Exploring the potential of engineered exosomes as delivery systems for tumor-suppressor microRNA replacement therapy in ovarian cancer

概要

〔目　的(Purpose)〕
Ovarian cancer is one of the malignant tumors that seriously threatens women’s health worldwide. Considering pivotal roles of microRNA (miRNA) in ovarian cancer biology, tumor suppressor (TS) miRNA is an attractive target; however, clinical trials have failed due to the difficulties of miRNA delivery, and therefore the development of a novel drug delivery system (DDS) is warranted, Exosomes, which are small extracellular vesicles (30-150 nm) derived from a multivesicular body, are stable in circulation and selectively picked up by cancer cells, indicating they can serve as a miRNA carrier. The aim of this study is to pursue the possibi1ity of exosomes as a carrier for miRNA replacement therapy for ovarian cancer (OC).

〔方法ならびに成績(Methods/Resu Its)〕　
First, exosomes were purified from primary-cultured omental fibroblasts from ovarian cancer patients mainly by iodixanol (OptiPrepTM) density gradient ultracentrifugation. miR-199a-3p was selected as TS miRNA and synthesized miR-199a-3p tagged with Alexa-488 was loaded to exosomes by electroporation. Treatment with 199a-3p-loaded-exosomes (M199-exosomes) drastically increased miR-199a-3p expression level in OC cell1ines (CaOV3: 8592-, SKOV3; 67188-, and OVCAR3: 2280-fold). M199-exosomes suppressed c-Met expression, a direct target of miR-199a~3p, and thereby inhibited cell proliferation and invasion of OC cel11ines. In a xenograft study, M199-exosomes showed higher retention than bare miR-199a-3p in the circulation, suggesting its stability. After intraperitoneal treatment, only inoculated tumors displayed DIR fluorescence, indicating its specificity to cancer. Accordingly. M199-exosomes drastically inhibited peritoneal dissemination in mice. Immunohistochemical analyses revealed diminished c-Met expression in cancer followed by the inhibition of ERK phosphorylation and MMP2 expression.

〔総　括(Conclusion)〕
　In this study, we revealed as follows; 1. exosomes derived from fibroblasts can be successfully collected from omentum of ovarian cancer patients. 2. TS miRNA, miR-199a-3p, was successfully incorporated into exosomes, and exosomes encapsulating miR-199a-3p drastically inhibited peritoneal dissemination of ovarian cancer model mice, suggesting its therapeutic potential. Given that most ovarian cancer patients undergo omentectomy and thereby exosomes from omental fibroblasts can be obtained from those, engineered exosomes can be utilized as a drug delivery carrier for a future molecular-targeted therapies for ovarian cancer, which may lead to personalized medicine in the near future.