The relationships of the amplification and gene expression of EGFR with tumor proliferating activity

Objective To study the distribution, expression and amplification of proto-oncogenes EGFR in human gliomas in China. Methods The gene expression of EGFR in 50 human gliomas, 2 malignant human glioma cell lines and 6 normal brain tissues were studied by immunohistochemical staining, Southern blot analysis and RT-PCR. The relationship between their expression was analysed, and their expression level correlated with glioma and proliferation activity was also studied. Results Immunohistochemical study showed EGFR expression rate was 70.59% (24/34) in high-grade gliomas, where it was 50% (8/16) in low grade gliomas. Both 2 malignant human cell lines expressed EGFR, and 6 normal brain samples had no EGFR protein expression. EGFR expression was significantly increased in ascending order from low to high grade gliomas. The results of RT-PCR analysis using a cDNA probe were coincident with that of immunohistochemical staining. EGFR gene amplification only existed in 1 case of human low grade gliomas(1/16) and one human malignant glioma cell line (1/2), but in 12 cases in human high grade gliomas(12/34). Comparing the immunostaining pattern of EGFR protein with the amplification of EGFR, we found a discrepancy between them. 14 cases manifested with EGFR gene overexpression without gene amplification. Conclusion EGFR over-expression is often observed in low grade glioma, which differs from the reports from most other Europe country and America, and there is a significant correlation with glioma grades. EGFR gene signaling pathways was associated with the proliferation activity in human gliomas. EGFR gene may play an important role in the malignant progression in gliomas.