WNK4 Enhances Anti-PD-1 Resistance and Promotes Tumor Progression in Hepatocellular Carcinoma by Reprogramming Cysteine Metabolism in Cancer-Associated Fibroblasts.

Hepatocellular carcinoma (HCC) is the most prevalent subtype of primary liver cancer. Immunotherapy, particularly targeting immune checkpoints such as programmed cell death protein 1 (PD-1), has shown considerable therapeutic promise. Bioinformatic analysis of Gene Expression Omnibus datasets demonstrated significant upregulation of WNK lysine deficient protein kinase 4 (WNK4) expression in HCC tissues obtained from untreated patients or anti-PD-1 non-responders, suggesting a potential role for WNK4 in HCC progression and immunotherapy resistance. Through a series of experiments, we confirmed that WNK4 promoted the proliferative and migrative abilities of HCC cells and enhanced the resistance of HCC model mice to anti-PD-1 therapy. The tumor microenvironment, particularly cancer-associated fibroblasts (CAFs), critically influences immunotherapy efficacy. The current study uncovered that WNK4 was transferred by HCC cell-derived exosomes into CAFs and promoted the cysteine metabolic reprogramming. Moreover, WNK4-mediated promotional effects of CAFs on the malignant phenotypes of HCC cells and anti-PD-1 resistance were in a cysteine-dependent manner. According to mechanism investigation, WNK4 could bind high mobility group box 1 (HMGB1) and induce its phosphorylation and cytoplasmic retention, thus reducing nuclear HMGB1-p53 interaction to enhance cystathionine gamma-lyase (CTH) expression. In summary, this study unveils a novel WNK4-HMGB1-p53 axis in CAFs that promotes HCC progression and modulates cysteine metabolism to foster immunotherapy resistance, offering potential therapeutic targets for HCC.