Treatment of glioblastoma multiforme using a combination of small interfering RNA targeting epidermal growth factor receptor and β-catenin.

BACKGROUND: Epidermal growth factor receptor (EGFR) and β-catenin are two key mediators of cell signal transduction implicated in the pathogenesis of a variety of tumors. There is emerging evidence indicating that they are overexpressed in glioblastoma multiforme (GBM) and both play significant roles in GBM carcinogenesis. Moreover, down-regulating EGFR individually only provides limited therapeutic efficacy. Therefore, we aimed to determine the feasibility and efficacy of gene therapy of GBM using combinatorial inhibition of EGFR and β-catenin in view of the cross-talk between these two signaling pathways.
METHODS: The down-regulatory effect of small interfering RNA (siRNA) targeting EGFR and β-catenin alone or in combination in human GBM cells U-87 MG was evaluated by Quantitative RT-PCR. Cell proliferation in the short- and long-term was investigated by alamar blue and clonogenic assays, respectively. An annexin-V assay was performed to detect apoptosis caused by siRNA treatment. The effect of downregulating EGFR and β-catenin on cell cycle progression, cell migration and invasive potential were also examined.
RESULTS: The siRNA treatment potently reduced gene expression of EGFR and β-catenin at the mRNA level. Simultaneous inhibition of EGFR and β-catenin greatly decreased GBM cell proliferation. Although no significant increase in apoptosis was demonstrated, combinatorial siRNA treatment delayed the progression of cell cycle with an increased proportion of cells arrested in the G0/1 phase. Furthermore, EGFR and β-catenin siRNA in combination significantly inhibited the migratory and invasive ability of GBM cells.
CONCLUSIONS: Simultaneous inhibition of EGFR and β-catenin expression could represent an effective therapy for human GBM, and warrants further study in vivo.