Self-assembled redox-responsive BRD4 siRNA nanoparticles: fomulation and its in vitro delivery in gastric cancer cells

With the development of newer biomarkers in the diagnosis of gastric cancer (GC), therapeutic targets are emerging and molecular-targeted therapy is in progress RNA interference has emerged as a promising method of gene targeting therapy. However, naked small interfering RNA (siRNA) is unstable and susceptible to degradation, so employing vectors for siRNA delivery is the focus of our research. Therefore, we developed LMWP modified PEG-SS-PEI to deliver siRNA targeting BRD4 (L-NPs/siBRD4) for GC therapy. L-NPs/siBRD4 were prepared by electrostatic interaction and characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The release characteristics, cellular uptake and intracellular localization were also investigated. The in vitro anticancer activity of the prepared nanoparticles was analysed by MTT, Transwell invasion and wound healing assay. Quantitative real time-polymerase chain reaction (qRT-PCR) and Western blot were used to detect the effect of gene silencing. The results showed that the optimal N/P was 30 and the prepared L-NPs/siBRD4 uniformly distributed in the system with a spherical and regular shape. L-NPs/siBRD4 exhibited an accelerated release in GSH-containing media from 12h to 24h. The uptake of L-NPs/siBRD4 was enhanced and mainly co-localized in the lysosomes. After 6h incubation, LMWP modified PEG-SS-PEI helped siRNA escape from the lysosomes and diffused into the cytoplasm. L-NPs/siBRD4 significantly inhibited the proliferation, migration and invasion of cells. This might be related with the silence of BRD4, then inhibition of PI3K/Akt and c-Myc. Our results demonstrate that L-NPs/siBRD4 are a novel delivery system with anticancer, which may provide a more effective strategy for GC treatment.