Co-delivery of EGFR and BRD4 siRNA by cell-penetrating peptides-modified redox-responsive complex in triple negative breast cancer cells

Aims: Triple negative breast cancer (TNBC) has drawn more and more attention due to its high mitotic indices, high metastatic rate and poor prognosis. Gene therapy, especially RNA interference (RNAi), has become a promising targeted therapy. However, improvement of transfection efficiency and discovery of target genes are major problems for the delivery of small interfering RNAs (siRNA). Materials and methods: In the present study, we developed GALA- and CREKA-modified PEG-SS-PEI to deliver siRNAs targeting on EGFR and BRD4 for TNBC therapy. The PEG-SS-PEI/siRNA complexes were prepared by electrostatic interaction and characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). The release characteristic, stability, cellular uptake and intracellular localization of the complexes were also studied. The effect of the complexes on cell viability was measured in MDA-MB-231 and HUVEC cells. The in vitro anti-tumor activities of the complexes were analyzed by Transwell invasion assay and wound healing assay. The gene silencing effect was evaluated by quantitative real time-polymerase chain reaction (qRT-PCR) and western blot. Key findings: The results revealed that the GALA- and CREKA-modified PEG-SS-PEI/siRNA complexes showed excellent transfection efficiency with redox-sensitive release profile and good biological compatibility. The complexes protected siRNA from the degradation of RNA enzymes. The complexes significantly inhibited the proliferation, invasion and migration of MDA-MB-231 cells via the synergistic inhibition of EGFR/PI3K/Akt and BRD4/c-Myc pathways. Significance: Taken together, co-delivery of siEGFR and siBRD4 by GALA-PEG-SS-PEI and CREKA-PEG-SS-PEI may provide a more effective strategy for the treatment of TNBC.