Experimental Model for Gene Therapy of Malignant Glioma

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Several malignant gliomas revealed EGFR gene amplification with a deletional mutation from exon 2 to exon 7. The overexpression of the aberrant EGFR gene is involved in the progression or pathogenesis of malignant glioma. The aberrant EGFR mRNA contains the -GUA- sequence at the junction between exon 1 and exon 8. A hammerhead ribozyme targeting the -GUA- site was prepared. The ribozyme (abEGFR-rib) cleaved the synthetic aberrant EGFR-RNA substrate in vitro. The abEGFR-rib also cleaved the substrate at the condition reflecting the physiological magnesium concentration (<2.5mM) and temperature (37ﾟC). The disabled ribozyme with a point mutation at the hammer head structure did not cleave the aberrant EGFR-RNA substrate at the same condition. The abEGFR-rib did not cleave the normal EGFR-RNA substrate (exon 1-exon 2). These findings suggest that the abEGFR-rib can specifically cleave the aberrant EGFR-RNA in vitro. The aberrant EGFR mRNA was expressed on a limited number of malignant glioma cells. The molecule was not expressed in the normal brain tissue. The ribozyme mediated aberrant EGFR mRNA cleavage should be useful for the malignant-glioma-specific anti-oncogene therapy.