Specific expression and regulation of hepassocin in the liver and down-regulation of the correlation of HNF1alpha with decreased levels of hepassocin in human hepatocellular carcinoma

FGL1: a novel biomarker and target for non-small cell lung cancer, promoting tumor progression and metastasis through KDM4A/STAT3 transcription mechanism

Non-small cell lung cancer (NSCLC) is characterized by a high incidence rate and poor prognosis worldwide. A deeper insight into the pathogenesis of NSCLC and identification of novel therapeutic targets are essential to improve the prognosis of NSCLC. In this study, we revealed that fibrinogen-like protein 1 (FGL1) promotes proliferation, migration, and invasion of NSCLC cells. Mechanistically, we found that Stat3 acts as a transcription factor and can be recruited to the FGL1 promoter, enhancing FGL1 promoter activity. Lysine-specific demethylase 4A (KDM4A) interacts with Stat3 and facilitates the removal of methyl groups from H3K9me3, thereby enhancing Stat3-mediated transcription of FGL1. Furthermore, we observed that Stat3 and KDM4A promote NSCLC cell proliferation, migration, and invasion partly by upregulating FGL1 expression. Additionally, the expression of FGL1 was significantly higher in cancer tissues (n = 90) than in adjacent non-cancerous tissues (n = 90). Furthermore, patients with high FGL1 expression had a shorter overall survival (OS) compared to those with low FGL1 expression. We measured the expression levels of FGL1 on circulating tumor cells (CTCs) in 65 patients and found that patients with a dynamic decrease in FGL1 expression on CTCs exhibited a better therapeutic response. These findings suggest that the dynamic changes in FGL1 expression can serve as a potential biomarker for predicting treatment efficacy in NSCLC. Overall, this study revealed the significant role and regulatory mechanisms of FGL1 in the development of NSCLC, suggesting its potential as a therapeutic target for patients with NSCLC. Future studies should provide more personalized and effective treatment options for patients with NSCLC to improve clinical outcomes.

Fibrinogen-like 1: A hepatokine linking liver physiology to hematology

A recent study identified the critical contribution of the hepatokine FGL1 to the regulation of iron metabolism during the recovery from anemia. FGL1 is secreted by hepatocytes in response to hypoxia to sequester BMP ligands and repress the transcription of the iron-regulatory hormone hepcidin. This process ensures the proper supply of iron to the bone marrow for new red blood cell synthesis and the restoration of physiological oxygen levels. FGL1 may therefore contribute to the recovery from common anemias and cause iron overload in chronic anemias with ineffective erythropoiesis, such as ß-thalassemia, dyserythropoietic anemia, and myelodysplastic syndromes. However, FGL1 has also been described as a regulator of hepatocyte proliferation, glucose homeostasis, and insulin signaling, as well as a mediator of liver steatosis and immune evasion. Chronic exposure to elevated levels of FGL1 during anemia may therefore have systemic metabolic effects besides iron regulation and erythropoiesis. Here, we are providing an overview of the proposed functions of FGL1 in physiology and pathophysiology.

FGL1 and FGL2: emerging regulators of liver health and disease

Liver disease is a complex group of diseases with high morbidity and mortality rates, emerging as a major global health concern. Recent studies have highlighted the involvement of fibrinogen-like proteins, specifically fibrinogen-like protein 1 (FGL1) and fibrinogen-like protein 2 (FGL2), in the regulation of various liver diseases. FGL1 plays a crucial role in promoting hepatocyte growth, regulating lipid metabolism, and influencing the tumor microenvironment (TME), contributing significantly to liver repair, non-alcoholic fatty liver disease (NAFLD), and liver cancer. On the other hand, FGL2 is a multifunctional protein known for its role in modulating prothrombin activity and inducing immune tolerance, impacting viral hepatitis, liver fibrosis, hepatocellular carcinoma (HCC), and liver transplantation. Understanding the functions and mechanisms of fibrinogen-like proteins is essential for the development of effective therapeutic approaches for liver diseases. Additionally, FGL1 has demonstrated potential as a disease biomarker in radiation and drug-induced liver injury as well as HCC, while FGL2 shows promise as a biomarker in viral hepatitis and liver transplantation. The expression levels of these molecules offer exciting prospects for disease assessment. This review provides an overview of the structure and roles of FGL1 and FGL2 in different liver conditions, emphasizing the intricate molecular regulatory processes and advancements in targeted therapies. Furthermore, it explores the potential benefits and challenges of targeting FGL1 and FGL2 for liver disease treatment and the prospects of fibrinogen-like proteins as biomarkers for liver disease, offering insights for future research in this field.

Role of Fibrinogen-like Protein 1 in Tumor Recurrence Following Hepatectomy

Partial hepatectomy is a first-line treatment for hepatocellular carcinoma. Within 2 weeks following partial hepatectomy, specific molecular pathways are activated to promote liver regeneration. Nevertheless, residual microtumors may also exploit these pathways to reappear and metastasize. Therapeutically targeting molecules that are differentially regulated between normal cells and malignancies, such as fibrinogen-like protein 1 (FGL1), appears to be an effective approach. The potential functions of FGL1 in both regenerative and malignant cells are discussed within the ambit of this review. While FGL1 is normally elevated in regenerative hepatocytes, it is normally downregulated in malignant cells. Hepatectomy does indeed upregulate FGL1 by increasing the release of transcription factors that promote FGL1, including HNF-1α and STAT3, and inflammatory effectors, such as TGF-β and IL6. This, in turn, stimulates certain proliferative pathways, including EGFR/Src/ERK. Hepatectomy alters the phase transition of highly differentiated hepatocytes from G0 to G1, thereby transforming susceptible cells into cancerous ones. Activation of the PI3K/Akt/mTOR pathway by FGL1 allele loss on chromosome 8, a tumor suppressor area, may also cause hepatocellular carcinoma. Interestingly, FGL1 is specifically expressed in the liver via HNF-1α histone acetylase activity, which triggers lipid metabolic reprogramming in malignancies. FGL1 might also be involved in other carcinogenesis processes such as hypoxia, epithelial-mesenchymal transition, immunosuppression, and sorafenib-mediated drug resistance. This study highlights a research gap in these disciplines and the necessity for additional research on FGL1 function in the described processes.

SPOP inhibits HBV transcription and replication by ubiquitination and degradation of HNF1α

Hepatitis B virus (HBV) infection remains a significant public health burden worldwide. The persistence of covalently closed circular DNA (cccDNA) within the nucleus of infected hepatocytes is responsible for the failure of antiviral treatments. The ubiquitin proteasome system (UPS) has emerged as a promising antiviral target, as it can regulate HBV replication by promoting critical protein degradation in steps of viral life cycle. Speckle-type POZ protein (SPOP) is a critical adaptor for Cul3-RBX1 E3 ubiquitin ligase complex, but the effect of SPOP on HBV replication is less known. Here, we identified SPOP as a novel host antiviral factor against HBV infection. SPOP overexpression significantly inhibited the transcriptional activity of HBV cccDNA without affecting cccDNA level in HBV-infected HepG2-NTCP and primary human hepatocyte cells. Mechanism studies showed that SPOP interacted with hepatocyte nuclear factor 1α (HNF1α), and induced HNF1α degradation through host UPS pathway. Moreover, the antiviral role of SPOP was also confirmed in vivo. Together, our findings reveal that SPOP is a novel host factor which inhibits HBV transcription and replication by ubiquitination and degradation of HNF1α, providing a potential therapeutic strategy for the treatment of HBV infection.

FBXO38 mediates FGL1 ubiquitination and degradation to enhance cancer immunity and suppress inflammation

Upregulation of FGL1 helps tumors escape from immune surveillance, and therapeutic antibodies targeting FGL1 have potential as another immune checkpoint inhibitor. However, the underlying mechanism of high FGL1 protein level in cancers is not well defined. Here, we report that FBXO38 interacts with and ubiquitylates FGL1 to negatively regulate its stability and to mediate cancer immune response. Depletion of FBXO38 markedly augments FGL1 abundance, not only suppressing CD8+ T cell infiltration and enhancing immune evasion of tumor but also increasing inflammation in mice. Importantly, we observe a negative correlation of FBXO38 with FGL1 and IL-6 in non-small cell lung cancer specimens. FGL1 and IL-6 levels positively correlate with TNM (tumor, lymph node, metastasis) stages, while FBXO38 and the infiltrating CD8+ T cells negatively correlate with TNM stages. Our study identifies a mechanism regulating FGL1 stability and a target to enhance the immunotherapy and suggests that the combination of anti-FGL1 and anti-IL-6 is a potential therapeutic strategy for cancer immunotherapy.

