Preparation and in vitro evaluation of prostate cancer exosomes containing melittin / 中国药理学通报

ABSTRACT

Aim To prepare prostate cancer exosomes containing melittin and observe their uptake by prostate cancer cells. Methods Cells treated with starvation for different time were screened for exosome extraction. Exosomes from PC-3 cells were extracted by ultracentrifugation, and the extracted particles were examined by transmission electron microscopy, nanoparticle tracking analyzer(NTA), and Western blot. Melittin exosome system was prepared by repeated freeze-thaw method, incubation at room temperature as well as electroporation, and the size of encapsulation efficiency was measured by centrifugation. A high-performance liquid chromatography(HPLC)method was applied to assay the content of melittin exosomes(exo-mel). Fluorescence inverted microscopy was employed to evaluate the uptake of melittin exosomes by PC-3 cells, DU145 cells as well as LNCaP cells. Results The results of starvation treatment showed that 24 h starvation treatment was the optimal time point. TEM results showed that the exosomes were round or oval in shape with a distinct membranous structure, and the diameter was around 100 nm. The reagent protein concentration for NTA analysis of exosomes was 0.222 g·L-1. The results of Western blot for the marker proteins of exosomes showed that Alix and CD63 were positively expressed, which indicated that the exosomes could be obtained by starvation culture of PC-3 cells and ultracentrifugation. The results of entrapment efficiency showed that the entrapment efficiency of electroporation method was 17.51% ± 2.39%, that of repeated freeze-thaw method was 11.46% ± 1.02%, and that of room temperature incubation method was 3.93% ± 2.44%. The encapsulation efficiency of electroporation was the highest with significant difference(P<0.05). The uptake assay showed that PC-3 cells could efficiently take up exo-mel in a time-dependent manner, and DU145 cells and LNCaP cells also could take up exo-mel over time. Conclusions Exosomes can be accessed by starvation treatment and high-speed centrifugation, and the prostate cancer melittin exosome system prepared by electroporation method could be taken up by prostate cancer cells.