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The SOCS1 gene coding for suppressor of cytokine signaling 1 is frequently repressed in hepatocellular carcinoma (HCC), and hence SOCS1 is considered a tumor suppressor in the liver. However, the tumor-suppressor mechanisms of SOCS1 are not yet well understood. SOCS1 is known to inhibit pro-inflammatory cytokine production and signaling and to promote activation of the p53 tumor suppressor. However, we observed that SOCS1-deficient mice developed numerous and large liver tumor nodules following treatment with the hepatocarcinogen diethylnitrosamine (DEN) without showing increased interleukin-6 production or activation of p53. On the other hand, the livers of DEN-treated Socs1-null mice showed elevated levels of p21(CIP1/WAF1) protein (p21). Even though p21 generally functions as a tumor suppressor, paradoxically many cancers, including HCC, are known to express elevated levels of p21 that correlate with poor prognosis. We observed elevated p21 expression also in the regenerating livers of SOCS1-deficient mice and in cisplatin-treated Socs1-null hepatocytes, wherein the p21 protein showed increased stability. We show that SOCS1 interacts with p21 and promotes its ubiquitination and proteasomal degradation. Besides, the DEN-treated livers of Socs1-null mice showed increased nuclear and cytosolic p21 staining, and the latter was associated with growth factor-induced, phosphatidylinositol 3-kinase-dependent phosphorylation of p21 in SOCS1-deficient hepatocytes. Cytosolic p21 is often associated with malignancy and chemo-resistance in many cancers. Accordingly, SOCS1-deficient hepatocytes showed increased resistance to apoptosis that was reversed by shRNA-mediated p21 knockdown. In the regenerating livers of Socs1-null mice, increased p21 expression coincided with elevated cyclinD levels. Correspondingly, SOCS1-deficient hepatocytes showed increased proliferation to growth factor stimulation that was reversed by p21 knockdown. Overall, our findings indicate that the tumor-suppressor functions of SOCS1 in the liver could be mediated, at least partly, via regulation of the expression, stability and subcellular distribution of p21 and its paradoxical oncogenic functions, namely, resistance to apoptosis and increased proliferation.

Suppressor of cytokine signaling 1 (SOCS1) is considered as a tumor suppressor protein in hepatocellular carcinoma (HCC), but the underlying mechanisms remain unclear. Previously, we have shown that SOCS1-deficient hepatocytes displayed increased responsiveness to hepatocyte growth factor (HGF) due to enhanced signaling via the MET receptor tyrosine kinase. As aberrant MET activation occurs in many tumors including HCC, here we elucidated the mechanisms of SOCS1-mediated regulation. SOCS1 attenuated HGF-induced proliferation of human and mouse HCC cell lines and their growth as tumors in NOD.scid.gamma mice. Tumors formed by SOCS1 expressing HCC cells showed significantly reduced MET expression, indicating that SOCS1 not only attenuates MET signaling but also regulates MET expression. Mechanistically, SOCS1 interacted with MET via the Src homology 2 domain and this interaction was promoted by MET tyrosine kinase activity. The SOCS1-mediated reduction in MET expression does not require the juxtamembrane Y1003 residue implicated in Cbl-mediated downmodulation. Moreover, the proteasome inhibitor MG-132, but not the inhibitors of lysosomal degradation bafilomycin and chloroquine, reversed the SOCS1-mediated reduction in MET expression, indicating that this process is distinct from Cbl-mediated downmodulation. Accordingly, SOCS1 promoted polyubiquitination of MET via K48-dependent but not K63-mediated ubiquitin chain elongation. Furthermore, siRNA-mediated downmodulation of Cbl did not abolish SOCS1-mediated reduction in MET expression in HCC cells. SOCS1-dependent ubiquitination of endogenous MET receptor occurred rapidly following HGF stimulation in HCC cells, leading to proteasomal degradation of phosphorylated MET receptor. These findings indicate that SOCS1 mediates its tumor suppressor functions, at least partly, by binding to MET and interfering with downstream signaling pathways as well as by promoting the turnover of the activated MET receptor. We propose that loss of this control mechanism due to epigenetic repression of SOCS1 could contribute to oncogenic MET signaling in HCC and other cancers, and that MET inhibitors might be useful in treating these patients.

