Hepatocellular carcinoma (HCC) can have viral or non-viral causes1–5. Non-alcoholic steatohepatitis (NASH) is an important driver of HCC. Immunotherapy has been approved for treating HCC, but biomarker-based stratification of patients for optimal response to therapy is an unmet need6,7. Here we report the progressive accumulation of exhausted, unconventionally activated CD8+PD1+ T cells in NASH-affected livers. In preclinical models of NASH-induced HCC, therapeutic immunotherapy targeted at programmed death-1 (PD1) expanded activated CD8+PD1+ T cells within tumours but did not lead to tumour regression, which indicates that tumour immune surveillance was impaired. When given prophylactically, anti-PD1 treatment led to an increase in the incidence of NASH–HCC and in the number and size of tumour nodules, which correlated with increased hepatic CD8+PD1+CXCR6+, TOX+, and TNF+ T cells. The increase in HCC triggered by anti-PD1 treatment was prevented by depletion of CD8+ T cells or TNF neutralization, suggesting that CD8+ T cells help to induce NASH–HCC, rather than invigorating or executing immune surveillance. We found similar phenotypic and functional profiles in hepatic CD8+PD1+ T cells from humans with NAFLD or NASH. A meta-analysis of three randomized phase III clinical trials that tested inhibitors of PDL1 (programmed death-ligand 1) or PD1 in more than 1,600 patients with advanced HCC revealed that immune therapy did not improve survival in patients with non-viral HCC. In two additional cohorts, patients with NASH-driven HCC who received anti-PD1 or anti-PDL1 treatment showed reduced overall survival compared to patients with other aetiologies. Collectively, these data show that non-viral HCC, and particularly NASH–HCC, might be less responsive to immunotherapy, probably owing to NASH-related aberrant T cell activation causing tissue damage that leads to impaired immune surveillance. Our data provide a rationale for stratification of patients with HCC according to underlying aetiology in studies of immunotherapy as a primary or adjuvant treatment.

Obesity increases hepatocellular carcinoma (HCC) risks via unknown mediators. We report that hepatic unconventional prefoldin RPB5 interactor (URI) couples nutrient surpluses to inflammation and non-alcoholic steatohepatitis (NASH), a common cause of HCC. URI-induced DNA damage in hepatocytes triggers inflammation via T helper 17 (Th17) lymphocytes and interleukin 17A (IL-17A). This induces white adipose tissue neutrophil infiltration mediating insulin resistance (IR) and fatty acid release, stored in liver as triglycerides, causing NASH. NASH and subsequently HCC are prevented by pharmacological suppression of Th17 cell differentiation, IL-17A blocking antibodies, and genetic ablation of the IL-17A receptor in myeloid cells. Human hepatitis, fatty liver, and viral hepatitis-associated HCC exhibit increased IL-17A correlating positively with steatosis. IL-17A blockers may prevent IR, NASH, and HCC in high-risk patients.

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Molecular mechanisms responsible for hepatocellular carcinoma (HCC) remain largely unknown. Using genetically engineered mouse models, we show that hepatocyte-specific expression of unconventional prefoldin RPB5 interactor (URI) leads to a multistep process of HCC development, whereas its genetic reduction in hepatocytes protects against diethylnitrosamine (DEN)-induced HCC. URI inhibits aryl hydrocarbon (AhR)- and estrogen receptor (ER)-mediated transcription of enzymes implicated in L-tryptophan/kynurenine/nicotinamide adenine dinucleotide (NAD(+)) metabolism, thereby causing DNA damage at early stages of tumorigenesis. Restoring NAD(+) pools with nicotinamide riboside (NR) prevents DNA damage and tumor formation. Consistently, URI expression in human HCC is associated with poor survival and correlates negatively with L-tryptophan catabolism pathway. Our results suggest that boosting NAD(+) can be prophylactic or therapeutic in HCC.

