No abstract

Inhibition of microRNA-21 (miR-21) has been shown to promote apoptosis of cancer cells and to reduce tumor size in glioblastoma. However, efficient carriers for antisense-oligodeoxynucleotide (antisense-ODN) against miR-21 have not yet been developed. In this study, the R3V6 peptide (R3V6) was evaluated as a carrier of antisense-ODN. In a gel retardation assay, R3V6 formed a complex with an antisense-ODN. The serum stability assay showed that R3V6 protected it from nucleases more efficiently than polyethylenimine (PEI; 25 kDa, PEI25k). A Renilla luciferase gene with a 3'-untranslated region (3'-UTR) recognizable by miR-21 (psiCHECK2-miR-21-UTR) was constructed for the antisense-ODN assay. psiCHECK2-miR-21-UTR expressed less Renilla luciferase in the cells with a higher level of miR-21 due to the effect of miR-21. In an in vitro transfection assay, the R3V6 peptide delivered anti-miR-21 antisense-ODN into cells more efficiently than PEI (25 kDa, PEI25k) and lipofectamine. As a result, antisense-ODN/R3V6 complex inhibited miR-21 and increased Renilla luciferase expression more efficiently than antisense-ODN/PEI25k or antisense-ODN/Lipofectamine complexes in both C6 and A172 glioblastoma cells. Furthermore, the antisense-ODN/R3V6 complexes reduced the level of miR-21 and induced apoptosis of glioblastoma cells. These results suggest that the R3V6 peptide may be a useful carrier of antisense-ODN for glioblastoma gene therapy.

Combined delivery of chemical drug and therapeutic gene has been introduced as an efficient method for the treatment of cancers such as glioblastoma. In this study, bis-chloroethylnitrosourea (BCNU) and vascular endothelial growth factor (VEGF) small interfering RNA (VEGF-siRNA) were co-delivered into C6 glioblastoma cells using a non-toxic peptide-based carrier. The R3V6 peptides, which are composed of 3-arginine and 6-valine, formed self-assembled micelles in aqueous solution. BCNU, a hydrophobic anti-cancer drug, was loaded into the hydrophobic core of the micelles, forming BCNU-loaded R3V6 micelles (R3V6-BCNU). In gel retardation assay, R3V6-BCNU formed a stable complex with siRNA. In vitro transfection assay showed that the VEGF-siRNA/R3V6-BCNU complex had the highest transfection efficiency into C6 cells at a 1:20 weight ratio (VEGF-siRNA:R3V6-BCNU). In addition, the VEGF-siRNA/R3V6-BCNU complexes had higher delivery efficiency than lipofectamine or naked siRNA. VEGF expressions were remarkably decreased by transfection of the VEGF-siRNA/R3V6 or VEGF-siRNA/R3V6-BCNU complexes. Furthermore, R3V6-BCNU delivered BCNU more efficiently into the cells than BCNU only. Therefore, R3V6 delivered both VEGF-siRNA and BCNU efficiently into the glioblastoma cells. The results suggest that R3V6-BCNU may be useful for combined delivery of siRNA and chemical drug into cancer cells.

MicroRNA-21 (miR-21) expression in glioblastoma inhibits the expression of pro-apoptotic genes, thereby promoting tumor growth. A previous study showed that the amphiphilic R3V6 peptide is an efficient carrier of the anti-miR-21 antisense oligodeoxynucleotide (antisense-ODN) into cells in vitro. In the current study, in vivo delivery of antisense-ODN using the R3V6 peptide was evaluated in a glioblastoma animal model. In vitro transfection showed that the R3V6 peptide delivered antisense-ODN more efficiently than polyethylenimine (25 kDa, PEI25k) in C6 glioblastoma cells. For in vivo evaluation, antisense-ODN/R3V6 complex was injected intratumorally into a C6 glioblastoma xenograft animal model. Tumor growth was suppressed by the injection of the antisense-ODN/R3V6 complex, compared with the antisense-ODN/PEI25k and scrambled-antisense-ODN (scr-antisense-ODN)/R3V6 complexes. Real-time RT-PCR showed that miR-21 levels were reduced most efficiently by the antisense-ODNR3V6 complex in tumors. Due to inhibition of miR-21, expression of the programed cell death 4 (PDCD4) gene was promoted in tumors, resulting in the induction of apoptosis of tumor cells. These results suggest that delivery of antisense-ODN using R3V6 peptides may be useful for the development of antisense-ODN therapy for glioblastoma.

No abstract