Lysine 117 Residue Is Essential for the Function of the Hepatocyte Nuclear Factor 1α

Hepatocyte nuclear factor 1α (HNF1α) plays essential roles in controlling development and metabolism; its mutations are clearly linked to the occurrence of maturity-onset diabetes of the young (MODY3) in humans. Lysine 117 (K117) to glutamic acid (E117) mutation in the HNF1α gene has been clinically associated with MODY3, but no functional data on this variant are available. Here, we addressed the role of lysine 117 in HNF1α function using a knock-in animal model and site-directed mutagenesis. HNF1α K117E homozygous mice exhibited dwarfism, hepatic dysfunction, renal Fanconi syndrome, and progressive wasting syndrome. These phenotypes were very similar to those of mice with complete HNF1α deficiency, suggesting that K117 is critical to HNF1α functions. K117E homozygotes developed diabetes in the early postnatal period. The relative deficiency of serum insulin levels and the normal response to insulin treatment in homozygous mice were markedly similar to those in the MODY3 disorder in humans. Moreover, K117E heterozygous mutant causes age-dependent glucose intolerance, which is similar to the pathogenesis of MODY3 as well. K117 mutants significantly reduced the overall transactivation and DNA binding capacity of HNF1α by disrupting dimerization. Collectively, our findings reveal a previously unappreciated role of POU domain of HNF1α in homodimerization and provide important clues for identifying the molecular basis of HNF1α-related diseases such as MODY3.

ARTICLE HIGHLIGHTS

HNF1α K117E homozygous mice exhibited dwarfism, hepatic dysfunction, renal Fanconi syndrome, and progressive wasting syndrome. K117E homozygotes developed diabetes in the early postnatal period. K117E heterozygous mutant causes age-dependent glucose intolerance, which is similar to the pathogenesis of maturity-onset diabetes of the young. K117 mutants significantly reduced the overall transactivation and DNA binding capacity of HNF1α by disrupting dimerization.

Compensatory Increase of Serum Hepassocin Protects Hyperthyroidism-Induced Hepatic Dysfunction

Hepatic dysfunction is commonly observed in subjects with hyperthyroidism. Hepassocin is a hepatokine playing an important role in metabolic diseases and exhibiting a hepatic protective effect. Nevertheless, the relationship between hepassocin and hyperthyroidism was still unknown. In the present study, a total of 36 subjects with Graves' disease were enrolled, and we found that the alanine aminotransferase (ALT) levels were significantly decreased in parallel with the decrement in serum hepassocin concentrations at 6 months after standard treatment for hyperthyroidism. In addition, HepG2 cell line was used to investigate the role of hepassocin in hyperthyroidism-induced hepatic dysfunction. Treatment of hepassocin recombinant protein in HepG2 cells dose-dependently decreased triiodothyronine (T3)-induced ALT and aspartate aminotransferase (AST) elevation. Moreover, hepassocin significantly increased the expression of phosphoenolpyruvate carboxykinase (PEPCK) in a dose-dependent manner. Deletion of hepassocin in HepG2 cells reversed the effects of T3 on PEPCK expressions. Furthermore, we found that T3 increased the expression of hepassocin through a hepatocyte nuclear factor 1α-dependent pathway. Taken together, these results indicated a compensatory increase in serum hepassocin might have a protective role in hyperthyroidism-induced hepatic dysfunction.

Protective Role of Hepassocin against Hepatic Endoplasmic Reticulum Stress in Mice

Hepassocin (HPS) is a hepatokine that has multiple proposed physiological functions. Some of the biological processes in which it is involved are closely related to endoplasmic reticulum (ER) stress, but the role of HPS in the regulation of ER stress remains unclear. Here, we demonstrated that HPS transcription is induced by the protein kinase RNA-like ER kinase (PERK)/activating transcription factor 4 (ATF4) cascade upon ER stress in hepatocytes. Additionally, fasting/refeeding also induced HPS expression in mice liver. The loss of HPS sensitizes hepatocytes to ER stress-related cytotoxicity in vitro, whereas HPS treatment altered these phenotypes. HPS deficiency exacerbates fasting/refeeding-induced ER stress in vivo. The preliminary administration of HPS ameliorates liver steatosis, cell death, and inflammation in mice injected with tunicamycin (TM). The improvement of HPS can be observed even if HPS protein is injected after TM treatment. Furthermore, the administration of an ER stress inhibitor alleviated steatohepatitis in methionine- and choline-deficient (MCD) diet-fed HPS-deficient mice. These results suggest that HPS protects hepatocytes from physiological and pathological ER stress, and that the inactivation of HPS signaling aggravating ER stress may be a novel mechanism that drives the development of steatohepatitis. The protective mechanism of HPS against ER stress in hepatocytes was associated with the regulation of ER calcium handling, and the suppression of calcium influx release from ER upon stressor treatment. Collectively, our findings indicate that HPS may act in a negative feedback fashion to regulate hepatic ER stress and protect hepatocytes from ER stress-related injury. HPS has the potential to be a candidate drug for the treatment of ER stress-related liver injury.

HPS protects the liver against steatosis, cell death, inflammation, and fibrosis in mice with steatohepatitis

Hepassocin (HPS) is a hepatokine associated with metabolic regulation and development of non-alcoholic steatohepatitis (NASH). However, previous reports on HPS are controversial and its true function is not yet understood. Here, we demonstrated that hepatic HPS expression levels were upregulated in short-term feeding and downregulated in long-term feeding in high-fat diet (HFD)- and methionine- and choline-deficient (MCD) diet-fed mice, as well as in genetically obese (ob/ob) mice. HFD- and MCD-induced hepatic steatosis, inflammation, apoptosis, and fibrosis were more pronounced in HPS knockout mice than in the wild-type mice. Moreover, HPS depletion aggravated HFD-induced insulin resistance. By contrast, HPS administration improved MCD- or HFD-induced liver phenotypes and insulin resistance in HPS knockout and wild-type mice. Mechanistic studies revealed that MCD-induced hepatic oxidative stress was significantly increased by HPS deficiency and could be attenuated by HPS administration. Furthermore, palmitic acid-induced lipid accumulation and oxidative stress were exclusively enhanced in HPS knockout hepatocytes and diminished by HPS cotreatment. These data suggest that HPS ameliorates NASH in mice, at least in part, by inhibiting the oxidative stress. HPS expression levels are downregulated in human fatty liver tissues, suggesting that it may play an important protective role in NASH. Collectively, our findings provide clear genetic evidence that HPS has beneficial effects on the development of steatohepatitis in mice and suggest that upregulating HPS signaling may represent an effective treatment strategy for NASH.

Fibrinogen-Like Protein 1 as a Novel Biomarker of Psoriasis Severity

Background

Psoriasis is an immune-mediated chronic systemic inflammatory skin disease whose diagnosis and severity assessment pose challenges for clinicians worldwide. The use of serum biomarkers facilitates the early diagnosis and treatment of psoriasis.

Methods

This case–control study compared tumor necrosis factor α (TNF-α), interleukin (IL)-6, IL-17, IL-10, and fibrinogen-like protein 1 (FGL1) levels of 139 untreated psoriasis patients and 140 healthy controls. Serum samples were collected, and enzyme-linked immunosorbent assays were performed to quantify their levels. Subgroups were analyzed according to abnormal lipid metabolism status.

Results

Compared to controls, patients with psoriasis exhibited lower concentrations of serum TNF-α, IL-17, and FGL1 (P < 0.05). A correlation analysis showed that FGL1 was inversely correlated with high-density lipoprotein cholesterol and IL-17 in the psoriatic state. Stepwise multiple regression analysis revealed that FGL1 and total cholesterol were the independent determinants of Psoriasis Area and Severity Index (PASI) score in psoriasis patients. The area under the receiver operating characteristic curve of FGL1 assessing moderate-to-severe psoriasis and mild psoriasis was 0.70, while the area under the curve (AUC) assessing severe psoriasis and mild-to-moderate psoriasis was 0.67, better than that of IL-17. In addition, FGL1, but not IL-17, was able to identify psoriasis with abnormal lipid metabolism to a certain extent (AUC = 0.60).

Conclusion

In conclusion, serum FGL1 may be a promising biomarker for diagnosing and staging psoriasis. It may also be involved in its progression and comorbid abnormal lipid metabolism.