Background and Aims: SH2 domain-containing protein tyrosine phosphatase 2 (Shp2) is the first identified pro-oncogenic tyrosine phosphatase that acts downstream of receptor tyrosine kinases (RTKs) to promote Ras-extracellular signal-regulated kinase signaling. However, this phosphatase was also shown to be antitumorigenic in HCC. This study is aimed at deciphering paradoxical Shp2 functions and mechanisms in hepatocarcinogenesis and at exploring its value as a pharmaceutical target in HCC therapy., Approaches and Results: We took both genetic and pharmaceutical approaches to examine the effects of Shp2 inhibition on primary liver cancers driven by various oncogenes and on metastasized liver tumors. We show here that the catalytic activity of Shp2 was essential for relay of oncogenic signals from RTKs in HCC and that chemical inhibition of Shp2 robustly suppressed HCC driven by RTKs. However, in contrast to a tumor-promoting hepatic niche generated by genetically deleting Shp2 in hepatocytes, treatment with a specific Shp2 inhibitor had a tumor-suppressing effect on metastasized liver tumor progression. Mechanistically, the Shp2 inhibitor enhanced antitumor innate immunity by down-regulating inflammatory cytokines, suppressing the chemokine (C-C motif) receptor 5 signaling axis, but up-regulating interferon-β secretion., Conclusions: These results unveil complex mechanisms for the tumor-suppressing effect of pharmaceutical Shp2 inhibition in the liver immune environment. We provide a proof of principle for clinical trials with specific Shp2 inhibitors in patients with primary and metastasized liver cancer., (Copyright © 2023 American Association for the Study of Liver Diseases.)

The SOCS1 gene is a frequent target of epigenetic repression in hepatocellular carcinoma. Many other types of cancer also harbor methylated SOCS1 gene. Besides, recent studies implicate microRNAs targeting SOCS1 in cancer progression. These findings suggest a broad tumor suppressor role of SOCS1 and have stimulated the quest to elucidate the underlying molecular mechanisms. The essential physiological function of SOCS1 is to attenuate interferon gamma signaling in immune cells. SOCS1 binds activated JAK kinases and the receptor chains of several cytokines, some of which are implicated in cancer progression. SOCS1 also facilitates ubiquitination and proteasomal degradation of many signaling molecules downstream of cytokine and growth factor receptors. We have shown that SOCS1 inhibits signaling via the hepatocyte growth factor receptor c-MET in hepatocytes. Aberrant MET signaling, implicated in the progression of many types of cancers, also contributes to the development of chemoresistance to tyrosine kinase inhibitors and drugs targeting other oncogenic signaling pathways. Here, we discuss the SOCS1-dependent regulation of MET signaling as an important mechanism underlying the tumor suppressor role of SOCS1 that is relevant not only to hepatocellular carcinoma but also to other types of cancers.

Hepatocellular carcinoma (HCC) remains a significant disease worldwide and its incidence is expected to increase. In selected patients, liver transplantation offers a 5-year patient survival between 48% and 75%. However, HCC recurrence occurs in approximately 20% of transplant recipients. No therapy has proven efficacious in decreasing the risk of recurrence after transplantation. Sorafenib, a multitargeted tyrosine kinase inhibitor, has been shown to improve survival in patients with advanced HCC that have no history of liver transplantation. We report complete remission of HCC in a 54-year-old man who developed biopsy-proven lung metastasis after liver transplantation treated with sorafenib.

