The PI3K-AKT-mTOR-signaling pathway is frequently activated in
glioblastoma (GBM). Inhibition of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta (PIK3CB)/p110β (a PI3K catalytic
isoform) by RNAi substantially suppresses GBM growth with less toxicity to normal astrocytes. However, insufficient and non-specific
small interfering RNA (
siRNA) delivery may limit the efficacy of
RNAi-based therapies against GBM. Here we prepared a novel methoxy-modified PIK3CB
siRNA molecule (siPIK3CB) that was covalently conjugated to a [
cyclo(Arg-Gly-Asp-D-Phe-Lys)-Ahx]2-Glu-PEG-MAL (biRGD)
peptide, which selectively binds to
integrin αvβ3 receptors. The αvβ3-positive U87MG cell line was selected as a representative for GBM. An orthotopic GBM xenograft model based on
luciferase-expressing U87MG was established and validated in vivo to investigate bio-distribution and anti-tumor efficacy of biRGD-siPIK3CB. In vitro, biRGD-siPIK3CB specifically entered and silenced PIK3CB expression in GBM cells in an αvβ3 receptor-dependent manner, thus inhibiting cell cycle progression and migration and enhancing apoptosis. In vivo, intravenously injected biRGD-siPIK3CB substantially slowed GBM growth and prolonged survival by reducing
tumor viability with silencing PIK3CB expression. Furthermore, biRGD-siPIK3CB led to mild tubulointerstitial injury in the treatment of GBM without obvious hepatotoxicity, whereas co-infusion of
Gelofusine obviously alleviated this injury without compromising anti-
tumor efficacy. These findings revealed a great translational potential of biRGD-siPIK3CB conjugate as a novel molecule for GBM
therapy.