Ultrasound-responsive nanodroplets activate the Hippo pathway via ROS-MST1-YAP cascade for breast cancer therapy

Dysregulated Hippo signaling critically promotes malignant proliferation, invasion and distant metastasis across multiple cancers, while precise and coordinated modulation of this core pathway remains a major unmet therapeutic hurdle in clinical cancer treatment. Here, we report for the first time the albumin-based, ultrasound-responsive nanodroplets (FLU-NDs) encapsulating fluvastatin (FLU) to achieve accurate and targeted Hippo pathway reprogramming for efficient tumor suppression. FLU-NDs possess satisfactory drug-loading capability, excellent biocompatibility, and robust contrast-enhanced ultrasound performance. Notably, FLU-NDs achieve efficient tumor accumulation through a dual-delivery strategy that integrates albumin-mediated enrichment with ultrasound-triggered spatiotemporal precise release. Mechanistically, we provide evidence for the first time that ultrasound-targeted microbubble destruction (UTMD) combined with FLU-NDs enables synergistic modulation of Hippo pathway through a reactive oxygen species (ROS)-mammalian sterile 20-like kinase 1 (MST1)-yes-associated protein (YAP) regulatory axis. Specifically, cavitation-induced ROS effectively activates upstream kinase MST1, while ultrasound-triggered release of FLU suppresses the downstream YAP, thereby facilitating coordinated upstream activation and downstream inhibition. Using this previously unrecognized UTMD-associated Hippo modulation strategy, FLU-NDs induce robust apoptosis, reverse EMT, and significantly inhibit tumor growth and metastasis in vitro and in vivo. Collectively, this study establishes a novel, high-efficacy and low-toxicity theranostic platform for precise Hippo-targeted cancer therapy.