In vitro studies of polyethyleneimine coated miRNA microspheres as anticancer agents

RNA plays important roles as a gene-silencing agent, a therapeutic agent for clinical treatment, and in the differentiation, proliferation, and development of cells. However, RNA is very difficult to work with due to its sensitivity and fragility. Another obstacle in using RNA for gene delivery/silencing is its negative charge, which causes its repulsion by cell membranes, which are also negatively charged. Our recent study showed that miR-125b is upregulated in glioblastoma (GMB) and plays an oncogenic role in GMB cells by promoting cell proliferation and inhibiting apoptosis. Endogenous miR-125b can be blocked by transfection of its antisense RNA molecule, miR-125b antisense (miR-125b-AS). Thus, miR- 125b-AS can be developed as an RNA-based agent for cancer treatment. However, instability during storage and difficulty in delivery into cells has limited the use of RNA-based therapies thus far. In the current work, we demonstrate a short and simple one-step technique for the preparation of positively charged RNA nanospheres (miR-125b-RNS and miR-125b-AS-RNS) coated with a bioavailable polymer, polyethylenimine (PEI). These RNA nanospheres are able to penetrate the cell directly without the use of liposomes. Our study confirmed that converting miR-125b and miR-125b-AS into nanospheres is a viable approach for storing RNA. In addition, this study provides evidence that PEI-coated RNA nanospheres have the potential to be used as a novel class of anticancer agents.