PLGA/poloxamer nanoparticles loaded with EPAS1 siRNA for the treatment of pancreatic cancer in vitro and in vivo.

Endothelial PAS domain protein 1 (EPAS1) is a hypoxia-inducible protein that contributes to tumor progression. Hypoxia is involved in tumor aggressiveness and resistance to chemotherapy and ionizing radiation. In this study, we aimed to assess the effects of EPAS1 silencing using polyethylenimine-poly(lactide-coglycolide) (PLGA)/poloxamer nanoparticles loaded with EPAS1 siRNA on BxPC-3 pancreatic cancer cells and in a mouse model of ectopic pancreatic cancer. PLGA/poloxamer nanoparticles loaded with EPAS1 siRNA or scramble siRNA were prepared using the emulsion/solvent evaporation method. BxPC-3 pancreatic cancer cells were cultured under hypoxic conditions and treated with or without the nanoparticles. MTT and apoptosis assays were then performed. A xenograft nude mouse model of pancreatic cancer was established and the mice were treated with or without the nanoparticles. The mRNA and protein expression levels of EPAS1 in the tumor tissues were determined by semi-quantitative RT-PCR and western blot analysis, respectively. Vascular endothelial growth factor (VEGF) and tumor microvessel density indicated by CD34 were determined by immunohistochemistry. The in vitro release of EPAS1 siRNA from the nanoparticles exerted a sustained-release effect. EPAS1 siRNA nanoparticles inhibited BxPC-3 cell proliferation, and induced cell apoptosis under hypoxic conditions, compared with the nanoparticles loaded with scramble siRNA (all P<0.05). EPAS1 expression was significantly decreased in the pancreatic tumors of the mice injected with the nanoparticles loaded with EPAS1 siRNA. The pancreatic tumors of the mice injected with nanoparticles loaded with EPAS1 siRNA were significantly smaller in size and had a lower number of microvessels and a percentage of VEGF-positive cells compared with those of the mice injected with the nanoparticles loaded with scramble siRNA (all P<0.05). In conclusion, the results from the present study suggest that PLGA/poloxamer nanoparticles loaded with EPAS1 siRNA inhibit pancreatic cancer cell proliferation, induce cell apoptosis under hypoxic conditions and significantly inhibit the formation of microvessels and tumor growth in vivo.