Development of a miR-92a delivery system for anti-angiogenesis-based cancer therapy

RNA interference has received much attention as a novel therapeutic strategy. MicroRNA (miRNA) appears to be promising as a novel nucleic-acid medicine because it is able to suppress a series of protein expression that relates to a specific event such as angiogenesis. In the present study, we used dicetyl phosphate-tetraethylenepentamine-based polycation liposomes (TEPA-PCL) as a delivery system for miR-92a, one of the miRNAs regulating angiogenesis, and attempted to deliver miR-92a to angiogenic endothelial cells for the development of cancer therapy by anti-angiogenesis.

Cholesterol-grafted miR-92a (miR-92a-C) was bound to TEPA-PCL, and the ratio of nitrogen of TEPA-PCL to phosphorus of miR-92a-C (N/P ratio) was optimized. This complex was transfected into human umbilical vein endothelial cells (HUVECs), and the intracellular localization of miR-92a-C was observed under a confocal laser-scanning microscope by the use of fluorescein isothiocyanate-labeled miR-92a-C. After transfection of HUVECs with miR-92a-C/TEPA-PCL, the expression of miR-92a-target proteins (e.g. integrin α5, mitogen-activated protein kinase kinase 4, sphingosine-1-phosphate receptor 1) was examined by western blotting, and a tube formation assay was performed.

The complex of miR-92a-C with TEPA-PCL was formed and miR-92a-C remained stable with TEPA-PCL at the N/P ratio of 10. After transfection of HUVECs with miR-92a-C complex, miR-92a-C spread into the whole cytoplasm of the cells without any change of cellular morphology, and the expression of several proteins encoded by miR-92a-target genes was suppressed. Furthermore, the capability of forming capillary tubes was impaired in complex-treated HUVECs.

We have developed a miR-92a delivery system into angiogenic endothelial cells by the use of TEPA-PCL. These results suggest that miR-92a-C/TEPA-PCL is promising for the treatment of tumors via the suppression of angiogenesis.