Identification of Dormancy-Associated MicroRNAs for the Design of Osteosarcoma-Targeted Dendritic Polyglycerol Nanopolyplexes.

The presence of dormant, microscopic cancerous lesions possesses a major obstacle for the treatment of metastatic and recurrent cancers. While it is well-established that microRNAs play a major role in tumorigenesis, their involvement in tumor dormancy has yet to be fully elucidated. We established and comprehensively characterized dormant and fast-growing human osteosarcoma models. Using these pairs of mouse tumor models, we identified three novel regulators of osteosarcoma dormancy: miR-34a, miR-93 and miR-200c. This report shows that loss of these microRNAs occurs during the switch from dormant avascular into fast-growing angiogenic phenotype. We validated their downregulation in patients' tumor samples compared to normal bone making them attractive candidates for osteosarcoma therapy. Successful delivery of miRNAs is a challenge, hence, we synthesized an aminated polyglycerol dendritic nanocarrier, PG-NH2, and designed PG-NH2-microRNA polyplexes to target cancer. Reconstitution of these microRNAs using PG-NH2 polyplexes into Saos-2 and MG-63 cells, which generate fast-growing osteosarcomas, reduced the levels of their target genes, MET proto-oncogene, hypoxia-inducible factor 1α, and moesin, critical to cancer angiogenesis and cancer cells' migration. We further demonstrate that these microRNAs attenuate the angiogenic capabilities of fast-growing osteosarcoma in-vitro and in-vivo. Treatment with each of these microRNAs using PG-NH2 significantly prolonged the dormancy period of fast-growing osteosarcomas in-vivo. Taken together, these findings suggest that nanocarrier-mediated delivery of microRNAs involved in osteosarcoma tumor-host interactions can induce a dormant-like state.