TNKS1BP1 Facilitates Ubiquitination of CNOT4 by TRIM21 to Promote Hepatocellular Carcinoma Progression and Immune Evasion

Immune checkpoint inhibitors, particularly PD-1/PD-L1 blockades, have been approved for unresectable hepatocellular carcinoma (HCC). However, high resistance rates still limit their efficacy, highlighting the urgent need to understand the underlying mechanisms and develop strategies for overcoming the resistance. In this study, tankyrasel binding protein 1 (TNKS1BP1) was found to interact with tripartite motif containing 21 (TRIM21) and mediated the ubiquitination of CCR4-NOT transcription complex subunit 4 (CNOT4) at the K239 residue via K48 and K6 linkage, which was essential for its tumorigenesis function. Autophagy and lipid reprogramming were identified as two possible mechanisms underlying the pro-tumor effect of TNKS1BP1. Upregulated TNKS1BP1 inhibited autophagy while induced lipid accumulation by inhibiting the JAK2/STAT3 pathway upon the degradation of CNOT4 in HCC. Importantly, knocking down TNKS1BP1 synergized with anti-PD-L1 treatment by upregulating PD-L1 expression on tumor cells via the JAK2/STAT3 pathway, and remodeling the tumor microenvironment by increasing infiltration of tumor-infiltrating lymphocytes as well as augmenting the effect of cytotoxic T lymphocytes. In conclusion, this study identified TNKS1BP1 as a predictive biomarker for patient prognosis and a promising therapeutic target to overcome anti-PD-L1 resistance in HCC.