USP33 contributes to EMT and Lenvatinib resistance by enhancing eEF1A1-mediated ILEI protein synthesis in hepatocellular carcinoma.

Lenvatinib resistance represents a primary cause of treatment failure in patients with advanced hepatocellular carcinoma (HCC), while its underlying molecular mechanisms remain incompletely understood. Using a CRISPR knockout library targeting human ubiquitination-related proteins, we identified ubiquitin-specific protease 33 (USP33) as a key factor of lenvatinib resistance in HCC. Transcriptome sequencing further demonstrated that USP33 induces epithelial-mesenchymal transition (EMT), and its downregulation suppresses EMT and enhances lenvatinib sensitivity in HCC cells. Through proteomic analysis, we identified interleukin-like EMT-inducing factor (ILEI) as a downstream target regulated by USP33 in this process. Mechanistically, USP33 functions as a deubiquitinase for eukaryotic translation elongation factor 1alpha 1 (eEF1A1), inhibiting its ubiquitin-mediated degradation and enhancing its protein stability, thereby promoting ILEI protein synthesis. Together, these findings reveal the significant role of the USP33/eEF1A1/ILEI axis in contributing to EMT and lenvatinib resistance, offering potential therapeutic targets and a rationale for strategies to overcome lenvatinib resistance in HCC.