Sonodynamic therapy using 5-aminolevulinic acid enhances the efficacy of bleomycin

• Efficacy of sonodynamic therapy (SDT) with bleomycin was studied in EMT-6 cells.
• SDT with bleomycin was more cytotoxic than SDT alone.
• In vivo, SDT with bleomycin achieved greater tumor growth inhibition than SDT alone.
• Bleomycin improved the efficacy of SDT.
• SDT with bleomycin might be a noninvasive treatment for deep-seated tumors.

Sonodynamic therapy (SDT) kills tumor cells through the synergistic effects of ultrasound and a sonosensitizer agent. We examined whether 5-aminolevulinic acid (5-ALA)-based SDT at 1 or 3 MHz could enhance the cytotoxicity of bleomycin (BLM) toward mouse mammary tumor cells both in vitro and in vivo. At 1 MHz, cell viability in the 5-ALA-based SDT group at 1, 2, and 3 W/cm2 was 34.30%, 50.90%, and 60.16%, respectively. Cell viability in the 5-ALA-based SDT + BLM group at 1, 2, and 3 W/cm2 was 0.09%, 0.32%, and 0.17%, respectively. In contrast, at 3 MHz, 5-ALA-based SDT + BLM did not show pronounced cytotoxicity. In the in vivo study, 5-ALA-based SDT + BLM was significantly more cytotoxic than 5-ALA-based SDT at 1 MHz and 3 MHz. These findings suggest that the mechanism of tumor shrinkage induced by 5-ALA-based SDT + BLM might involve not only direct cell killing, but also vascular shutdown. Thus, we show here that 5-ALA-based SDT enhances the efficacy of BLM both in vitro and in vivo.