Reversion of human glioblastoma malignancy by U1 small nuclear RNA/ribozyme targeting of scatter factor/hepatocyte growth factor and c-met expression.
BACKGROUND
Expression of scatter factor (SF), also known as hepatocyte growth factor (HGF), and its receptor, c-met, is often associated with malignant progression of human tumors, including gliomas. Overexpression of SF/HGF in experimental gliomas enhances tumorigenicity and tumor-associated angiogenesis (i.e., growth of new blood vessels). However, the role of endogenous SF/HGF or c-met expression in the malignant progression of gliomas has not been examined directly. In this study, we tested the hypothesis that human glioblastomas can be SF/HGF-c-met dependent and that a reduction in endogenous SF/HGF or c-met expression can lead to inhibition of tumor growth and tumorigenicity.


METHODS
Expression of the SF/HGF and c-met genes was inhibited by transfecting glioblastoma cells with chimeric transgenes consisting of U1 small nuclear RNA, a hammerhead ribozyme, and antisense sequences. The effects of reduced SF/HGF and c-met expression on 1) SF/HGF-dependent induction of immediate early genes (c-fos and c-jun), indicative of signal transduction; 2) anchorage-independent colony formation (clonogenicity), an in vitro correlate of solid tumor malignancy; and 3) intracranial tumor formation in immunodeficient mice were quantified. Statistical tests were two-sided.


RESULTS
Introduction of the transgenes into glioblastoma cells reduced expression of the SF/HGF and c-met genes to as little as 2% of control cell levels. Reduction in c-met expression specifically inhibited SF/HGF-dependent signal transduction (P<.01). Inhibition of SF/HGF or c-met expression in glioblastoma cells possessing an SF/HGF-c-met autocrine loop reduced tumor cell clonogenicity (P =.005 for SF/HGF and P=.009 for c-met) and substantially inhibited tumorigenicity (P<.0001) and tumor growth in vivo (P<.0001).


CONCLUSIONS
To our knowledge, this is the first successful inhibition of SF/HGF and c-met expression in a tumor model directly demonstrating a role for endogenous SF/HGF and c-met in human glioblastoma. Our results suggest that targeting the SF/HGF-c-met signaling pathway may be an important approach in controlling tumor progression.
Abounader
R
R
Department of Neuroscience and Kennedy Krieger Research Institute, Baltimore, MD 21205, USA.
Ranganathan
S
S
Lal
B
B
Fielding
K
K
Book
A
A
Dietz
H
H
Burger
P
P
Laterra
J
J
D000818:Animals; D015152:Blotting, Northern; D002448:Cell Adhesion; D002455:Cell Division; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D015316:Genetic Therapy; D005909:Glioblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D017228:Hepatocyte Growth Factor / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010641:Phenotype; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016372:RNA, Antisense / Q000235:genetics / Q000627:therapeutic use; D016337:RNA, Catalytic / Q000235:genetics* / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000235:genetics* / Q000627:therapeutic use; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000627:therapeutic use; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000187:drug effects
D016372:RNA, Antisense; D016337:RNA, Catalytic; D012334:RNA, Neoplasm; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met