The correlation of fibrinogen-like protein-1 expression with the progression and prognosis of hepatocellular carcinoma

BACKGROUND

Fibrinogen-like-protein 1 (FGL1), a member of the fibrinogen-related protein (FREP) family, is a major ligand of the immune inhibitory receptor lymphocyte-activation gene 3 (LAG-3). While FGL1 is strongly implicated in the development and prognosis of a variety of diseases, its role in hepatocellular carcinoma (HCC) is still disputed. Therefore, the role of FGL1 expression in the progression and prognosis of HCC was investigated.

METHODS AND RESULTS

In the present study, bioinformatics analysis was first used to probe the expression profile of FGL1 in multiple malignant tumor tissues and paired normal tissues, and to explore the possible relationship between FGL1 and prognosis of HCC patients. Thereafter, the expression levels of FGL1 were determined and compared in human HCC cell lines, HCC tissues, peri-tumor tissues and normal liver tissues by western blot analysis. Furthermore, tissue microarrays were used to detect the expression of FGL1 through immunohistochemical staining and to verify whether the FGL1 expression level was associated with clinicopathological features and the prognosis of HCC patients. The results showed that FGL1 was downregulated significantly in most of the HCC cells lines and HCC tissues, corresponding to the results of the bioinformatics and western blot analyses. FGL1 expression level in HCC was found to be correlated to Edmondson grade and metastasis of the HCC. Additionally, high FGL1 expression was associated with better overall survival in HCC patients, suggesting that FGL1 could function as a tumor suppressor.

CONCLUSIONS

The expression level of FGL1 can be correlated with the progression and prognosis of HCC, suggesting its potential as a prognostic biomarker.

Implication of the hepatokine, fibrinogen-like protein 1 in liver diseases, metabolic disorders and cancer: The need to harness its full potential

Fibrinogen-like protein 1 (FGL1) is a novel hepatokine that forms part of the fibrinogen superfamily. It is predominantly expressed in the liver under normal physiological conditions. When the liver is injured by external factors, such as chemical drugs and radiation, FGL1 acts as a protective factor to promote the growth of regenerated cells. However, elevated hepatic FGL1 under high fat conditions can cause lipid accumulation and inflammation, which in turn trigger the development of non-alcoholic fatty liver disease, diabetes, and obesity. FGL1 is also involved in the regulation of insulin resistance in adipose tissues and skeletal muscles as a means of communication between the liver and other tissues. In addition, the abnormally changed FGL1 levels in the plasma of cancer patients make it a potential predictor of cancer incidence in clinical practice. FGL1 was recently identified as a major functional ligand of the immune inhibitory receptor, lymphocyte-activation gene 3 (LAG3), thus making it a promising target for cancer immunotherapy except for the classical programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis. Despite the potential of FGL1 as a new cancer biomarker and therapeutic target, there are few related studies and much of what has been reported are superficial and lack depth and particularity. Therefore, elucidating the role and underlying mechanisms of FGL1 could be crucial for the development of promising diagnostic and therapeutic strategies for related diseases. Here, we provide a comprehensive review of the cellular mechanisms and clinical prospects of FGL1 in the prevention and treatment of liver diseases, metabolic disorders and cancer, and proffer suggestions for future studies.

Hepatokines and Non-Alcoholic Fatty Liver Disease: Linking Liver Pathophysiology to Metabolism

The liver plays a key role in maintaining energy homeostasis by sensing and responding to changes in nutrient status under various metabolic conditions. Recently highlighted as a major endocrine organ, the contribution of the liver to systemic glucose and lipid metabolism is primarily attributed to signaling crosstalk between multiple organs via hepatic hormones, cytokines, and hepatokines. Hepatokines are hormone-like proteins secreted by hepatocytes, and a number of these have been associated with extra-hepatic metabolic regulation. Mounting evidence has revealed that the secretory profiles of hepatokines are significantly altered in non-alcoholic fatty liver disease (NAFLD), the most common hepatic manifestation, which frequently precedes other metabolic disorders, including insulin resistance and type 2 diabetes. Therefore, deciphering the mechanism of hepatokine-mediated inter-organ communication is essential for understanding the complex metabolic network between tissues, as well as for the identification of novel diagnostic and/or therapeutic targets in metabolic disease. In this review, we describe the hepatokine-driven inter-organ crosstalk in the context of liver pathophysiology, with a particular focus on NAFLD progression. Moreover, we summarize key hepatokines and their molecular mechanisms of metabolic control in non-hepatic tissues, discussing their potential as novel biomarkers and therapeutic targets in the treatment of metabolic diseases.

Recombinant Human HPS Protects Mice and Nonhuman Primates from Acute Liver Injury

Acute liver injury shares a common feature of hepatocytes death, immune system disorders, and cellular stress. Hepassocin (HPS) is a hepatokine that has ability to promote hepatocytes proliferation and to protect rats from D-galactose (D-Gal)- or carbon tetrachloride (CCl4)-induced liver injury by stimulating hepatocytes proliferation and preventing the high mortality rate, hepatocyte death, and hepatic inflammation. In this paper, we generated a pharmaceutical-grade recombinant human HPS using mammalian cells expression system and evaluated the effects of HPS administration on the pathogenesis of acute liver injury in monkey and mice. In the model mice of D-galactosamine (D-GalN) plus lipopolysaccharide (LPS)-induced liver injury, HPS treatment significantly reduced hepatocyte death and inflammation response, and consequently attenuated the development of acute liver failure. In the model monkey of D-GalN-induced liver injury, HPS administration promoted hepatocytes proliferation, prevented hepatocyte apoptosis and oxidation stress, and resulted in amelioration of liver injury. Furthermore, the primary pharmacokinetic study showed natural HPS possesses favorable pharmacokinetics; the acute toxicity study indicated no significant changes in behavioral, clinical, or histopathological parameters of HPS-treated mice, implying the clinical potential of HPS. Our results suggest that exogenous HPS has protective effects on acute liver injury in both mice and monkeys. HPS or HPS analogues and mimetics may provide novel drugs for the treatment of acute liver injury.

Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Immune checkpoint therapy has achieved significant efficacy by blocking inhibitory pathways to release the function of T lymphocytes. In the clinic, anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) have progressed to first-line monotherapies in certain tumor types. However, the efficacy of anti-PD-1/PD-L1 mAbs is still limited due to toxic side effects and de novo or adaptive resistance. Moreover, other immune checkpoint target and biomarkers for therapeutic response prediction are still lacking; as a biomarker, the PD-L1 (CD274, B7-H1) expression level is not as accurate as required. Hence, it is necessary to seek more representative predictive molecules and potential target molecules for immune checkpoint therapy. Fibrinogen-like protein 1 (FGL1) is a proliferation- and metabolism-related protein secreted by the liver. Multiple studies have confirmed that FGL1 is a newly emerging checkpoint ligand of lymphocyte activation gene 3 (LAG3), emphasizing the potential of targeting FGL1/LAG3 as the next generation of immune checkpoint therapy. In this review, we summarize the substantial regulation mechanisms of FGL1 in physiological and pathological conditions, especially tumor epithelial to mesenchymal transition, immune escape and immune checkpoint blockade resistance, to provide insights for targeting FGL1 in cancer treatment.

Fibrinogen-Like Protein 1 Modulates Sorafenib Resistance in Human Hepatocellular Carcinoma Cells

Despite liver cancer being the second-leading cause of cancer-related death worldwide, few systemic drugs have been approved. Sorafenib, the first FDA-approved systemic drug for unresectable hepatocellular carcinoma (HCC), is limited by resistance. However, the precise mechanisms underlying this phenomenon are unknown. Since fibrinogen-like 1 (FGL1) is involved in HCC progression and upregulated after anticancer therapy, we investigated its role in regulating sorafenib resistance in HCC. FGL1 expression was assessed in six HCC cell lines (HepG2, Huh7, Hep3B, SNU387, SNU449, and SNU475) using western blotting. Correlations between FGL1 expression and sorafenib resistance were examined by cell viability, colony formation, and flow cytometry assays. FGL1 was knocked-down to confirm its effects on sorafenib resistance. FGL1 expression was higher in HepG2, Huh7, and Hep3B cells than in SNU387, SNU449, and SNU475 cells; high FGL1-expressing HCC cells showed a lower IC₅₀ and higher sensitivity to sorafenib. In Huh7 and Hep3B cells, FGL1 knockdown significantly increased colony formation by 61% (p = 0.0013) and 99% (p = 0.0002), respectively, compared to that in controls and abolished sorafenib-induced suppression of colony formation, possibly by modulating ERK and autophagy signals. Our findings demonstrate that sorafenib resistance mediated by FGL1 in HCC cells, suggesting FGL1 as a potential sorafenib-resistance biomarker and target for HCC therapy.

