Development of synthetic microRNA‐214 showing enhanced cytotoxicity and RNase resistance for treatment of canine hemangiosarcoma

MicroRNA-214 (miR-214), a pivotal tumour-suppressive miRNA, is downregulated in canine hemangiosarcoma (HSA) cells. Although these tumour-suppressive miRNAs are potential therapeutic agents, their clinical efficacy may be limited because of their vulnerability to RNase-rich microenvironments and low in vivo transfection rates. We developed synthetic miR-214 s with enhanced cytotoxicity, RNase resistance, and quantity of miR-214 in/on cells. These synthetic miR-214 s were synthesized by various chemical modifications (such as 4'-aminoethyl-2'-fluoro, 2'-fluoro, 2'-O-methyl, phosphorothioate, and oligospermine modifications) of the wild-type mature miR-214 sequences. Transfection of HSA cells with synthetic miR-214 (miR-214 5AE) demonstrated significant growth suppressive effect and induced the strongest apoptotic response. Synthetic miR-214 s (miR-214 5AE, miR-214 10AE, and miR-214 OS) were much more stable than mature miR-214 s in foetal bovine serum. Similar to mature miR-214, 5AE and OS suppressed the expression level of COP1 in HSA cells. The quantity of synthetic miR-214 s in/on cells was higher than that of mature miR-214. In conclusion, we developed a clinically applicable, synthetic miR-214 5AE that regulates the COP1 protein expression similar to that mediated by mature miR-214. Additionally, miR-214 5AE confers better cytotoxicity, nuclease resistance, and transfection rate than mature miR-214. Thus, miR-214 5AE could potentially be a novel miRNA-based chemotherapeutic agent that could improve the prognosis of HSA. Its in vivo effects on canine HSA has need to be examined in future. This article is protected by copyright. All rights reserved.