Epidermal growth factor receptor (EGFR) gene amplification, mutations, and/or aberrant activation are frequent abnormalities in malignant gliomas and other human cancers and have been associated with an aggressive clinical course and a poor therapeutic outcome.
Epidermal growth factor receptor (EGFR) gene amplification is the most common genetic alteration in high-grade glioma, and approximately 50% of EGFR-amplified tumors also harbor a constitutively active mutant form of the receptor, DeltaEGFR.
Epidermal growth factor receptor (EGFR) gene amplification and protein expression in malignant gliomas (anaplastic astrocytoma, AA and glioblastoma, GBL) were suggested to be correlated with the degree of malignancy.
Epidermal growth factor receptor variant type III markedly accelerates angiogenesis and tumor growth via inducing c-myc mediated angiopoietin-like 4 expression in malignant glioma.
Alterations of the epidermal growth factor receptor (EGFR) occur frequently in malignant gliomas through gene amplification or rearrangement, especially in a large fraction of de novo type glioblastomas.
Although inhibition of the epidermal growth factor receptor is a plausible therapy for malignant gliomas that, in vitro, enhances apoptosis, the results of clinical trials have been disappointing.
Antisense epidermal growth factor receptor RNA transfection in human malignant glioma cells leads to inhibition of proliferation and induction of differentiation.
Because STAT signaling is commonly activated in malignant gliomas as a result of constitutive EGFR activation, strategies for inhibiting the EGFR/JAK/STAT cascade are of significant interest.
Different molecular biomarkers were identified by genetic studies and some of these are used in neuro-oncology for the evaluation of glioma patients, in particular combined deletions of the chromosome arms 1p and 19q in oligodendroglial tumors, methylation status of the O-6 methylguanine- DNA methyltransferase gene promoter and alterations in the epidermal growth factor receptor pathway in adult malignant gliomas, isocitrate dehydrogenase 1 (IDH1) and IDH2 gene mutations in diffuse gliomas, as well as BRAF status in pilocytic astrocytomas.
Expression analyses of miRNA overexpressing glioma cells and 3'-untranslated region luciferase reporter gene assays revealed evidence that these miRNAs post-transcriptionally regulate expression of glioma-relevant genes, including CDK6 (miR-107), EGFR (miR-146b-5p, miR-1287-5p), TERT and SEMA6A (miR-346), all of which are overexpressed in malignant gliomas in situ.
Furthermore, we found that STAT3 constitutive activation coexisted with EGFR expression in 27.2% of primary high-grade/malignant gliomas and such coexpression correlated positively with glioma grade.
Glioblastomas showed a significantly lower level of ganp mRNA than anaplastic astrocytomas, as measured by real-time reverse transcription-PCR, in 101 cases of adult MG. MGs of ganp(Low) expression displayed more malignant characteristics, with loss of heterozygosity on chromosome 10, epidermal growth factor receptor gene amplification, and significantly poorer prognosis than the ganp(High) group.
However, this correlation only reflected the higher percentages of cases with EGFR alterations in malignant gliomas and was not an independent prognostic factor as determined by multifactorial analysis.