Involvement of LH3 and GLT25D1 for glucosyl-galactosyl-hydroxylation on non-collagen-like domain of FGL1

Glucosyl-galactosyl-hydroxylation (GGH) is one type of post-translational modification, which is mainly observed in collagen-like domain-containing proteins. Using LC-MS/MS analysis, we found a GGH-like modification at Lys65 of fibrinogen-like protein 1 (FGL1), although it does not contain a collagen-like domain. To identify the glycosyltransferases responsible for this modification, we established LH3/GLT25D1-knockout FGL1-overexpressing HT1080 cell lines. The result showed that knockout of LH3 or GLT25D1 significantly inhibited the glycosylation. Furthermore, deficiency of GGH by point mutation of the FGL1 protein or knockout of the GGH-related glycosyltransferase reduced FGL1 protein levels. Taken together, these data indicate that Lys65 of FGL1 is glucosyl-galactosyl-hydroxylated by LH3 and GLT25D1. Our results provide novel insights to regulate various FGL1 functions.

Metabolic Spectrum of Liver Failure in Type 2 Diabetes and Obesity: From NAFLD to NASH to HCC

Liver disease is the spectrum of liver damage ranging from simple steatosis called as nonalcoholic fatty liver disease (NAFLD) to hepatocellular carcinoma (HCC). Clinically, NAFLD and type 2 diabetes coexist. Type 2 diabetes contributes to biological processes driving the severity of NAFLD, the primary cause for development of chronic liver diseases. In the last 20 years, the rate of non-viral NAFLD/NASH-derived HCC has been increasing rapidly. As there are currently no suitable drugs for treatment of NAFLD and NASH, a class of thiazolidinediones (TZDs) drugs for the treatment of type 2 diabetes is sometimes used to improve liver failure despite the risk of side effects. Therefore, diagnosis, prevention, and treatment of the development and progression of NAFLD and NASH are important issues. In this review, we will discuss the pathogenesis of NAFLD/NASH and NAFLD/NASH-derived HCC and the current promising pharmacological therapies of NAFLD/NASH. Further, we will provide insights into "adipose-derived adipokines" and "liver-derived hepatokines" as diagnostic and therapeutic targets from NAFLD to HCC.

Eicosapentaenoic Acid Inhibits KRAS Mutant Pancreatic Cancer Cell Growth by Suppressing Hepassocin Expression and STAT3 Phosphorylation

Background: The oncogenic Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation was reported to be the signature genetic event in most cases of pancreatic ductal adenocarcinoma (PDAC). Hepassocin (HPS/FGL1) is involved in regulating lipid metabolism and the progression of several cancer types; however, the underlying mechanism of HPS/FGL1 in the KRAS mutant PDAC cells undergoing eicosapentaenoic acid (EPA) treatment remains unclear. Methods: We measured HPS/FGL1 protein expressions in a human pancreatic ductal epithelial (HPNE) normal pancreas cell line, a KRAS-wild-type PDAC cell line (BxPC-3), and KRAS-mutant PDAC cell lines (PANC-1, MIA PaCa-2, and SUIT-2) by Western blot methods. HEK293T cells were transiently transfected with corresponding KRAS-expressing plasmids to examine the level of HPS expression with KRAS activation. We knocked-down HPS/FGL1 using lentiviral vectors in SUIT-2 cells and measured the cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and clonogenicity assays. Furthermore, a lipidomic analysis was performed to profile changes in lipid metabolism after HPS/FGL1 knockdown. Results: We found that the HPS/FGL1 level was significantly upregulated in KRAS-mutated PDAC cells and was involved in KRAS/phosphorylated (p)-signal transduction and activator of transcription 3 (STAT3) signaling, and the knockdown of HPS/FGL1 in SUIT-2 cells decreased cell proliferation through increasing G₂/M cell cycle arrest and cyclin B1 expression. In addition, the knockdown of HPS/FGL1 in SUIT-2 cells significantly increased omega-3 polyunsaturated fatty acids (PUFAs) and EPA production but not docosahexaenoic acid (DHA). Moreover, EPA treatment in SUIT-2 cells reduced the expression of de novo lipogenic protein, acetyl coenzyme A carboxylase (ACC)-1, and decreased p-STAT3 and HPS/FGL1 expressions, resulting in the suppression of cell viability. Conclusions: Results of this study indicate that HPS is highly expressed by KRAS-mutated PDAC cells, and HPS/FGL1 plays a crucial role in altering lipid metabolism and increasing cell growth in pancreatic cancer. EPA supplements could potentially inhibit or reduce ACC-1-involved lipogenesis and HPS/FGL1-mediated cell survival in KRAS-mutated pancreatic cancer cells.

Hepatokines and adipokines in NASH-related hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) is increasing in industrialised societies; this is likely secondary to the increasing burden of non-alcoholic fatty liver disease (NAFLD), its progressive form non-alcoholic steatohepatitis (NASH), and the metabolic syndrome. Cumulative studies suggest that NAFLD-related HCC may also develop in non-cirrhotic livers. However, prognosis and survival do not differ between NAFLD- or virus-associated HCC. Thus, research has increasingly focused on NAFLD-related risk factors to better understand the biology of hepatocarcinogenesis and to develop new diagnostic, preventive, and therapeutic strategies. One important aspect thereof is the role of hepatokines and adipokines in NAFLD/NASH-related HCC. In this review, we compile current data supporting the use of hepatokines and adipokines as potential markers of disease progression in NAFLD or as early markers of NAFLD-related HCC. While much work must be done to elucidate the mechanisms and interactions underlying alterations to hepatokines and adipokines, current data support the possible utility of these factors - in particular, angiopoietin-like proteins, fibroblast growth factors, and apelin - for detection or even as therapeutic targets in NAFLD-related HCC.

Circulating hepassocin level in patients with stable angina is associated with fatty liver and renal function

Background: Chronic kidney disease (CKD) is a major risk factor for coronary artery disease and it is often associated with hepatic steatosis. Hepassocin (also known as hepatocyte-derived fibrinogen related protein or fibrinogen-like 1) is a novel hepatokine that causes hepatic steatosis and induces insulin resistance. However, the role of hepassocin in renal function status remains unclear. Our objective was to investigate the association of plasma hepassocin level with fatty liver and renal function status in patients with stable angina. Methods: Plasma hepassocin levels were determined by enzyme-linked immunosorbent assays in 395 consecutive patients with stable angina. Renal function was defined as an estimated glomerular filtration rate (eGFR). Fatty liver was defined by ultrasonography and fibrosis-4 (FIB-4) index. Results: With increasing hepassocin tertiles, patients had higher prevalence of fatty live, an increased waist-to-hip ratio, and neutrophil count, monocyte count, and FIB-4 index, higher levels of uric acid, blood urine nitrogen and higher sensitivity C-reactive protein. They also had incrementally lower eGFR, serum hemoglobin and albumin levels. In multiple linear stepwise regression analysis, only eGFR was significantly independent negatively associated with plasma hepassocin levels. Conclusion: Our results indicate that circulating hepassocin in patients with stable angina is associated with fatty liver and renal function, which suggests that increased plasma hepassocin may be involved in the pathogenesis of fatty liver and CKD.

Fibrinogen-Like Protein 1 Is a Novel Biomarker for Predicting Disease Activity and Prognosis of Rheumatoid Arthritis

Rheumatoid arthritis (RA), afflicting over 1% of the population, is an inflammatory joint disease leading to cartilage damage and ultimately impaired joint function. Disease-modifying anti-rheumatic drugs are considered as the first-line treatment to inhibit the progression of RA, and the treatment depends on the disease status assessment. The disease activity score 28 as clinical gold standard is extensively used for RA assessment, but it has the limitations of delayed assessment and the need for specialized expertise. It is necessary to discover biomarkers that can precisely monitor disease activity, and provide optimized treatment for RA patients. A total of 1,244 participants from two independent centers were divided into five cohorts. Cohorts 1–4 constituted sera samples of moderate to high active RA, low active RA, RA in remission and healthy subjects. Cohort 5 consisted of sera of RA, osteoarthritis (OA), ankylosing spondylitis (AS), systemic lupus erythematosus (SLE), primary Sjogren's syndrome (pSS) and healthy subjects. Biomarkers were found from cohorts 1–2 (screening sets), cohort 3 (discovery and external validation sets), cohort 4 (drug intervention set) and cohort 5 (biomarker-specific evaluation set). We found 68 upregulated and 74 downregulated proteins by TMT-labeled proteomics in cohort 1, and fibrinogen-like protein 1 (FGL1) had the highest area under the receiver operating characteristic curve (AUC) values in cohort 2. In cohort 3, in cross-comparison among moderate/high active RA, low active RA, RA in remission and healthy subjects, FGL1 had AUC values of approximately 0.9000 and predictive values of 90%. Additionally, FGL1 had a predictive value of 91.46% for moderate/high active RA vs. remission/low active RA and 80.77% for RA in remission vs. low active RA in cohort 4. Importantly, FGL1 levels had no significant difference in OA and AS compared with healthy persons. The concentrations in SLE and pSS were improved, but approximately 3-fold lower than that in active RA in cohort 5. In summary, FGL1 is a novel and specific biomarker that could be clinically useful for predicting progression of RA.

