IKKβ and USP28 Regulate HEY1 Stability to Promote Cancer Stemness and Immune Evasion in Hepatocellular Carcinoma

ABSTRACT Hepatocellular carcinoma (HCC), the most prevalent form of primary liver cancer, is driven by cancer stem cells (CSCs) and an immunosuppressive tumor microenvironment, which may underlie the limited efficacy of immune checkpoint blockade therapy. Here, we report that HEY1 plays a crucial role in sustaining HCC stemness and undergoes polyubiquitylation during liver CSC differentiation. Mechanistically, USP28 interacts with HEY1 and deubiquitinates its lysine 87 residue, thereby stabilizing HEY1 and enhancing the stem‐like properties of liver cancer cells. Moreover, IKKβ phosphorylates HEY1 at serine 40, facilitating its interaction with USP28. Loss of USP28 reduces PD‐L1 expression, increases effector cytokine production, and suppresses tumor growth in mice. Notably, combining a USP28 inhibitor with anti‐PD‐1 immunotherapy results in enhanced tumor regression and significantly prolonged overall survival in mouse tumor models. Collectively, these findings identify USP28 as a potential biomarker for stratifying patients likely to benefit from anti‐PD‐1/PD‐L1 therapies in HCC. Furthermore, we uncover a previously unrecognized IKKβ‐USP28‐HEY1 signaling axis that governs HEY1 stability and cancer stemness, offering new opportunities for synergistic therapeutic strategies in HCC.