Clinically, patients afflicted with ZM fusion harboring glioblastomas survived poorly relative to those afflicted with non-ZM-harboring sGBMs (P < 0.001).
In contrast to the classical subtype of primary glioblastoma, the cases studied here were characterized by the absence of EGFR amplification, PTEN loss, and 9p homozygous deletion and overexpression of p53, PDGFRα, and c-MET, suggesting that they can be classified as the proneural or mesenchymal subtype of glioblastoma and benefit from intensive therapy that includes temozolomide.
We also showed that Wnt/β-catenin signaling activities in GBM are directly modulated by the addition of ligand-mediated MET activation or MET inhibition.
Here, we review findings that associate MET expression and activity with a specific, genetically defined glioblastoma stem cell subtype, and data showing how MET sustains the stem cell phenotype in glioblastoma and other tumors.
MET gain was detected in primary glioblastomas (47%) and secondary glioblastomas (44%), suggesting that this genetic alteration plays a role in the pathogenesis of both glioblastoma subtypes.
We investigated the molecular factors and pathway activation signatures that determine sensitivity to c-MET inhibitors in a panel of glioblastoma and medulloblastoma cells, glioblastoma stem cells, and established cell line-derived xenografts using functional assays, reverse protein microarrays, and in vivo tumor volume measurements, but validation with animal survival analyses remains to be done.
In this study, we found that expression of the MET oncogene was associated with neurospheres expressing the gene signature of mesenchymal and proneural subtypes of glioblastoma.
This phenomenon is especially common among tumors with PDGFRA amplification: overall, 43% of PDGFRA-amplified GBM were found to have amplification of EGFR or the hepatocyte growth factor receptor gene (MET) as well.
These results indicate the possible existence of multiple mechanisms of MET activation in glioblastomas and that the activation system of proHGF/SF is important in progression of glioblastomas that express endogenous proHGF/SF and require ligand-dependent MET activation.
We investigated the effect of HGF/SF on matrix metalloproteinase-2 (MMP-2), membrane type 1 matrix metalloproteinase (MT1-MMP) and tissue inhibitors of metalloproteinases (TIMPs), expressions of c-Met/HGF receptor-positive human glioblastoma cells.
Although the extent of the amplified domain varied, the close vicinity of the MET gene was the only region consistently amplified in these glioblastomas.