In Vitro Biophysical and Biological Characterization of Lipid Nanoparticles Co-Encapsulating Oncosuppressors miR-199b-5p and miR-204-5p as Potentiators of Target Therapy in Metastatic Melanoma.

Uncontrolled MAPK signaling is the main oncogenic driver in metastatic melanomas bearing mutations in BRAF kinase. These tumors are currently treated with the combination of BRAF/MEK inhibitors (MAPKi), but this therapy is plagued by drug resistance. In this context we recently discovered that several microRNAs are involved in the development of drug resistance. In particular miR-204-5p and miR-199b-5p were found to function as antagonists of resistance because their enforced overexpression is able to inhibit melanoma cell growth in vitro either alone or in combination with MAPKi. However, the use of miRNAs in therapy is hampered by their rapid degradation in serum and biological fluids, as well as by the poor intracellular uptake. Here, we developed lipid nanoparticles (LNPs) encapsulating miR-204-5p, miR-199b-5p individually or in combination. We obtained LNPs with mean diameters < 200 nm and high miRNA encapsulation efficiency. These formulations were tested in vitro on several melanoma cell lines sensitive to MAPKi or rendered drug resistant. Our results show that LNPs encapsulating combinations of the two oncosuppressor miRNAs are highly efficient in impairing melanoma cell proliferation and viability, affect key signaling pathways involved in melanoma cell survival, and potentiate the efficacy of drugs inhibiting BRAF and MEK. These results warrant further assessment of the anti-tumor efficacy of oncosuppressor miRNAs encapsulating LNPs in in vivo tumor models.