Mechanism of NUMBL enhancing axitinib resistance in clear cell renal cell carcinoma by UCHL1-mediated deubiquitination of MMP9.

The 5-year survival rate for metastatic clear cell renal cell carcinoma (ccRCC) is only 8%. Although antiangiogenic therapy like axitinib is the first-line treatment, tumors often develop resistance rapidly. This study investigates the role of NUMB-like endocytic adaptor protein (NUMBL) in this resistance. We found that NUMBL expression is upregulated in axitinib-resistant ccRCC cells. Knocking down NUMBL in a resistant 769P cell line significantly reduced the axitinib IC(50) from 218.3 μM to 113.2 μM, thereby restoring drug sensitivity. Mechanistically, NUMBL upregulates ubiquitin C-terminal hydrolase L1 (UCHL1). UCHL1 then interacts with and deubiquitinates matrix metalloproteinase 9 (MMP9), leading to MMP9 protein stabilization and increased expression. This cascade ultimately promotes vasculogenic mimicry (VM), a nonangiogenic vascularization process that contributes to axitinib resistance. Our research elucidates this novel NUMBL/UCHL1/MMP9 axis in driving VM-mediated resistance at molecular, cellular, tissue, and animal levels. By integrating the roles of NUMBL, VM, and deubiquitination, this work establishes a theoretical foundation for understanding axitinib resistance and provides new perspectives for improving ccRCC treatment efficacy.