Targeting SPAK suppresses progression and averts an immune exhaustive microenvironment in hepatocellular carcinoma.

Protein kinases contribute to hepatocellular carcinoma (HCC) development and immune evasion, posing major challenges for HCC management. Here we show STE20/SPS1-related proline/alanine-rich kinase (SPAK) as a candidate immune exhaustion-associated gene identified through a pooled screen of protein kinases. By integrating bioinformatic analyses, data from patient cohorts, and functional studies in mouse models and cell lines, we demonstrate that elevated expression of SPAK promotes HCC progression, enhances stemness, drives immune exhaustion, and contributes to resistance to targeted therapies. Mechanistically, SPAK phosphorylates GSK3β at Ser9, thereby inhibiting proteasome-mediated degradation of c-Jun and PD-L1. Additionally, we find that DNMT3B-dependent intragenic methylation of SPAK contributes to its high expression in HCC. Notably, the SPAK inhibitor exhibits potent inhibitory effects and synergizes with PD-1 blockade to enhance antitumor efficacy. In summary, these findings establish SPAK as a driver of oncogenesis and immune exhaustion in HCC and highlight dual inhibition as a potential therapeutic strategy.