TRIM21 as a Context-Dependent Regulator in Hepatocellular Carcinoma: Integrating Etiological Landscapes (HBV/NASH) with Core Tumor Progression Mechanisms.

Tripartite motif-containing protein 21 (TRIM21), an E3 ubiquitin ligase of the TRIM superfamily, modulates critical cellular processes including ubiquitination, autophagy, and oxidative stress response. Accumulating evidence highlights its context-dependent regulatory roles in hepatocellular carcinoma (HCC)-the most prevalent primary liver malignancy with high mortality and limited therapeutic efficacy. This review systematically summarizes the core mechanisms by which TRIM21 orchestrates HCC progression: ① Autophagy regulation: TRIM21 modulates HCC autophagy via multiple axes, including CCR4-NOT complex (TNKS1BP1/CNOT4)-mediated substrate ubiquitination, ATG14-dependent autophagosome initiation, and RETREG1-driven reticulophagy, with context-dependent effects on tumor proliferation. ② Drug resistance: TRIM21 enhances oxaliplatin sensitivity by ubiquitinating and degrading G6PD (the rate-limiting enzyme of the pentose phosphate pathway), while its role in sorafenib resistance involves dual pathways-the MST1/YAP axis and the ApoE/cholesterol/PI3K-AKT cascade. ③ Metastasis suppression: TRIM21 restricts HCC invasion and metastasis by ubiquitinating key oncoproteins, preserving epithelial integrity and inhibiting mesenchymal transition. ④ Reactive oxygen species (ROS) balance: TRIM21 regulates oxidative stress in HCC via the SQSTM1/p62-Keap1-NRF2 axis, coordinating with HIF1α to modulate antioxidant responses and tumor cell survival. Additionally, we discuss the regulatory significance of TRIM21 in HCC associated with hepatitis B virus (HBV) infection (via HBx/DNA polymerase ubiquitination) and nonalcoholic steatohepatitis (NASH) (via suppressing lipogenic enzymes to reduce steatosis-driven carcinogenesis). This review provides a theoretical basis for TRIM21 as a potential diagnostic marker and therapeutic target for HCC.