Enhanced expression of the urokinase-type plasminogen activator gene and reduced colony formation in soft agar by ectopic expression of PU.1 in HT1080 human fibrosarcoma cells

Abstract

Summary To investigate the cell biological function of PU.1, a member of the Ets family of transcription factors, a vector capable of expressing the protein was transfected into HT1080 human fibrosarcoma cells. Exogenous expression of PU.1 in HT1080 cells reduced colony-forming efficiency but stimulated cell migration in soft agar, although it did not affect cell growth in adherent culture. Expression of the urokinase-type plasminogen activator (uPA) mRNA, which is known to be correlated with cell migration and invasion, was enhanced in PU. 1 transfectants compared with mock transfectants. Run-on analysis demonstrated that uPA transcription was unaffected by PU.1, suggesting that this enhancement mainly occurs at a post-transcriptional level. On the other hand, treatment of HT1080 cells with the synthetic glucocorticoid dexamethasone (DEX; 10-7 M) significantly reduced uPA gene expression at a transcriptional level. Furthermore, DEX inhibited cell migration in soft agar without affecting cell growth. These negative effects of DEX on uPA expression and cell migration were alleviated by the expression of PU.1 in HT1080 cells, whereas expression of the N-ras oncogene, which is responsible for maintenance of the transformed phenotypes in HT1080 cells, was unaffected by PU.1 expression or DEX treatment in the cells. Our results suggest that expression of PU.1 can stimulate uPA gene expression at the post-transcriptional level, which may subsequently lead to activation of cell motility and/or reduced cell-cell adhesion, but reduces anchorage-independent growth of HT1080 cells.

Transforming Growth Factor-β1 Produced by Ovarian Cancer Cell Line HRA Stimulates Attachment and Invasion through an Up-regulation of Plasminogen Activator Inhibitor Type-1 in Human Peritoneal Mesothelial Cells

“…In our cell-cell interaction system, we found that uPA may inhibit cell adhesion but enhance cancer cell invasion through mesothelial cell layers. These findings may be supported by the fact that enhanced uPA expression leads to activation of cell motility but reduced cell-cell adhesion (35). The anti-uPA antibody 3689 used in the experiment shown in Fig.…”

ETS transcription factors: Possible targets for cancer therapy

“…We also reported that expression of the uPA gene was augmented by exogenous expression of PU.1 in HT1080 fibrosarcoma cells. 16) The region containing an ETS binding site adjacent to an AP1 binding site is called a Ras responsive element (RRE), since such elements are often found in the regulatory regions of the genes responsive to Ras signaling. 17) It has been reported recently that the promoter activity of MMP-7, highly expressed in colon cancer, is synergistically regulated by the PEA3 subfamily of ETS transcription factors and c-Jun, a component of AP1, in cooperation with β-catenin-LEF-1.…”

The role of Ets family transcription factor PU.1 in hematopoietic cell differentiation, proliferation and apoptosis

“…110 Although over-expression of PU.1 induced growth inhibition in MEL cells, it did not induce growth inhibition in a fibrosarcoma cell line grown in liquid culture, 11 suggesting that PU.1-induced growth arrest and apoptosis might be cell type-specific. Alternatively, PU.1 may exert different effects in different cellular states, which may explain why high levels of expression of PU.1 are not toxic in normal B cells and macrophages/ neutrophils.…”