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Profiling the downstream genes of tumor suppressor PTEN in lung cancer cells by complementary DNA microarray
1Institute of Biomedical Sciences, Academia Sinica, National Health Research Institute, Graduate Institute of Molecular Biology, College of Medicine, National Taiwan University, Taipei.
Abstract:
The phosphatase and tensin homology deleted on chromosome 10 (PTEN) is a tumor suppressor gene with sequence homology to tyrosine phosphatases and the cytoskeletal proteins tensin and auxilin. PTEN has recently been shown to inhibit cell migration and the spreading and formation of focal adhesions. This study investigated the role of PTEN in carcinoma invasion in a lung-cancer cell line and examined the downstream genes regulated by PTEN. We have previously established a cell-line model in human lung adenocarcinoma with different invasive abilities and metastatic potentials. Examining PTEN gene expression in these cell lines, we found that a homozygous deletion in exon 5 is associated with high invasive ability. We then constructed stable constitutive and inducible wild-type PTEN-overexpressed transfectants in the highly invasive cell line CL(1-5). We found that an overexpression of PTEN can inhibit invasion in lung cancer cells. To further explore the downstream genes regulated by PTEN, a high-density complementary DNA (cDNA) microarray technique was used to profile gene changes after PTEN overexpression. Our results indicate a panel of genes that can be modulated by PTEN. PTEN overexpression downregulated genes, including integrin alpha(6), laminin beta(3), heparin-binding epidermal growth factor-like growth factor, urokinase-type plasminogen activator, myb protein B, Akt2, and some expressed sequence tag (EST) clones. In contrast, PTEN overexpression upregulated protein phosphatase 2A1B, ubiquitin protease (unph), secreted phosphoprotein 1, leukocyte elastase inhibitor, nuclear factor-kappaB, cyclic adenosine monophosphate response element binding protein, DNA ligase 1, heat shock protein 90, and some EST genes. Northern hybridization and flow cytometry analysis also confirmed that PTEN overexpression results in the reduced expression of the integrin alpha(6) subunit. The results of this study indicate that PTEN overexpression may inhibit lung cancer invasion by downregulation of a panel of genes including integrin alpha(6). The cDNA microarray technique may be an effective tool to study the downstream function of a tumor suppressor gene.
Insights
Overexpressing the PTEN tumor suppressor gene inhibits lung cancer cell invasion. This occurs by downregulating genes like integrin alpha(6), identified using cDNA microarray analysis.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- The PTEN gene acts as a tumor suppressor, inhibiting cell migration and focal adhesion formation.
- PTEN's role in carcinoma invasion and its downstream regulatory targets remain areas of investigation.
Purpose of the Study:
- To investigate the function of PTEN in lung carcinoma cell invasion.
- To identify downstream genes regulated by PTEN in lung cancer.
Main Methods:
- Utilized a human lung adenocarcinoma cell-line model with varying invasive potentials.
- Employed stable PTEN-overexpressed transfectants and high-density cDNA microarray analysis.
- Confirmed gene expression changes using Northern hybridization and flow cytometry.
Main Results:
- Homozygous deletion in PTEN exon 5 correlated with high invasive ability in lung cancer cells.
- PTEN overexpression significantly inhibited lung cancer cell invasion.
- Identified multiple genes downregulated (e.g., integrin alpha(6)) and upregulated by PTEN overexpression.
Conclusions:
- PTEN overexpression inhibits lung cancer invasion, potentially through the downregulation of genes like integrin alpha(6).
- cDNA microarray analysis is an effective method for studying tumor suppressor gene functions.