HMGB1 Inhibits HNF1A to Modulate Liver Fibrogenesis via p65/miR-146b Signaling

High mobility group box 1 (HMGB1) is essential for the pathogenesis of liver injury and liver fibrosis. We previously revealed that miR-146b promotes hepatic stellate cells (HSCs) activation and proliferation. Nevertheless, the potential mechanisms are still unknown. Herein, HMGB1 increased HSCs proliferation and COL1A1 and α-SMA protein levels. However, the knockdown of miR-146b inhibited HSCs proliferation and COL1A1 and α-SMA protein levels induced via HMGB1 treatment. miR-146b was upregulated by HMGB1 and miR-146b targeted hepatocyte nuclear factor 1A (HNF1A) 3'-untranslated region (3'UTR) to modulate its expression negatively. Further, we confirmed that HMGB1 might elicit miR-146b expression via p65 within HSCs. Knockdown or block of HMGB1 relieved the CCl₄-induced liver fibrosis. In fibrotic liver tissues, miR-146b expression was positively correlated with p65 mRNA, but HNF1A mRNA was inversely correlated with p65, and miR-146b expression. In summary, our findings suggest that HMGB1/p65/miR-146b/HNF1A signaling exerts a crucial effect on liver fibrogenesis via the regulation of HSC function.

FGL1 regulates acquired resistance to Gefitinib by inhibiting apoptosis in non-small cell lung cancer

Background

This study investigated the role of fibrinogen-like protein 1 (FGL1) in regulating gefitinib resistance of PC9/GR non-small cell lung cancer (NSCLC).

Methods

The effect of different concentrations of gefitinib on cell proliferation were evaluated using the CCK-8 assay. FGL1 expression in the normal human bronchial epithelial cell line Beas-2B, as well as four lung tumor cell lines, H1975, A549, PC9, and PC9/GR, was investigated by using western blotting and qRT-PCR. FGL1 was knocked down using small interfering RNA to evaluate the effects of FGL1 on PC9 and PC9/GR. The correlation between FGL1 expression and gefitinib resistance was determined in vitro via CCK-8 and colony formation assays, and flow cytometry and in vivo via flow cytometry and immunohistochemistry.

Results

FGL1 expression was significantly upregulated in non-small cell lung cancer cells with EGFR mutation and higher in the gefitinib-resistant NSCLC cell line PC9/GR than in the gefitinib-sensitive NSCLC cell line PC9. Further, FGL1 expression in PC9 and PC9/GR cells increased in response to gefitinib treatment in a dose-dependent manner. Knockdown of FGL1 suppressed cell viability, reduced the gefitinib IC50 value, and enhanced apoptosis in PC9 and PC9/GR cells upon gefitinib treatment. Mouse xenograft experiments showed that FGL1 knockdown in PC9/GR tumor cells enhanced the inhibitory and apoptosis-inducing actions of gefitinib. The potential mechanism of gefitinib in inducing apoptosis of PC9/GR cells involves inhibition of PARP1 and caspase 3 expression via suppression of FGL1.

Conclusions

FGL1 confers gefitinib resistance in the NSCLC cell line PC9/GR by regulating the PARP1/caspase 3 pathway. Hence, FGL1 is a potential therapeutic target to improve the treatment response of NSCLC patients with acquired resistance to gefitinib.

The Liver as an Endocrine Organ-Linking NAFLD and Insulin Resistance

The liver is a dynamic organ that plays critical roles in many physiological processes, including the regulation of systemic glucose and lipid metabolism. Dysfunctional hepatic lipid metabolism is a cause of nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disorder worldwide, and is closely associated with insulin resistance and type 2 diabetes. Through the use of advanced mass spectrometry "omics" approaches and detailed experimentation in cells, mice, and humans, we now understand that the liver secretes a wide array of proteins, metabolites, and noncoding RNAs (miRNAs) and that many of these secreted factors exert powerful effects on metabolic processes both in the liver and in peripheral tissues. In this review, we summarize the rapidly evolving field of "hepatokine" biology with a particular focus on delineating previously unappreciated communication between the liver and other tissues in the body. We describe the NAFLD-induced changes in secretion of liver proteins, lipids, other metabolites, and miRNAs, and how these molecules alter metabolism in liver, muscle, adipose tissue, and pancreas to induce insulin resistance. We also synthesize the limited information that indicates that extracellular vesicles, and in particular exosomes, may be an important mechanism for intertissue communication in normal physiology and in promoting metabolic dysregulation in NAFLD.

Overexpression of Hepassocin in Diabetic Patients with Nonalcoholic Fatty Liver Disease May Facilitate Increased Hepatic Lipid Accumulation

Methods:

The study enrolled 60 patients plus 20 healthy controls that were divided into 4 groups: Group I: included 20 patients who were diagnosed as diabetes mellitus type 2, Group II: included 20 patients who were diagnosed as nonalcoholic fatty liver disease (NAFLD), Group III: included 20 patients who were diagnosed as diabetes type 2 and NAFLD, and Group IV (control group): included 20 healthy person or controls who were matched in age and sex with patients group. All patients and controls were subjected to full history taking, thorough clinical examination, laboratory investigations including measurement of serum hepassocin in peripheral blood by ELISA technique.

Results:

There was a significant overexpression of serum hepassocin in patients with type 2 diabetes and NAFLD patients (Group 3) more than diabetic patients (Group 1) and even more than non-alcoholic fatty liver disease (Group 2).

Conclusion:

This study provides evidence that increased HPS may facilitate increased hepatic lipid accumulation with NAFLD and type 2 diabetes.

Obesity Drives STAT-1-Dependent NASH and STAT-3-Dependent HCC

Obesity is a major driver of cancer, especially hepatocellular carcinoma (HCC). The prevailing view is that non-alcoholic steatohepatitis (NASH) and fibrosis or cirrhosis are required for HCC in obesity. Here, we report that NASH and fibrosis and HCC in obesity can be dissociated. We show that the oxidative hepatic environment in obesity inactivates the STAT-1 and STAT-3 phosphatase T cell protein tyrosine phosphatase (TCPTP) and increases STAT-1 and STAT-3 signaling. TCPTP deletion in hepatocytes promoted T cell recruitment and ensuing NASH and fibrosis as well as HCC in obese C57BL/6 mice that normally do not develop NASH and fibrosis or HCC. Attenuating the enhanced STAT-1 signaling prevented T cell recruitment and NASH and fibrosis but did not prevent HCC. By contrast, correcting STAT-3 signaling prevented HCC without affecting NASH and fibrosis. TCPTP-deletion in hepatocytes also markedly accelerated HCC in mice treated with a chemical carcinogen that promotes HCC without NASH and fibrosis. Our studies reveal how obesity-associated hepatic oxidative stress can independently contribute to the pathogenesis of NASH, fibrosis, and HCC.

