In situ analysis of tumour specimens undergoing neovascularization show that the production of VEGF is specifically induced in a subset of glioblastoma cells distinguished by their immediate proximity to necrotic foci (presumably hypoxic regions) and the clustering of capillaries alongside VEGF-producing cells.
We observed EGFR gene amplification in astrocytomas and anaplastic astrocytomas with approximately the same incidence as in glioblastoma multiforme (33%), although large amplifications were only seen in glioblastoma multiforme.
A subpopulation of cells were present in the low-grade tumours that contained the same p53 gene mutation predominant in the cells of the recurrent tumours that had progressed to glioblastoma.
However, there is no evidence for GM-CSF production by glioblastoma cells in vivo: fresh tumor samples lack the mRNA for GM-CSF and the protein is not detectable in the tumor cyst fluids or the cerebrospinal fluids of glioblastoma patients.
Moreover, the presence of 15 cases of glioblastoma with loss of chromosome 10 but without EGFR gene amplification may further imply that the loss of a tumor suppressor gene (or genes) on chromosome 10 precedes EGFR gene amplification in glioblastoma tumorigenesis.
Our findings suggest that the amplification and/or overexpression either of EGFR or of the alpha PDGFR along with the coordinate overexpression of the beta PDGFR can contribute to the malignant phenotype of distinct subsets of human glioblastoma.
In experiments to identify molecules that might be important in the pathogenesis of glioblastoma multiforme, the most common malignant brain tumor, we found that annexin II (Lipocortin 2, p36), a likely second messenger in several different mitogenic pathways, was highly expressed in tumor tissue of glioblastoma multiforme (9 of 9) and highly anaplastic astrocytoma (2 of 6), but not in astrocytomas of lower pathological grade (0 of 6).
The more malignant histological features of anaplastic astrocytoma and glioblastoma multiforme appear to be reflected by a greater incidence of p53 accumulation.
The loss of sequences on chromosome 10 and the deletions of 9p (that is loss of tumor suppressor genes on these locations), and epidermal growth factor receptor gene amplification, have been proposed as sequential abnormalities participating in glioblastoma tumorigenesis.
LOH on chromosome 10 and p53 mutation were found together only in patients with glioblastoma multiforme (22%), suggesting that these genetic changes may accumulate during astrocytoma progression.
The specificity of the elevated transcription of TGF-alpha, TGF-beta, bFGF and flg in glioblastoma cell lines is further suggested by the fact that the transcription of the proto-oncogene c-erbB2, which is overproduced in breast tumor cell lines, was not elevated in glioblastoma cell lines.
The specificity of the elevated transcription of TGF-alpha, TGF-beta, bFGF and flg in glioblastoma cell lines is further suggested by the fact that the transcription of the proto-oncogene c-erbB2, which is overproduced in breast tumor cell lines, was not elevated in glioblastoma cell lines.
The specificity of the elevated transcription of TGF-alpha, TGF-beta, bFGF and flg in glioblastoma cell lines is further suggested by the fact that the transcription of the proto-oncogene c-erbB2, which is overproduced in breast tumor cell lines, was not elevated in glioblastoma cell lines.