Hepatitis B virus (HBV) reinfection and recurrence of hepatocellular carcinoma (HCC) after orthotopic liver transplantation (OLT) are associated with increased graft failure and reduced patient survival. We evaluated the effects of both HCC recurrence and HBV reinfection on the long-term survival of these patients after OLT. One hundred seventy-five patients underwent OLT for HBV-related liver diseases and were the subjects of this retrospective study. We assessed risk factors for HBV reinfection, HCC recurrence, and survival post-OLT using univariate and multivariate analyses. During a mean follow-up of 43.0 +/- 42.0 months, 88 of 175 (50.3%) patients transplanted for HBV-related liver disease had HCC prior to OLT. Thirteen (14.8%) of these patients had HCC recurrence after OLT. The mean time for recurrence of HCC was 26.1 +/- 31.9 months. Twelve of 175 (6.9%) patients developed HBV reinfection after liver transplantation. The mean time for HBV reinfection was 28.7 +/- 26.4 months. Ten of these 12 (83.3%) patients had HCC prior to OLT, and 5 (50%) developed recurrence of HCC. On multivariate analyses, pre-OLT HCC and recurrence of HCC post-OLT were significantly associated with HBV reinfection after transplantation (P = 0.031 and P < 0.001, respectively). HCC recurrence after OLT was associated with lymphovascular invasion (P < 0.001) and post-OLT chemotherapy (P < or = 0.001). The 3- and 5-year survival rates were significantly decreased in patients with HBV reinfection (P = 0.007) and in patients with HCC recurrence after OLT (P = 0.03). In conclusion, pre-OLT HCC and HCC recurrence after transplantation were associated with HBV reinfection and with decreased patient survival. Hepatitis B immunoglobulin and antiviral therapy was only partially effective in preventing HBV reinfection in patients with HCC recurrence.

Background: Prophylaxis of HBV recurrence is critical after liver transplantation in HBV patients. Despite new prophylactic schemes, most European LT centres persist on a conservative approach combining hepatitis B immunoglobulin (HBIG) and nucleos(t)ides analogues (NA)., Aim: This setting prompted the European Liver Intestine Transplantation Association (ELITA) to look for a consensus on the prevention of HBV recurrence., Methods: Based on a 4-round Delphi process, ELITA investigated 16 research questions and established 50 recommendations., Results: Prophylaxis should be driven according to 3 simplified risk groups: Low and high virological risk patients, with undetectable and detectable HBV DNA pre-LT, respectively, and special populations (HDV, HCC, poorly adherent patients). In low-risk patients, short-term (4 weeks) combination of third-generation NA+ HBIG, or third generation NA monotherapy can be considered as prophylactic options. In high-risk patients, HBIG can be discontinued once HBV DNA undetectable. Combined therapy for 1 year is advised. HBV-HCC patients should be treated according to their virological risk. In HDV/HBV patients, indefinite dual prophylaxis remains the gold standard. Full withdrawal of HBV prophylaxis following or not HBV vaccination should only be attempted in the setting of clinical trials. Organs from HBsAg+ve donors may be considered after assessment of risks, benefits, and patient consent. They should not be used if HDV is present. In poorly adherent patients, dual long-term prophylaxis is recommended. Budget impact analysis should be taken into account to drive prophylactic regimen., Conclusions: These ELITA recommendations should stimulate a more rational and homogeneous approach to HBV prophylaxis across LT programs., (© 2021 John Wiley & Sons Ltd.)

Background and Aims: Trimethylation of Lys36 on histone 3 (H3K36me3) catalyzed by histone methyltransferase SET domain-containing 2 (SETD2) is one of the most conserved epigenetic marks from yeast to mammals. SETD2 is frequently mutated in multiple cancers and acts as a tumor suppressor., Approach and Results: Here, using a liver-specific Setd2 depletion model, we found that Setd2 deficiency is sufficient to trigger spontaneous HCC. Meanwhile, Setd2 depletion significantly increased tumor and tumor size of a diethylnitrosamine-induced HCC model. The mechanistic study showed that Setd2 suppresses HCC not only through modulating DNA damage response, but also by regulating lipid metabolism in the liver. Setd2 deficiency down-regulated H3K36me3 enrichment and expression of cholesterol efflux genes and caused lipid accumulation. High-fat diet enhanced lipid accumulation and promoted the development of HCC in Setd2-deficient mice. Chromatin immunoprecipitation sequencing analysis further revealed that Setd2 depletion induced c-Jun/activator protein 1 (AP-1) activation in the liver, which was trigged by accumulated lipid. c-Jun acts as an oncogene in HCC and functions through inhibiting p53 in Setd2-deficient cells., Conclusions: We revealed the roles of Setd2 in HCC and the underlying mechanisms in regulating cholesterol homeostasis and c-Jun/AP-1 signaling., (© 2020 by the American Association for the Study of Liver Diseases.)

