USP9X is a mechanosensitive deubiquitinase that controls tumor cell invasiveness and drug response through YAP stabilization

Ubiquitin removal by deubiquitinases (DUBs) is crucial for protein activity and homeostasis. While tumor cells adapt to treatment and environmental stress, the role of DUBs in sensing mechanical signals from the extracellular matrix (ECM) remains an unexplored area. Using melanoma cells cultured on collagen matrices of varying stiffness and activity-based ubiquitin probe profiling combined with quantitative proteomics, we identify ubiquitin specific peptidase 9 X-linked (USP9X) as a stiffness-sensitive DUB acting through the discoidin domain receptor (DDR)/actomyosin signaling pathway. USP9X regulates levels of the mechanosensor YAP by preventing its proteasomal degradation via deubiquitination. Inhibition or knockdown of USP9X reduced YAP expression, impaired tumor cell migration, invasion, and ECM contraction, and decreased metastatic potential in vivo. Targeting USP9X also enhanced the effectiveness of BRAF-targeted therapies by limiting YAP-mediated mechanosensing, drug resistance, and tumor relapse. These findings establish USP9X as a mechanoresponsive DUB essential for cancer cell adaptation to mechanical cues, proposing it as a targetable mechanosensitive therapeutic target in cancer.