Pharmacological inhibition of the <scp>PERK</scp> pathway modulates hepatocellular carcinoma growth and immune signaling

The unfolded protein response (UPR) plays an important role in tumor progression and cellular stress adaptation. In hepatocellular carcinoma (HCC), pharmacological inhibition of the protein kinase R-like endoplasmic reticulum kinase (PERK) is a potential therapeutic strategy, yet its effects on tumor growth and the microenvironment remain unclear. We investigated the selective PERK inhibitor AMG PERK 44 in a diethylnitrosamine (DEN)-induced mouse model of advanced HCC. Tumor burden, proliferation, fibrosis, immune-related gene expression, and ER stress signaling were assessed alongside analyses of single-cell RNA-sequencing data from HCC mouse models and liver-specific PERK knockout mice. Our results show that AMG PERK 44 did not alter tumor number nor cause a decrease in tumor area and proliferation. Furthermore, fibrotic burden was unchanged, although fibrosis architecture and stromal gene expression (TGF-β, CTGF, F4/80) were modified. Despite PERK inhibition, the expression of ER stress associated genes (CHOP, EIF2AK3, ERdj4) increased. Single-cell analysis revealed context-dependent PERK activity, highest in dendritic cells and macrophages under inflammatory and tumor conditions, while PERK knockout livers showed impaired UPR responses after tunicamycin treatment. Finally, AMG PERK 44 did not enhance idarubicin efficacy and caused no major off-target effects. These findings highlight the context-dependent role of PERK in the HCC microenvironment and its implications for targeting UPR pathways in liver cancer. Impact statement This study provides an evaluation of PERK as a therapeutic target in hepatocellular carcinoma by demonstrating that its inhibition does not produce the anticipated anti-tumor effects in advanced disease, but instead exerts nuanced, context-dependent influences on the tumor microenvironment.