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Obesity promotes hepatic STAT-1 and STAT-3 signaling

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Obesity promotes STAT-1-dependent T cell-infiltration, NASH, and fibrosis

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Obesity promotes NASH-independent STAT-3-dependent HCC

Hyperlipidemia-induced hepassocin in the liver contributes to insulin resistance in skeletal muscle

Hepassocin (HPS) has recently been identified as a novel hepatokine that causes hepatic steatosis. However, the role of HPS in the development of insulin resistance in skeletal muscle under obesity remains unclear. The effect of hyperlipidemia on hepatic HPS expression was evaluated in primary hepatocytes and liver of mice. HPS-mediated signal pathways were explored using small interfering (si) RNAs of specific genes or inhibitors. We found that treatment of primary hepatocytes with palmitate could induce HPS expression through C/EBPβ-mediated transcriptional activation. Furthermore, increased HPS expression was observed in the liver of high fat diet (HFD)-fed or tunicamycin-treated mice. Pretreatment with 4-phenylbutyrate (4-BPA) (an endoplasmic reticulum (ER) stress inhibitor) and suppression of p38 by siRNA abrogated the effect of palmitate on HPS expression in primary hepatocytes. Treatment of differentiated C2C12 cells with recombinant HPS caused c-Jun N-terminal kinase (JNK) phosphorylation and impairment of insulin sensitivity in a dose-dependent manner. siRNA-mediated suppression of JNK reduced the effect of HPS on insulin signaling. Furthermore, the suppression of epidermal growth factor receptor (EGFR) by siRNA mitigated both HPS-induced JNK phosphorylation and insulin resistance. In addition, HPS did not affect inflammation and ER stress in differentiated C2C12 cells. In conclusion, we elucidated that ER stress induced by palmitate could increase the expression of HPS in hepatocytes and further contribute to the development of insulin resistance in skeletal muscle via EGFR/JNK-mediated pathway. Taken together, we suggest that HPS could be a therapeutic target for obesity-linked insulin resistance.

The Hepatic Protection Effects of Hepassocin in Hyperglycemic Crisis

CONTEXT

High glucose generates reactive oxygen species (ROS) and contributes to glucotoxicity in hepatocytes, and hyperglycemia causes structural and functional damage to the liver. However, only a mild hepatic dysfunction was observed in subjects with hyperglycemic crisis, implying a factor exists to exert a hepatic protective effect. Hepassocin is a hepatokine that modulates the proliferation and metabolism of hepatocytes and also exerts protective activity in liver injury. However, its role in hyperglycemic crisis-induced hepatic dysfunction remains unknown.

OBJECTIVE

To investigate the possible hepatic protection effects of hepassocin in hyperglycemic crisis.

DESIGN, SETTING, AND PATIENTS

Plasma hepassocin concentrations and routine biochemistry were measured in 21 patients with hyperglycemic crisis before and after standard treatments. The effects of hepassocin on hepatic functions were evaluated in streptozotocin-induced hyperglycemic mice (STZ mice). HepG2 cells were used to clarify the possible mechanisms regulating hepassocin expression.

RESULTS

Plasma hepassocin concentrations decreased significantly in subjects with hyperglycemic crisis after standard treatment accompanied by improved hepatic functions. Correction of hyperglycemia in STZ mice also decreased the hepatic hepassocin expression. Injection of recombinant hepassocin improved hepatic functions and histologic changes and increased the expression of antioxidative stress proteins, including superoxide dismutase 1 (SOD1). In HepG2 cells, high glucose increased hepassocin expression through signal transducer and activator of transcription 3 and hepatocyte nuclear factor-related pathways. We also demonstrated that hepassocin increased SOD1 expression through an extracellular signal-regulated kinase 1/2 nuclear factor erythroid-2-related factor 2 pathway, decreasing ethyl acetate-induced ROS production and improving cell viability.

CONCLUSIONS

Increased hepassocin secretion in hyperglycemic crisis might offset the deleterious effects of hyperglycemia on hepatocytes.

A novel hepatokine, HFREP1, plays a crucial role in the development of insulin resistance and type 2 diabetes

AIMS/HYPOTHESIS

Type 2 diabetes is highly correlated with nonalcoholic fatty liver disease (NAFLD). Hepatocyte-derived fibrinogen-related protein 1 (HFREP1) is a hepatokine that mediates NAFLD development; however, the role of HFREP1 in the development of insulin resistance and diabetes remains obscure.

METHODS

A total of 193 age- and sex-matched participants with normal glucose tolerance, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and newly diagnosed diabetes (NDD) were recruited for a cross-sectional study. Plasma HFREP1 levels were measured and multivariate linear regression analysis was used to evaluate the relationship between HFREP1, IFG, IGT and NDD. The causal relationship between HFREP1 and insulin resistance was then investigated in animal and cell models. Glucose and insulin tolerance tests, and euglycaemic-hyperinsulinaemic clamp, were used to evaluate insulin sensitivity in animals with Hfrep1 overexpression or knockdown in liver by lentiviral vectors. HepG2 cells were used to clarify the possible mechanism of HFREP1-induced insulin resistance.

RESULTS

Plasma HFREP1 concentrations were significantly increased in participants with IFG, IGT and NDD. HFREP1 concentrations were independently associated with fasting plasma glucose levels, insulin resistance, IFG, IGT and NDD. Injection of recombinant HFREP1 or Hfrep1 overexpression induced insulin resistance in mice, and HFREP1 disrupted insulin signalling to induce insulin resistance through an extracellular signal-regulated kinase (ERK)1/2-dependent pathway. Moreover, hepatic knockdown of HFREP1 improved insulin resistance in both mice fed a high-fat diet and ob/ob mice.

CONCLUSIONS/INTERPRETATION

These findings highlight the crucial role of HFREP1 in insulin resistance and diabetes, and provide a potential strategy and biomarker for developing therapeutic approaches to combat these diseases.

CGRP may regulate bone metabolism through stimulating osteoblast differentiation and inhibiting osteoclast formation

Calcitonin-gene-related peptide (CGRP) is a neuropeptide, which is widely distributed throughout the central and peripheral nervous systems. Numerous mechanisms underlying the action of CGRP in osteoblast-associated cells have been suggested for bone growth and metabolism. The present study was designed to closely investigate the osteoblast‑ and osteoclast-associated mechanisms of the effect of CGRP administration on bone metabolism in primary osteoblasts. Primary osteoblasts were obtained from newborn rabbit calvaria and incubated with different concentrations of human CGRP (hCGRP), hCGRP and hCGRP (8‑37), or without treatment as a control. Intracellular calcium (Ca2+) and cyclic adenosine monophosphate (cAMP) were detected following treatment, as well as the expression levels of osteoblast differentiation markers, including activating transcription factor‑4 (ATF4) and osteocalcin (OC), and receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG). The isolated primary osteoblasts were found to stain positively for ALP. hCGRP treatment had no significant effect on transient intracellular Ca2+ in the osteoblasts. Treatment of the osteoblasts with hCGRP led to elevations in the expression levels of cAMP, ATF4 and OPG, and downregulation in the expression of RANKL, in a dose‑dependent manner. These effects were markedly reversed by the addition of hCGRP (8‑37). The results of the present study demonstrated that CGRP administration not only stimulated osteoblast differentiation, as demonstrated by upregulated expression levels of ATF4 and OC in the hCGRP‑treated osteoblasts, but also inhibited OPG/RANKL‑regulated osteoclastogenesis. CGRP may act as a modulator of bone metabolism through osteoblast and osteoclast-associated mechanisms, which result in osteoblast formation with subsequent activation of bone formation.

Leveraging a Multi-Omics Strategy for Prioritizing Personalized Candidate Mutation-Driver Genes: A Proof-of-Concept Study

The expression of mutant forms of proteins (e.g., oncogenes and tumor suppressors) has implications in cancer biology and clinical practice. Initial efforts have been made to characterize the transcription of tumor-mutated alleles; however, few studies have been reported to link tumor-mutated alleles to proteomics. We aimed to characterize the transcriptional and translational patterns of tumor-mutated alleles. We performed whole-exome sequencing, RNA-seq, and proteome profiling in a hyper-mutated patient of hepatocellular carcinoma. Using the patient as a model, we show that only a small proportion of tumor-mutated alleles were expressed. In this case, 42% and 3.5% of the tumor-mutated alleles were identified to be transcribed and translated, respectively. Compared with genes with germline variations or without mutations, somatic mutations significantly reduced protein expression abundance. Using the transcriptional and translational patterns of tumor-mutated alleles, we classified the mutations into four types, and only one type may be associated with the liver cancer and lead to hepatocarcinogenesis in the patient. Our results demonstrate how tumor-mutated alleles are transcribed and translated, and how the expression enables the classification of somatic mutations that cause cancer. Leveraging multiple ‘omics’ datasets provides a new avenue for understanding patient-specific mutations that underlie carcinogenesis.

