The Extracellular Matrix Regulates Invasion in Fusion-Negative Rhabdomyosarcoma via YAP-PIEZO1 Signaling Axis.

Background: Fusion-negative rhabdomyosarcoma (FNRMS) represents the most prevalent subtype of rhabdomyosarcoma, the most common pediatric soft-tissue sarcoma. Although its invasion is a leading cause of recurrence and poor prognosis, its underlying mechanism remains unclear. We investigated how extracellular matrix density regulates FNRMS progression via mechano-transduction. Methods: We used three-dimensional spheroid invasion assays with FNRMS cells embedded in varying collagen concentrations. Mechanistic insights were gained through immunofluorescence, sequencing reanalysis, calcium live-cell imaging, and pharmacological inhibition of the YAP-PIEZO1 axis. Results: High extracellular matrix density significantly enhanced invasive spreading, correlating with increased YAP nuclear localization. YAP overexpression was sufficient to promote invasive spreading, while its inhibition attenuated the matrix-enhanced phenotype. We identified PIEZO1 as a direct transcriptional target of YAP. High extracellular matrix density stimulated PIEZO1-dependent calcium influx, which was required for invasion. Furthermore, elevated PIEZO1 expression was significantly associated with poorer overall survival in FNRMS patients. Targeting YAP effectively suppressed both calcium flux and invasion. Conclusions: Our findings establish a YAP-PIEZO1 axis linking extracellular matrix density to FNRMS invasion. This mechanosensitive pathway represents a potential therapeutic vulnerability in aggressive FNRMS.