- To investigate the impact of PTEN mutations on glioma cell growth.
Main Methods:
- Northern blot analysis to assess gene expression.
- Protein truncation assays to evaluate protein function.
- Sequence analysis to identify PTEN mutations.
- Gene transfer to introduce wild-type and mutant PTEN.
Main Results:
- Introduction of wild-type PTEN suppressed growth in glioma cells with mutant PTEN alleles.
- Glioma cells with wild-type PTEN were unaffected by PTEN introduction.
- PTEN alleles with inactivating mutations showed minimal growth suppression.
Conclusions:
- PTEN functions as a specific growth suppressor in glioma cells.
- PTEN's growth-suppressing activity is linked to its phosphatase function.