Ultrasound-Mediated Microbubble Destruction Suppresses Melanoma Tumor Growth

Melanoma is one of the most aggressive types of cancer, and its incidence has increased rapidly in the past few decades. In this study, we investigated a novel treatment approach, the use of low-intensity ultrasound (2.3 W/cm² at 1 MHz)-mediated Optison microbubble (MB) destruction (UMMD) to treat melanoma in a flank tumor model. The effect of UMMD was first evaluated in the melanoma cell line B16 F10 (B16) in vitro and then in mice inoculated with B16 cells. MB⁺B16 cells were exposed to US in vitro, resulting in significant cell death proportional to duty cycle (R² = 0.74): approximately 30%, 50%, 80% and 80% cell death at 10%, 30%, 50% and 100% DC respectively. Direct implantation of tumors with MBs, followed by sonication, resulted in retarded tumor growth and improved survival (p = 0.0106). Immunohistochemical analyses confirmed the significant changes in expression of the cell proliferation marker Ki67 (p = 0.037) and a microtubule-associated protein 2 (p = 0.048) after US + MB treatment. These results suggest that UMMD could be used as a possible treatment approach in isolated melanoma and has the potential to translate to clinical trials.