Effective silencing of EGFR with RNAi demonstrates non-EGFR dependent proliferation of glioma cells.

The epidermal growth factor receptor (EGFR, ErbB1) is frequently dysregulated in a variety of solid human tumors, including malignant glioma. EGFR expression has been associated with disease progression, resistance to standard therapies and poor survival. The application of small interfering RNAs (siRNAs) has become an effective and highly specific tool to modulate gene expression, and a wide range of oncogenes have been silenced successfully. Here we show the siRNA-mediated down-regulation of EGFR in two established glioma cell lines with different EGFR expression levels (U373 MG, LN18). The expression of EGFR mRNA and protein was down-regulated by 70-90%. However, siRNA treatment had no inhibitory effect on cell proliferation, migration and activation status of EGFR-coupled signaling cascades. In accordance with these results, gene expression analysis with microarrays revealed only small, albeit specific changes in expression patterns. In conclusion, these data indicate that the specific down-regulation of EGFR might not be sufficient for a single agent therapeutic approach in malignant glioma.