# Activated ATF6α is a hepatic tumour driver restricting immunosurveillance

## TL;DR

This study shows that prolonged activation of ATF6α in liver cancer drives tumor growth and suppresses immune responses, making it a potential target for treatment.

## Contribution

The study reveals ATF6α as a novel tumor driver and immunosuppressor in hepatocellular carcinoma, linking it to metabolic changes and immune evasion.

## Key findings

- Activated ATF6α correlates with aggressive tumor traits and reduced survival in human HCC.
- ATF6α induces ER stress, glycolysis, and immunosuppression in liver cancer models.
- Targeting ATF6α reduces HCC progression and improves response to immunotherapy.

## Abstract

Hepatocellular carcinoma (HCC) is the fastest growing cause of cancer-related mortality and there are limited therapies1. Although endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are implicated in HCC, the involvement of the UPR transducer ATF6α remains unclear2. Here we demonstrate the function of ATF6α as an ER-stress-inducing tumour driver and metabolic master regulator restricting cancer immunosurveillance for HCC, in contrast to its well-characterized role as an adaptive response to ER stress3. ATF6α activation in human HCC is significantly correlated with an aggressive tumour phenotype, characterized by reduced patient survival, enhanced tumour progression and local immunosuppression. Hepatocyte-specific ATF6α activation in mice induced progressive hepatitis with ER stress, immunosuppression and hepatocyte proliferation. Concomitantly, activated ATF6α increased glycolysis and directly repressed the gluconeogenic enzyme FBP1 by binding to gene regulatory elements. Restoring FBP1 expression limited ATF6α-activation-related pathologies. Prolonged ATF6α activation in hepatocytes triggered hepatocarcinogenesis, intratumoural T cell infiltration and nutrient-deprived immune exhaustion. Immune checkpoint blockade (ICB)4 restored immunosurveillance and reduced HCC. Consistently, patients with HCC who achieved a complete response to immunotherapy displayed significantly increased ATF6α activation compared with those with a weaker response. Targeting Atf6 through germline ablation, hepatocyte-specific ablation or therapeutic hepatocyte delivery of antisense oligonucleotides dampened HCC in preclinical liver cancer models. Thus, prolonged ATF6α activation drives ER stress, leading to glycolysis-dependent immunosuppression in liver cancer and sensitizing to ICB. Our findings suggest that persistently activated ATF6α is a tumour driver, a potential stratification marker for ICB response and a therapeutic target for HCC.

ATF6α activation in human and preclinical models of hepatocellular carcinoma is significantly associated with an aggressive tumour phenotype characterized by reduced survival, glycolytic reprogramming and local immunosuppression.