Targeted disruption of fibrinogen like protein-1 accelerates hepatocellular carcinoma development

Fibrinogen like protein-1 (Fgl1) is a predominantly liver expressed protein that has been implicated as both a hepatoprotectant and a hepatocyte mitogen. Fgl1 expression is decreased in hepatocellular carcinoma (HCC) and its loss correlates with a poorly differentiated phenotype. To better elucidate the role of Fgl1 in hepatocarcinogenesis, we treated mice wild type or null for Fgl1 with diethyl nitrosamine and monitored for incidence of hepatocellular cancer. We find that mice lacking Fgl1 develop HCC at more than twice the rate of wild type mice. We show that hepatocellular cancers from Fgl1 null mice are molecularly distinct from those of the wild type mice. In tumors from Fgl1 null mice there is enhanced activation of Akt and downstream targets of the mammalian target of rapamycin (mTOR). In addition, there is paradoxical up regulation of putative hepatocellular cancer tumor suppressors; tripartite motif-containing protein 35 (Trim35) and tumor necrosis factor super family 10b (Tnfrsf10b). Taken together, these findings suggest that Fgl1 acts as a tumor suppressor in hepatocellular cancer through an Akt dependent mechanism and supports its role as a potential therapeutic target in HCC.

NF-κB signaling relieves negative regulation by miR-194 in hepatocellular carcinoma by suppressing the transcription factor HNF-1α

Constitutive activation of the proinflammatory transcription factor nuclear factor κB (NF-κB) plays an important role in progression of hepatocellular carcinoma (HCC). Emerging modulators of NF-κB signaling are noncoding RNAs, especially microRNAs (miRNAs). We previously identified miRNAs that reduced the induction of NF-κB activity upon addition of tumor necrosis factor-α (TNFα) to HCC cells. We found that among these miRNAs, the abundance of liver-enriched miR-194 was decreased in HCC tissue and that low abundance of miR-194 correlated with a high occurrence of vascular invasion. Overexpressing miR-194 suppressed HCC cell migration and invasiveness in culture and metastatic seeding in mice. Transcripts encoding tripartite motif containing 23 (TRIM23), a ubiquitin ligase involved in NF-κB activation, and chromosome 21 open reading frame 91 (C21ORF91), a protein of unknown function, were identified as direct targets of miR-194 in HCC cells; knocking down either protein decreased the activity of a luciferase NF-κB reporter. Furthermore, the NF-κB pathway activator TNFα, an inflammatory cytokine, inhibited the transcription of miR-194 by decreasing the abundance of hepatocyte nuclear factor-1α (HNF-1α). The abundance of miR-194 positively correlated with that of HNF-1α and inversely correlated with that of TNFα in human HCC tissue. Thus, we identified a pathway in which TNFα-NF-κB signaling switches off negative regulation by suppressing HNF-1α-mediated expression of miR-194, revealing insight into the mechanisms linking inflammatory pathways, miRNA, and HCC metastasis.

Hepassocin is required for hepatic outgrowth during zebrafish hepatogenesis

BACKGROUND & AIMS

Hepassocin (HPS) is a hepatotrophic growth factor that specifically stimulates hepatocyte proliferation and promotes liver regeneration after liver damage. In this paper, zebrafish were used to investigate the role of HPS in liver development.

METHODS AND RESULTS

During zebrafish development, HPS expression is enriched in liver throughout hepatogenesis. Knockdown of HPS using its specific morpholino leads to a smaller liver phenotype. Further results showed that the HPS knockdown has no effect on the expression of the early endoderm marker gata6 and early hepatic marker hhex. In addition, results showed that the smaller-liver phenotype in HPS morphants was caused by suppression of cell proliferation, not induction of cell apoptosis.

CONCLUSIONS

Current findings indicated that HPS is essential to the later stages of development in vertebrate liver organogenesis.

Hepassocin activates the EGFR/ERK cascade and induces proliferation of L02 cells through the Src-dependent pathway

Hepassocin (HPS) is a secreted protein with mitogenic activity on primary hepatocytes and protects hepatocytes from chemically-induced injury. Our previous studies showed that HPS stimulates proliferation of hepatocytes in an ERK pathway-dependent manner. However, the molecular mechanism of HPS-induced activation of the ERK pathway remains unclear. In this study, we found that HPS induced the phosphorylation of the epidermal growth factor receptor (EGFR) in the human L02 hepatocyte cell line, and this event was concomitant with the activation of the non-receptor tyrosine kinase Src. Specific inhibition of EGFR kinase activity by gefitinib or down-regulation of EGFR by specific EGFR siRNAs prevented HPS-induced activation of the ERK pathway and proliferation of L02 cells. Furthermore, inhibition of Src activity significantly blocked HPS-induced activation of the EGFR, which was suggestive of a ligand-independent transactivation mechanism of EGFR itself as well as ERK phosphorylation and proliferation of L02 cells. These results indicate that EGFR plays an important role in the mitogenic signaling induced by HPS in L02 cell lines and may further stimulate research on the role of HPS in hepatocytes within biological processes in human health and disease.

The role of hepassocin in the development of non-alcoholic fatty liver disease

BACKGROUND & AIMS

While non-alcoholic fatty liver disease (NAFLD) is the most common risk factor of chronic liver disease, the mechanisms that initiate its development are obscure. Hepassocin (HPS) is a hepatokine that has been reported to be involved in liver regeneration. In addition to the mitogenic activity of HPS, HPS expression is decreased in patients with hepatoma. However, the role of HPS in NAFLD is still unknown.

METHODS

A total of 393 subjects with (n=194) or without (n=199) NAFLD were enrolled to evaluate the serum HPS concentration. In order to clarify the causal inference between HPS and NAFLD, we used experimental animal and cell models. Hepatic overexpression or silencing of HPS was achieved by lentiviral vector delivery in mice and lipofectamine transfection in HepG2 cells. Lipogenesis related proteins were detected by Western blots. The expression of inflammatory factors was determined by real-time polymerase chain reaction.

RESULTS

Subjects with NAFLD had a higher serum HPS concentration than those without it. Overexpression of HPS increased hepatic lipid accumulation and NAFLD activity scores (NAS), whereas deletion of HPS improved high fat diet-induced hepatic steatosis and decreased NAS in mice. Additionally, oleic acid, a steatogenic reagent, increased HPS expression in hepatocytes. Furthermore, overexpression of HPS in HepG2 cells induced lipid accumulation through an extracellular signal-regulated kinase 1/2 (ERK1/2)-dependent pathway, whereas deletion of HPS decreased oleic acid-induced lipid accumulation.

CONCLUSIONS

The present study provides evidence that HPS plays an important role in NAFLD and induces hepatic lipid accumulation through an ERK1/2-dependent pathway.

Protective effect of mesenchymal stem cell-conditioned medium on hepatic cell apoptosis after acute liver injury

The aim of this study was to investigate the role of Mesenchymal Stem Cell (MSC) conditioned medium (CM(MSC)) on apoptosis of cultured mouse primary hepatocytes after in vivo carbon tetrachloride (CCl4)-induced acute liver injury. The acute liver injury was induced by injecting CCl4 intraperitoneally in C57/BL6 mice. Hepatocytes were isolated by liver perfusion, cultured in a defined medium to maintain their differentiation and characterized by reverse transcriptase polymerase chain reaction (RT-PCR) using the hepatic cell specific genes albumin, hepatocyte nuclear factor 4 (HNF4) and cytokeratin 18 (CK18). CM(MSC) was generated from cultured bone marrow-derived MSCs (BM-MSCs). BM-MSCs were positive for CD73, CD90, CD44 by flow cytometry and able to differentiate into chondrocytes, adipocytes and osteocytes. Apoptosis was evaluated by both annexin V. CM(MSC) were examined by flow cytometry to detect MSC-derived annexin V- and CD54/CD44-positive microparticles (MPs). In the CCl4-CM(MSC) treated hepatocytes, interleukin-6 (IL-6) was increased on the first day of culture compared to control and CCl4 and was followed by upregulation of fibroblast-like-protein (FGL1) expression after 48 hrs. This was associated with a significant decrease of annexin V positive CCl4-CM(MSC) treated hepatocytes at day 3 post plating. Recombinant IL-6 was induced FGL1 expression in hepatocytes derived from CCl4-treated mice suggesting that CM(MSC), which is enriched also in microparticles, attenuates CCl4-induced early apoptosis in hepatocytes through activation of FGL1.

