Local Delivery of miR-27a* Using Ultrasound-Targeted Microbubble Cavitation Inhibits Squamous Cell Carcinoma Growth

Ultrasound-targeted microbubble (MB) cavitation (UTMC) is an image-guided therapeutic oligonucleotide delivery platform utilizing intravenously injected gas-filled ultrasound contrast agents, which carry the therapeutic on the MB shell. During transit of MBs in the microcirculation of target tissue, ultrasound causes MB oscillation, facilitating endocytosis-independent payload uptake within insonified cells. Here, we tested the hypothesis that UTMC-mediated miR-27a* delivery will reduce tumor growth rate and result in accumulation of miR-27a* within tumor cells and the tumor microenvironment.

We used UTMC to deliver miR-27a* to SCC-VII cells in vitro and in SCC-VII mouse tumor models. Pulsed ultrasound was delivered during intravenous (i.v.) infusion of lipid encapsulated MBs loading either miR-27a* (miR-27a*-MB + UTMC) or negative control MBs (Con-miR-MB + UTMC).

miR-27a*-MB+UTMC treatment significantly reduced SCC-VII cell viability in vitro and SCC-VII tumor growth in vivo compared to negative controls (Con-miR-MB+UTMC, i.v. miR-27a* or no treatment). Forty-eight hours following treatment, protein expression of direct miR-27a* targets (epidermal growth factor receptor [EGFR], NUP62 and ΔNP63α) was significantly reduced in miR-27a*-MB + UTMC vs i.v. miR-27a* or Con-miR-MB + UTMC. Further, whereas i.v. miR-27a* did not decrease tumor expression of these proteins vs. non-treated tumors, miR-27a*-MB + UTMC significantly reduced tumor expression of EGFR, NUP62 and ΔNP63α by 50%-75%, compared to non-treated tumors.

These data substantiate the utility of UTMC for non-invasive delivery of oligonucleotide payloads to extravascular target sites and suggests the therapeutic potential of miR-27a* for the treatment of head and neck squamous cell carcinoma.