Identification of DDX5 as a Potential Therapeutic Target of Osteosarcoma Using Thiazolone Probes

Osteosarcoma (OS) is a rare malignant tumor that has predominantly affected children and adolescents in the past 50 years. The genomes of OS tumors exhibit a high degree of complexity, which leads to the great challenge of target identification for anti-OS. To date, no efficient therapeutic target for the treatment of OS has been validated in clinical practice. In our previous drug hunting for the treatment of OS by phenotypic screening, we found that thiazolone derivate (R)-8i was an effective and selective inhibitor against OS in MNNG/HOS cells and in vivo. However, the mechanism of action and specific molecular targets of (R)-8i remain unclear. In this study, we design and synthesize the photo-cross-linking probes based on the lead compound (R)-8i and identify DDX5 as a potential target protein using an activity-based protein profiling strategy. Further experiments including Western blot, shRNA knockdown experiments, cell colony formation, wound healing assays, and cellular thermal shift assays support that (R)-8i binds to DDX5 and induces its degradation, which affect cell proliferation and migration through the PI3K-AKT-mTOR signaling pathway. The research shows that DDX5 is a potential therapeutic target for the treatment of OS.