In an analysis of HCC samples from 956 patients, we found almost 25% to express markers of an inflammatory response. We identified 2 subclasses, characterized by adaptive or exhausted immune responses. These findings indicate that some HCCs might be susceptible to therapeutic agents designed to block the regulatory pathways in T cells, such as programmed death-ligand 1, programmed cell death 1, or transforming growth factor beta 1 inhibitors.

SUMMARY Defective Hippo/YAP signaling in the liver results in tissue overgrowth and development of hepatocellular carcinoma (HCC). Here, we uncover mechanisms of YAP-mediated hepatocyte reprogramming and HCC pathogenesis. YAP functions as a rheostat maintaining metabolic specialization, differentiation and quiescence within the hepatocyte compartment. Increased or decreased YAP activity reprograms subsets of hepatocytes to different fates associated with deregulation of the HNF4A, CTNNB1, and E2F transcriptional programs controlling hepatocyte quiescence and differentiation. Importantly, treatment with siRNA-lipid nanoparticles (siRNA-LNPs) targeting YAP restores hepatocyte differentiation and causes pronounced tumor regression in a genetically engineered mouse HCC model. Furthermore, YAP targets are enriched in an aggressive human HCC subtype characterized by a proliferative signature and absence of CTNNB1 mutations. Thus, our work reveals Hippo signaling as a key regulator of positional identity of hepatocytes, supports targeting YAP using siRNA-LNPs as a paradigm of differentiation-based therapy, and identifies an HCC subtype potentially responsive to this approach.

Background & Aims: Endothelial dysfunction plays an essential role in liver injury, yet the phenotypic regulation of liver sinusoidal endothelial cells (LSECs) remains unknown. Autophagy is an endogenous protective system whose loss could undermine LSEC integrity and phenotype. The aim of our study was to investigate the role of autophagy in the regulation of endothelial dysfunction and the impact of its manipulation during liver injury. Methods: We analyzed primary isolated LSECs from Atg7control and Atg7endo mice as well as rats after CCl4 induced liver injury. Liver tissue and primary isolated stellate cells were used to analyze liver fibrosis. Autophagy flux, microvascular function, nitric oxide bioavailability, cellular superoxide content and the antioxidant response were evaluated in endothelial cells. Results: Autophagy maintains LSEC homeostasis and is rapidly upregulated during capillarization in vitro and in vivo. Pharma-cological and genetic downregulation of endothelial autophagy increases oxidative stress in vitro. During liver injury in vivo, the selective loss of endothelial autophagy leads to cellular dysfunction and reduced intrahepatic nitric oxide. The loss of autophagy also impairs LSECs ability to handle oxidative stress and aggravates fibrosis. Conclusions: Autophagy contributes to maintaining endothelial phenotype and protecting LSECs from oxidative stress during early phases of liver disease. Selectively potentiating autophagy in LSECs during early stages of liver disease may be an attractive approach to modify the disease course and prevent fibrosis progression. Lay summary: Liver endothelial cells are the first liver cell type affected after any kind of liver injury. The loss of their unique phenotype during injury amplifies liver damage by orchestrating the response of the liver microenvironment. Autophagy is a mechanism involved in the regulation of this initial response and its manipulation can modify the progression of liver damage.

Molecular analysis of mixed hepatocellular cholangiocarcinoma (HCC-CCA) showed that cholangiolocellular carcinoma (CLC) is distinct and biliary in origin. It has none of the traits of hepatocellular carcinoma (HCC). However, within mixed HCC-CCA, stem-cell type tumors shared an aggressive nature and poor outcome, whereas the classic type showed a common cell lineage for both the HCC and the intrahepatic CCA component. The pathological classification of mixed HCC-CCA should be redefined because of the new molecular data provided.

Trunk alterations arise at early stages of cancer and are shared among all malignant cells of the tumor. In order to identify trunk alterations in HCC, we characterized early stages of hepatocarcinogenesis represented by dysplastic nodules and small lesions. Mutations in TERT, TP53 and CTNNB1 genes were the most frequent. Analyses in more advanced lesions showed that mutations in these same genes were shared between different regions of the same tumor and between primary and metastatic tumors, suggesting their trunk role in this disease.