The mobilization of metabolic energy from adipocytes depends on a tightly regulated balance between hydrolysis and resynthesis of triacylglycerides (TAGs). Hydrolysis is stimulated by b-adrenergic signalling to PKA that mediates phosphorylation of lipolytic enzymes, including hormonesensitive lipase (HSL). TAG resynthesis is associated with high-energy consumption, which when inordinate, leads to increased AMPK activity that acts to restrain hydrolysis of TAGs by inhibiting PKA-mediated activation of HSL. Here, we report that in primary mouse adipocytes, PKA associates with and phosphorylates AMPKa1 at Ser-173 to impede threonine (Thr-172) phosphorylation and thus activation of AMPKa1 by LKB1 in response to lipolytic signals. Activation of AMPKa1 by LKB1 is also blocked by PKA-mediated phosphorylation of AMPKa1 in vitro. Functional analysis of an AMPKa1 species carrying a non-phosphorylatable mutation at Ser-173 revealed a critical function of this phosphorylation for efficient release of free fatty acids and glycerol in response to PKAactivating signals. These results suggest a new mechanism of negative regulation of AMPK activity by PKA that is important for converting a lipolytic signal into an effective lipolytic response.

Interleukin-17A (IL-17A) is a major mediator of tissue inflammation in many autoimmune diseases. Anti-IL-17A is an effective treatment for psoriasis and is showing promise in clinical trials in multiple sclerosis. In this study, we find that IL-17A-defective mice or mice treated with anti-IL-17A at induction of experimental autoimmune encephalomyelitis (EAE) are resistant to disease and have defective priming of IL-17-secreting gd T (gdT17) cells and Th17 cells. However, T cells from Il17a À/À mice induce EAE in wild-type mice following in vitro culture with autoantigen, IL-1b, and IL-23. Furthermore, treatment with IL-1b or IL-17A at induction of EAE restores disease in Il17a À/À mice. Importantly, mobilization of IL-1b-producing neutrophils and inflammatory monocytes and activation of gdT17 cells is reduced in Il17a À/À mice. Our findings demonstrate that a key function of IL-17A in central nervous system (CNS) autoimmunity is to recruit IL-1b-secreting myeloid cells that prime pathogenic gdT17 and Th17 cells.

S6 kinase 1 (S6K1) acts to integrate nutrient and growth factor signals to promote cell growth but also cell survival as a mitochondria-tethered protein kinase that phosphorylates and inactivates the proapoptotic molecule BAD. Here we report that the prefoldin chaperone URI represents a mitochondrial substrate of S6K1. In growth factor-deprived or rapamycin-treated cells, URI forms stable complexes with protein phosphatase (PP)1gamma at mitochondria, thereby inhibiting the activity of the bound enzyme. Growth factor stimulation induces disassembly of URI/PP1gamma complexes through S6K1-mediated phosphorylation of URI at serine 371. This activates a PP1gamma-dependent negative feedback program that decreases S6K1 activity and BAD phosphorylation, thereby altering the threshold for apoptosis. These findings establish URI and PP1gamma as integral components of an S6K1-regulated mitochondrial pathway dedicated, in part, to oppose sustained S6K1 survival signaling and to ensure that the mitochondrial threshold for apoptosis is set in accord with nutrient and growth factor availability.

SummaryHepatocellular carcinoma (HCC) is an aggressive primary liver cancer. However, its origin remains a debated question. Using human data and various hepatocarcinogenesis mouse models, we show that, in early stages, transformed hepatocytes, independent of their proliferation status, activate hepatic progenitor cell (HPC) expansion. Genetic lineage tracing of HPCs and hepatocytes reveals that, in all models, HCC originates from hepatocytes. However, whereas in various models tumors do not emanate from HPCs, tracking of progenitors in a model mimicking human hepatocarcinogenesis indicates that HPCs can generate benign lesions (regenerative nodules and adenomas) and aggressive HCCs. Mechanistically, galectin-3 and α-ketoglutarate paracrine signals emanating from oncogene-expressing hepatocytes instruct HPCs toward HCCs. α-Ketoglutarate preserves an HPC undifferentiated state, and galectin-3 maintains HPC stemness, expansion, and aggressiveness. Pharmacological or genetic blockage of galectin-3 reduces HCC, and its expression in human HCC correlates with poor survival. Our findings may have clinical implications for liver regeneration and HCC therapy.