Advillin stabilizes YAP to sustain oncogenic transcription and creates therapeutic vulnerability in rhabdomyosarcoma

Background Rhabdomyosarcoma (RMS) is the most common pediatric soft-tissue sarcoma. Despite intensive multimodal therapy, outcomes remain poor for patients with metastatic or recurrent disease, underscoring an urgent need for novel molecularly targeted therapies. We previously identified advillin (AVIL), a gelsolin family actin-binding protein, as a novel oncogenic driver overexpressed in RMS and associated with poor clinical outcomes. However, the downstream molecular mechanisms by which AVIL drives and sustains oncogenic signaling in RMS have remained unclear. Here, we investigated AVIL-dependent regulation of the Hippo pathway effector Yes-associated protein (YAP) and the therapeutic relevance of the AVIL–YAP axis in RMS. Methods AVIL expression was evaluated in clinical RMS specimens across histologic subtypes, tumor grades, and clinical stages. Transcriptomic, molecular, and functional analyses investigated AVIL-dependent YAP regulation in RMS cells, mesenchymal stem cells, and patient-derived models. Therapeutic dependency on the AVIL–YAP signaling axis was assessed using genetic and pharmacologic approaches in vitro and in patient-derived xenograft models. Statistical analyses included unpaired two-tailed t-tests, one-way ANOVA, log-rank (Mantel–Cox) tests, and REML-based mixed-effects models. Nonlinear regression determined IC₅₀ values. Results AVIL was broadly expressed across RMS specimens spanning stages, grades, and subtypes, and functioned as an upstream regulator of the Hippo effector YAP. AVIL promoted YAP stabilization and nuclear accumulation, enhancing YAP-dependent transcription alongside altered Hippo pathway regulation. Genetic AVIL depletion impaired YAP signaling and RMS cell survival, while promoting myogenic differentiation. Actin perturbation diminished AVIL-associated nuclear YAP, and mutations affecting AVIL actin-regulatory functions attenuated YAP activity and suppressed proliferation and migration, supporting a role for actin remodeling in AVIL-driven tumorigenesis. AVIL-high RMS models showed heightened sensitivity to YAP inhibition in vitro, whereas AVIL -depleted cells showed diminished responsiveness. Pharmacologic YAP inhibition suppressed YAP-dependent transcription in vitro and reduced tumor incidence in AVIL-high RMS xenografts in vivo . Conclusions Our findings identify a previously unrecognized AVIL–YAP axis that sustains oncogenic transcription and tumorigenic phenotypes in RMS. These results establish AVIL-mediated YAP dependency as a therapeutically actionable vulnerability and support targeting this pathway as a treatment strategy for aggressive RMS.