Sp1 regulates expression of MET, and ribozyme-induced down-regulation of MET in fibrosarcoma-derived human cells reduces or eliminates their tumorigenicity

  • Authors:
    • Hongyan Liang
    • Sandra O'Reilly
    • Youhua Liu
    • Roger Abounader
    • John Laterra
    • Veronica M. Maher
    • J. Justin McCormick
  • View Affiliations

  • Published online on: May 1, 2004     https://doi.org/10.3892/ijo.24.5.1057
  • Pages: 1057-1067
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

Changes in expression of hepatocyte growth factor (HGF) and its receptor, MET, are associated with formation and malignant progression of human tumors. In the present study, 10 of 11 human fibrosarcoma cell lines tested expressed significantly higher levels of MET than were found in a series of normal human fibroblast lines. Still more significant, MET was constitutively phosphorylated in all 11 fibrosarcoma lines, whereas the normal fibroblasts exhibited very low levels of the phosphorylated form. All the cell lines expressed HGF mRNA. To determine the role of MET and/or HGF in tumorigenesis, a fibrosarcoma line expressing high levels of MET protein and low levels of HGF/NK2 mRNA was stably transfected with a hammerhead ribozyme targeting MET. In addition, a fibrosarcoma line expressing high levels of both MET protein and HGF/NK2 mRNA was transfected with a ribozyme targeting MET, or with a ribozyme targeting MET and another targeting HGF. The transfectant cell lines no longer formed tumors, or did so at a greatly reduced frequency and/or longer latency. Because Sp1 is a transcription factor for MET, we assayed the cell lines for their level of Sp1 protein. Sp1 was markedly overexpressed in 7 of the 11 fibrosarcoma lines compared to normal fibroblast lines. Deletion analysis and site-directed mutagenesis of the MET promoter revealed that tandem Sp1 sites in the proximal promoter are critical for transcription of MET. Increased expression of Sp1 in a normal human fibroblast line containing a MET promoter-luciferase construct resulted in a dose-dependent increase in luciferase. Conversely, inhibition of Sp1 binding to DNA in a fibrosarcoma cell line, using an Sp1 decoy, dramatically reduced MET expression. Taken together, these results indicate that in human fibrosarcoma cells, high levels of the phosphorylated form of MET are required for tumor formation and that Sp1 can function to control the level of MET.

Related Articles

Journal Cover

May 2004
Volume 24 Issue 5

Print ISSN: 1019-6439
Online ISSN:1791-2423

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
APA
Liang, H., O'Reilly, S., Liu, Y., Abounader, R., Laterra, J., Maher, V.M., & McCormick, J.J. (2004). Sp1 regulates expression of MET, and ribozyme-induced down-regulation of MET in fibrosarcoma-derived human cells reduces or eliminates their tumorigenicity. International Journal of Oncology, 24, 1057-1067. https://doi.org/10.3892/ijo.24.5.1057
MLA
Liang, H., O'Reilly, S., Liu, Y., Abounader, R., Laterra, J., Maher, V. M., McCormick, J. J."Sp1 regulates expression of MET, and ribozyme-induced down-regulation of MET in fibrosarcoma-derived human cells reduces or eliminates their tumorigenicity". International Journal of Oncology 24.5 (2004): 1057-1067.
Chicago
Liang, H., O'Reilly, S., Liu, Y., Abounader, R., Laterra, J., Maher, V. M., McCormick, J. J."Sp1 regulates expression of MET, and ribozyme-induced down-regulation of MET in fibrosarcoma-derived human cells reduces or eliminates their tumorigenicity". International Journal of Oncology 24, no. 5 (2004): 1057-1067. https://doi.org/10.3892/ijo.24.5.1057