The paper reports the results of nanotherapy of ovarian, breast, and pancreatic cancerous
tumors by paclitaxel-loaded nanoemulsions that convert into microbubbles locally in
tumor tissue under the action of tumor-directed therapeutic ultrasound. Tumor accumulation
of nanoemulsions was confirmed by ultrasound imaging. Dramatic regression of ovarian,
breast, and orthotopic pancreatic tumors was observed in tumor therapy through systemic
injections of drug-loaded nanoemulsions combined with therapeutic ultrasound, signifying
efficient ultrasound-triggered drug release from tumor-accumulated nanodroplets. The
mechanism of drug release in the process of droplet-to-bubble conversion is discussed.
No therapeutic effect from the nanodroplet/ultrasound combination was observed without
the drug, indicating that therapeutic effect was caused by the ultrasound-enhanced
chemotherapeutic action of the tumor-targeted drug, rather than the mechanical or
thermal action of ultrasound itself. Tumor recurrence was observed after the completion
of the first treatment round; a second treatment round with the same regimen proved
less effective, suggesting that drug-resistant cells were either developed or selected
during the first treatment round.