Yes‐associated protein (YAP), a central effector in the Hippo pathway, is involved in the regulation of organ size, stem cell self‐renewal, and tissue regeneration. In this study, we observed YAP activation in patients with alcoholic steatosis, hepatitis, and cirrhosis. Accumulation of this protein in the nucleus was also observed in murine livers that were damaged after chronic‐plus‐single binge or moderate ethanol ingestion combined with carbon tetrachloride intoxication (ethanol/CCl4). To understand the role of this transcriptional coactivator in alcohol‐related liver injury, we knocked out the Yap1 gene in hepatocytes of floxed homozygotes through adeno‐associated virus (AAV8)‐mediated deletion utilizing Cre recombinase. Yap1 hepatocyte‐specific knockouts (KO) exhibited hemorrhage, massive hepatic necrosis, enhanced oxidative stress, elevated hypoxia, and extensive infiltration of CD11b+ inflammatory cells into hepatic microenvironments rich for connective tissue growth factor (Ctgf) during ethanol/CCl4‐induced liver damage. Analysis of whole‐genome transcriptomics indicated upregulation of genes involved in hypoxia and extracellular matrix (ECM) remodeling, whereas genes related to hepatocyte proliferation, progenitor cell activation, and ethanol detoxification were downregulated in the damaged livers of Yap1 KO. Acetaldehyde dehydrogenase (Aldh)1a1, a gene that encodes a detoxification enzyme for aldehyde substrates, was identified as a potential YAP target because this gene could be transcriptionally activated by a hyperactive YAP mutant. The ectopic expression of the human ALDH1A1 gene caused increase in hepatocyte proliferation and decrease in hepatic necrosis, oxidative stress, ECM remodeling, and inflammation during ethanol/CCl4‐induced liver damage. Taken together, these observations indicated that YAP was crucial for liver repair during alcohol‐associated injury. Its regulation of ALDH1A1 represents a new link in liver regeneration and detoxification.

Liver fibrosis is the common outcome of many chronic liver diseases, resulting from altered cell-cell and cell-matrix interactions that promote hepatic stellate cell (HSC) activation and excessive matrix production. This study aimed to investigate functions of cellular communication network factor 2 (CCN2)/Connective tissue growth factor (CTGF), an extracellular signaling modulator of the CYR61/CTGF/Nov (CCN) family, in liver fibrosis. Tamoxifen-inducible conditional knockouts in mice and hepatocyte-specific deletion of this gene in rats were generated using the Cre-lox system. These animals were subjected to peri-central hepatocyte damage caused by carbon tetrachloride. Potential crosstalk of this molecule with a new profibrotic pathway mediated by the Slit2 ligand and Roundabout (Robo) receptors was also examined. We found that Ccn2/Ctgf was highly upregulated in periportal hepatocytes during carbon tetrachloride-induced hepatocyte damage, liver fibrosis and cirrhosis in mice and rats. Overexpression of this molecule was observed in human hepatocellular carcinoma (HCC) that were surrounded with fibrotic cords. Deletion of the Ccn2/Ctgf gene significantly reduced expression of fibrosis-related genes including Slit2, a smooth muscle actin (SMA) and Collagen type I during carbon tetrachloride-induced liver fibrosis in mice and rats. In addition, Ccn2/Ctgf and its truncated mutant carrying the first three domains were able to interact with the 7th -9th epidermal growth factor (EGF) repeats and the C-terminal cysteine knot (CT) motif of Slit2 protein in cultured HSC and fibrotic murine livers. Ectopic expression of Ccn2/Ctgf protein upregulated Slit2, promoted HSC activation, and potentiated fibrotic responses following chronic intoxication by carbon tetrachloride. Moreover, Ccn2/Ctgf and Slit2 synergistically enhanced activation of phosphatidylinositol 3-kinase (PI3K) and AKT in primary HSC, whereas soluble Robo1-Fc chimera protein could inhibit these activities. These observations demonstrate conserved cross-species functions of Ccn2/Ctgf protein in rodent livers. This protein can be induced in hepatocytes and contribute to liver fibrosis. Its novel connection with the Slit2/Robo signaling may have therapeutic implications against fibrosis in chronic liver disease.

Targeted gene therapy using recombinant adeno-associated virus (rAAV) vectors is a potential therapeutic strategy for treating cancer, and tissue-specific promoters may help with tissue targeting. Medullary thyroid carcinoma (MTC) is a disease of the calcitonin secreting thyroid C cells, and calcitonin is highly expressed in MTC tumors compared to other cells. To target MTC cells, we evaluated an rAAV serotype 2 vector (rAAV2-pM+104-GFP) containing a modified calcitonin/calcitonin gene related peptide promoter (pM+104) and a green fluorescent protein (GFP) reporter gene. In vitro transduction experiments comparing the MTC TT cell line with non-MTC cell lines demonstrated that rAAV2-pM+104-GFP infection yielded significantly (p < 0.05) higher GFP expression in TT cells than in non-MTC cell lines (HEK293 and HeLa), and significantly higher expression than in TT cells infected with the positive control rAAV2-pCBA-GFP vector. The rAAV2-pCBA-GFP control vector included a well-characterized, ubiquitously expresses control promoter, the chicken beta actin promoter with a cytomegalovirus enhancer (pCBA). In vivo experiments using a TT cell xenograft tumor mouse model showed that tumors directly injected with 2 x 10 10 vg of rAAV2-pM+104-GFP vector resulted in GFP expression detected in 21.7% of cells, 48 hours after the injection. Furthermore, GFP expression was significantly higher for rAAV-pM +104-GFP treatments with a longer vector treatment duration and higher vector dose, with up to 52.6% (q < 0.05) GFP cells detected 72 hours after injecting 1x 10 11 vg/tumor. These data show that we have developed an rAAV vector with improved selectivity for MTC.

ALDHs consist of 24 families in the eukaryotic ALDH gene superfamily. Nineteen of them are found in the human genome and belong to the ALDH1-9, ALDH16, and ALDH18 families. 1 There are six isotype genes in the ALDH1 family (ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, ALDH1L1, and ALDH1L2). Among them, ALDH1A1, ALDH1A2, and ALDH1A3 encode cytosolic enzymes that oxidize retinal and aliphatic aldehydes. ALDH1A1 protein binds to retinaldehyde in great affinity and has been considered a major retinoid acid-metabolizing enzyme. 2 Cytosolic ALDH1A1 also plays a role in acetaldehyde oxidation and alcohol preference

Accumulation of senescent cells (SnCs) plays a causative role in many age-related diseases and has been implicated in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Senolytics that can selectively kill SnCs have the potential to be developed as therapeutics for these diseases. Here we reported the discovery of 753b, a BCL-xL proteolysis targeting chimera (PROTAC), as a potent and liver-tropic senolytic. We found that 753b can selectively clear senescent hepatocytes in aged mice and the STAM mice even though it can potently kill various SnCs in vitro. This is in part because 753b is enriched in the liver after its administration by ip injection. Moreover, 753b treatment can effectively reduce the development of non-alcoholic steatohepatitis (NASH), liver fibrosis, and hepatocellular carcinoma (HCC) in the STAM mice. These findings suggest that 753b has the potential to be developed as a novel therapeutic for NAFLD and NASH-driven HCC. Citation Format: Yang Yang, Natacha Jn-Simon, Wanyi Hu, Peiyi Zhang, Guangrong Zheng, Liya Pi, Yonghan He, Daohong Zhou. A liver-tropic BCL-xL PROTAC effectively clears senescent hepatocytes and prevents NASH-driven HCC in mice [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr B009.