Profiling the downstream genes of tumor suppressor PTEN in lung cancer cells by complementary DNA microarray

The phosphatase and tensin homology deleted on chromosome 10 (PTEN) is a tu mor 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-ca ncer 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 gen e expression in these cell lines, we found that a homozygous deletion in ex on 5 is associated with high invasive ability. We then constructed stable c onstitutive and inducible wild-type PTEN-overexpressed transfectants in the highly invasive cell line CL1-5. We found that an overexpression of PTEN c an inhibit invasion in lung cancer cells. To further explore the downstream genes regulated by PTEN, a high-density complementary DNA (cDNA) microarra y technique was used to profile gene changes after PTEN overexpression. Our results indicate a panel of genes that can be modulated by PTEN. PTEN over expression downregulated genes, including integrin alpha(6), laminin beta(3 ), heparin-binding epidermal growth factor-like growth factor, urokinase-ty pe plasminogen activator, myb protein B, Akt2, and some expressed sequence tag (EST) clones. In contrast, PTEN overexpression upregulated protein phos phatase 2A1B, ubiquitin protease (unph), secreted phosphoprotein 1, leukocy te elastase inhibitor, nuclear factor-kappa B, cyclic adenosine monophospha te response element binding protein, DNA ligase 1, heat shock protein 90, a nd 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 ov erexpression may inhibit lung cancer invasion by downregulation of a panel of genes including integrin alpha(6) The cDNA microarray technique may be a n effective tool to study the downstream function of a tumor suppressor gen e.