A novel USP4 inhibitor suppresses colorectal cancer stemness and enhances chemotherapy sensitivity by promoting the degradation of β-catenin and Twist1

The high mortality rate of metastasis colorectal cancer (CRC) is mainly due to chemotherapy resistance. Evidence implicates cancer stem cells (CSCs) play essential roles in chemoresistance. The deubiquitinating enzymes are vital regulators in both CSCs maintenance. Targeting deubiquitinase might be potential strategies to clear CSCs and overcome chemotherapy resistance. Here, we demonstrated that ubiquitin-specific peptidase 4 (USP4) is a key regulator of cancer stemness by stabilizing β-catenin and Twist1 proteins in CRC cells. Additionally, U4-I05, a novel natural small molecule that targets the enzyme activity of USP4 is characterized. U4-I05 binds to the catalytic domain of USP4 at nanomolar concentrations, resulting in the proteasome-mediated degradation of β-catenin and Twist1. Furthermore, U4-I05 attenuated CSC features and augmented sensitivity to oxaliplatin and 5-fluorouracil. In a genetically engineered CRC mouse model, U4-I05 inhibited tumor metastasis and prolonged survival. Overall, this study identifies U4-I05 as a USP4 inhibitor that has meaningful efficacy toward CRC.