These homologies suggest that PTEN may suppress tumor cell growth by antagonizing protein tyrosine kinases and may regulate tumor cell invasion and metastasis through interactions at focal adhesions.
These results suggest important roles of PTEN in the phenotype of tumor progression, and that the effects of PTEN on cell invasion, migration, and growth are mediated by distinct downstream pathways that diverge at the level of FAK.
PTEN inhibits cell migration and invasion by directly dephosphorylating two key tyrosine-phosphorylated proteins, thereby antagonizing interactions of integrins with the extracellular matrix and integrin-triggered signaling pathways.
We have also shown, by use of exogenously expressed PTEN and by treatment with the PI3'-kinase inhibitor LY294002, that ERBB-2-induced invasion is dependent on the PI3'-kinase pathway; however, PTEN does not dephosphorylate FAK in these cells.
Our present study is the first description of I3C that significantly inhibits the cell adhesion, spreading and invasion associated with an up-regulation of PTEN (a tumor suppressor gene) and E-cadherin (a regulator of cell-cell adhesion) expression in T47-D human breast cancer cells.
PTEN-independent induction of caspase-mediated cell death and reduced invasion by the focal adhesion targeting domain (FAT) in human astrocytic brain tumors which highly express focal adhesion kinase (FAK).
The recent findings that both phosphatidylinositol 3-kinase (PI 3-K) and the phosphatase and tensin homolog (PTEN) regulate tumor cell invasiveness have led the authors to surmise that these lipid signaling molecules might play a role in regulating matrix metalloproteinases (MMPs), which are essential for tumor cell invasion.
PTEN-staining status was not associated with patient age, International Federation of Gynecology and Obstetrics (FIGO) stage, myometrial invasion or histologic grade.
Restoration of the PTEN gene to invasive UM-UC-3 bladder tumour cells or expression of a dominant-negative version of the PI-3 kinase target, Akt, also potently inhibited invasion, indicating a central role for the PI-3 kinase/Akt pathway in this process.
To further establish the role of PTEN in tumor invasion, we evaluated vector- and PTEN-transfected T24T cells in an orthotopic in vivo assay that faithfully reproduces human disease.
We propose that the recruitment of PTEN at adherens junctions by MAGI-1b and the local down-regulation of phosphatidylinositol-3,4,5-trisphosphate pools and downstream effector systems at the site of cell-cell contacts are focal points for restraining both disruption of junctional complexes and induction of tumor cell invasion.
In conclusion, PTEN could inhibit cell invasion even in the presence of the constitutively active EGFR; this inhibition depended on its protein phosphatase activity, partially by dephosphorylating FAK, but not depended on its lipid phosphatase activity.
In a breast cancer cell line, I3C inhibited cell adhesion, spreading, and invasion associated with an upregulation of the tumor suppressor gene PTEN, suggesting that PTEN is important in inhibition of late stages in the development of cancer.
Infection of recombinant replication-defective adenovirus vector containing the wild-type PTEN cDNA (Ad5CMV-PTEN) significantly inhibited the cell migration and invasion activities of PTEN-mutated glioma cell lines in in vitro migration and chemoinvasion assays.
Modulation of miR-21 altered focal adhesion kinase phosphorylation and expression of matrix metalloproteases 2 and 9, both downstream mediators of PTEN involved in cell migration and invasion.
Furthermore, PTEN loss at the time of prostatectomy correlated with clinical parameters of more advanced disease, such as extraprostatic extension and seminal vesicle invasion.
Further addition of cell autonomous TGF-beta activation in the context of PTEN deficiency and Braf activation promoted dermal invasion in skin cultures without significantly promoting proliferation in vitro and in vivo.