In primary glioblastomas and other tumor types, the epidermal growth factor receptor (EGFR) is frequently observed with alterations, such as amplification, structural rearrangements, or overexpression of the gene, suggesting an important role in glial tumorigenesis and progression. In this study, we investigated whether posttranscriptional gene silencing by vector-mediated RNAi to inhibit EGFR expression can reduce the growth of cultured human gli36 glioma cells. To "knock down" EGFR expression, we have created HSV-1-based amplicons that contain the RNA polymerase III-dependent H1 promoter to express double-stranded hairpin RNA directed against EGFR at two different locations (pHSVsiEGFR I and pHSVsiEGFR II). We demonstrate that both pHSVsiEGFR I and pHSVsiEGFR II mediated knock-down of transiently transfected full-length EGFR or endogenous EGFR in a dose-dependent manner. The knock-down of EGFR resulted in the growth inhibition of human glioblastoma (gli36-luc) cells both in culture and in athymic mice in vivo. Cell cycle analysis and annexin V staining revealed that siRNA-mediated suppression of EGFR induced apoptosis. Overall HSV-1 amplicons can mediate efficient and specific posttranscriptional gene silencing.
Bibliographical noteFunding Information:
We thank Mark I. Greene for the pMVEGFR-VSV plasmid, Yoshinaga Saeki for the ploxP-A-H6 plasmid, David Louis for the gli36 cells, and Kati Zlinszky for technical assistance. This work was supported in part by the Julius-Muller Foundation, the Swiss National Science Foundation (No. 3100A0-100195), the Cancer League of Kanton Zurich, and the 6th FW European Molecular Imaging Laboratories (EMIL)-NoE for Combating Cancer.
- HSV-1 amplicons
- Posttranscriptional gene silencing
- Tumor growth