Targeted deletion of fibrinogen like protein 1 reveals a novel role in energy substrate utilization

Fibrinogen like protein 1(Fgl1) is a secreted protein with mitogenic activity on primary hepatocytes. Fgl1 is expressed in the liver and its expression is enhanced following acute liver injury. In animals with acute liver failure, administration of recombinant Fgl1 results in decreased mortality supporting the notion that Fgl1 stimulates hepatocyte proliferation and/or protects hepatocytes from injury. However, because Fgl1 is secreted and detected in the plasma, it is possible that the role of Fgl1 extends far beyond its effect on hepatocytes. In this study, we show that Fgl1 is additionally expressed in brown adipose tissue. We find that signals elaborated following liver injury also enhance the expression of Fgl1 in brown adipose tissue suggesting that there is a cross talk between the injured liver and adipose tissues. To identify extra hepatic effects, we generated Fgl1 deficient mice. These mice exhibit a phenotype suggestive of a global metabolic defect: Fgl1 null mice are heavier than wild type mates, have abnormal plasma lipid profiles, fasting hyperglycemia with enhanced gluconeogenesis and exhibit differences in white and brown adipose tissue morphology when compared to wild types. Because Fgl1 shares structural similarity to Angiopoietin like factors 2, 3, 4 and 6 which regulate lipid metabolism and energy utilization, we postulate that Fgl1 is a member of an emerging group of proteins with key roles in metabolism and liver regeneration.

A cluster of cooperating tumor-suppressor gene candidates in chromosomal deletions

The large chromosomal deletions frequently observed in cancer genomes are often thought to arise as a "two-hit" mechanism in the process of tumor-suppressor gene (TSG) inactivation. Using a murine model system of hepatocellular carcinoma (HCC) and in vivo RNAi, we test an alternative hypothesis, that such deletions can arise from selective pressure to attenuate the activity of multiple genes. By targeting the mouse orthologs of genes frequently deleted on human 8p22 and adjacent regions, which are lost in approximately half of several other major epithelial cancers, we provide evidence suggesting that multiple genes on chromosome 8p can cooperatively inhibit tumorigenesis in mice, and that their cosuppression can synergistically promote tumor growth. In addition, in human HCC patients, the combined down-regulation of functionally validated 8p TSGs is associated with poor survival, in contrast to the down-regulation of any individual gene. Our data imply that large cancer-associated deletions can produce phenotypes distinct from those arising through loss of a single TSG, and as such should be considered and studied as distinct mutational events.

Hepassocin regulates cell proliferation of the human hepatic cells L02 and hepatocarcinoma cells through different mechanisms

Hepassocin (HPS) is a specific mitogenic active factor for hepatocytes, and inhibits growth by overexpression in hepatocellular carcinoma (HCC) cells. However, the mechanism of HPS regulation on growth of liver-derived cells still remains largely unknown. In this study, we found that HPS was expressed and secreted into the extracellular medium in cultured L02 human hepatic cells; conditional medium of L02 cells promoted proliferation of L02 cells and this activity could be blocked by anti-HPS antibody. Moreover, we identified the presence of receptor for HPS on L02 cells and HepG2 human hepatoma cells. Overproduction of truncated HPS, which signal peptide was deleted, significantly inhibited the proliferation of HCC cells and induced cell cycle arrest. These findings suggest that HPS promotes hepatic cell line L02 cells proliferation via an autocrine mechanism and inhibits HCC cells proliferation by an intracrine pathway.

Identification of differentially expressed genes in the livers of chronically i-As-treated hamsters

Inorganic arsenic (i-As) is a human carcinogen causing skin, lung, urinary bladder, liver and kidney tumors. Chronic exposure to this naturally occurring contaminant, mainly via drinking water, is a significant worldwide environmental health concern. To explore the molecular mechanisms of arsenic hepatic injury, a differential display polymerase chain reaction (DD-PCR) screening was undertaken to identify genes with distinct expression patterns between the liver of low i-As-exposed and control animals. Golden Syrian hamsters (5-6 weeks of age) received drinking water containing 15 mg i-As/L as sodium arsenite, or unaltered water for 18 weeks. The in vivo MN test was carried out, and the frequency of micronucleated reticulocytes (MN-RETs) was scored as a measure of exposure and As-related genotoxic/carcinogenic risk. A total of 68 differentially expressed bands were identified in our initial screen, 41 of which could be assigned to specific genes. Differential level of expression of a selected number of genes was verified using real-time RT-PCR with gene-specific primers. Arsenic-altered gene expression included genes related to stress response, cellular metabolism, cell cycle regulation, telomere maintenance, cell-cell communication and signal transduction. Significant differences of MN-RET were found between treated (8.70 ± 0.02 MN/1000RETs) and control (2.5 ± 0.70 MN/1000RETs) groups (P<0.001), demonstrating both the exposure and the i-As genotoxic/carcinogenic risk. Overall, this paper reveals some possible networks involved in hepatic arsenic-related genotoxicity, carcinogenesis and diabetogenesis. Additional studies to explore further the potential implications of each candidate gene are of especial interest. The present work opens the door to new prospects for the study of i-As mechanisms taking place in the liver under chronic settings.

Nuclear factor p65 interacts with Keap1 to repress the Nrf2-ARE pathway

Keap1 is an inhibitor of Nrf2 involved in Nrf2-dependent antioxidant response. However, the mechanisms on how Keap1 regulates Nrf2-ARE signaling pathway remains to be determined. Here, by using a yeast two-hybrid technology, p65 subunit of NF-κB transcription factor was identified as a partner of Keap1. We show that Keap1 physically associated with p65 in vivo and in vitro. Overexpression of p65 inhibited Nrf2-dependent transcription induced by diethylmaleate (DEM) or tert-butyl hydroxyquinone (tBHQ). Knock down of Keap1 by RNA interference partially blocked the repression of Nrf2-mediated activation by p65. It was demonstrated that p65 decreased Nrf2 binding to its cognate DNA sequences and enhanced Nrf2 ubiquitination. The N-terminal region of p65 is necessary for both the interaction with Keap1 and its transcriptional suppression activity. Moreover, nuclear translocation of Keap1 was augmented by p65. Taken together, our findings suggest that NF-κB signaling inhibits Nrf2-ARE pathway through the interaction of p65 and Keap1.

miR-194 is a marker of hepatic epithelial cells and suppresses metastasis of liver cancer cells in mice

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression by interacting with the 3' untranslated region (3'-UTR) of multiple mRNAs. Recent studies have linked miRNAs to the development of cancer metastasis. In this study, we show that miR-194 is specifically expressed in the human gastrointestinal tract and kidney. Moreover, miR-194 is highly expressed in hepatic epithelial cells, but not in Kupffer cells or hepatic stellate cells, two types of mesenchymal cells in the liver. miR-194 expression was decreased in hepatocytes cultured in vitro, which had undergone a dedifferentiation process. Furthermore, expression of miR-194 was low in liver mesenchymal-like cancer cell lines. The overexpression of miR-194 in liver mesenchymal-like cancer cells reduced the expression of the mesenchymal cell marker N-cadherin and suppressed invasion and migration of the mesenchymal-like cancer cells both in vitro and in vivo. We further demonstrated that miR-194 targeted the 3'-UTRs of several genes that were involved in epithelial-mesenchymal transition and cancer metastasis.

CONCLUSION

These results support a role of miR-194, which is specifically expressed in liver parenchymal cells, in preventing liver cancer cell metastasis.

Role of cadherin-17 in oncogenesis and potential therapeutic implications in hepatocellular carcinoma

Cadherin is an important cell adhesion molecule that plays paramount roles in organ development and the maintenance of tissue integrity. Dysregulation of cadherin expression is often associated with disease pathology including tissue dysplasia, tumor formation, and metastasis. Cadherin-17 (CDH17), belonging to a subclass of 7D-cadherin superfamily, is present in fetal liver and gastrointestinal tract during embryogenesis, but the gene becomes silenced in healthy adult liver and stomach tissues. It functions as a peptide transporter and a cell adhesion molecule to maintain tissue integrity in epithelia. However, recent findings from our group and others have reported aberrant expression of CDH17 in major gastrointestinal malignancies including hepatocellular carcinoma (HCC), stomach and colorectal cancers, and its clinical association with tumor metastasis and advanced tumor stages. Furthermore, alternative splice isoforms and genetic polymorphisms of CDH17 gene have been identified in HCC and linked to an increased risk of HCC. CDH17 is an attractive target for HCC therapy. Targeting CDH17 in HCC can inhibit tumor growth and inactivate Wnt signaling pathway in concomitance with activation of tumor suppressor genes. Further investigation on CDH17-mediated oncogenic signaling and cognate molecular mechanisms would shed light on new targeting therapy on HCC and potentially other gastrointestinal malignancies.