Antiviral therapy has been shown to improve the prognosis of hepatitis B virus (HBV) DNA-positive hepatocellular carcinoma (HCC) after radical treatment, but antiviral treatments require further optimization. This study aimed to evaluate the efficacies of different antiviral strategies with HCC patients after hepatectomy/ablation. This prospective, randomized, controlled and multi-centre trial enrolled HBV DNA-positive primary HCC patients after hepatectomy/ablation between January 2007 and January 2009. Patients were divided into four groups: early combination (entecavir plus Peg-interferon [IFN]α-2a co-administration during year 1); late combination (addition of Peg-IFNα-2a for 48 weeks after 1 year of entecavir); nucleos(t)ide analogue[NA] monotherapy; and non-antiviral treatment. Primary endpoints included recurrence-free survival and overall survival. A total of 447 patients were enrolled. The 2-year and 8-year recurrence-free survival and 8-year overall survival rates were significantly higher in the early combination group than in the other two antiviral groups (P < .05). After 48-week treatment, more patients achieved an HBsAg reduction >1500 IU/mL and the mean HBsAg level was significantly lower in the early combination group compared with the late combination and NA monotherapy groups (P < .05). Multivariate analysis showed that early combination therapy and a reduction in HBsAg by >1500 IU/mL after 48 weeks of therapy correlated with reduced mortality and disease recurrence. Early introduction of combination antiviral treatment may represent a more effective therapeutic strategy for patients with HBV DNA-positive HCC after hepatectomy/ablation. A reduction in HBsAg by >1500 IU/mL after 48-week treatment is associated with reduced mortality and disease recurrence of HBV DNA-positive HCC patients after hepatectomy/ablation., (© 2019 John Wiley & Sons Ltd.)

Plenty of evidence has suggested that long noncoding RNAs (lncRNAs) play a vital role in competing endogenous RNA (ceRNA) networks. Poorly differentiated hepatocellular carcinoma (PDHCC) is a malignant phenotype. This paper aimed to explore the effect and the underlying regulatory mechanism of lncRNAs on PDHCC as a kind of ceRNA. Additionally, prognosis prediction was assessed. A total of 943 messenger RNAs (mRNAs), 86 miRNAs, and 468 lncRNAs that were differentially expressed between 137 PDHCCs and 235 well-differentiated HCCs were identified. Thereafter, a ceRNA network related to the dysregulated lncRNAs was established according to bioinformatic analysis and included 29 lncRNAs, 9 miRNAs, and 96 mRNAs. RNA-related overall survival (OS) curves were determined using the Kaplan-Meier method. The lncRNA ARHGEF7-AS2 was markedly correlated with OS in HCC (P = .041). Moreover, Cox regression analysis revealed that patients with low ARHGEF7-AS2 expression were associated with notably shorter survival time (P = .038). In addition, the area under the curve values of the lncRNA signature for 1-, 3-, and 5-year survival were 0.806, 0.741, and 0.701, respectively. Furthermore, a lncRNA nomogram was established, and the C-index of the internal validation was 0.717. In vitro experiments were performed to demonstrate that silencing ARHGEF7-AS2 expression significantly promoted HCC cell proliferation and migration. Taken together, our findings shed more light on the ceRNA network related to lncRNAs in PDHCC, and ARHGEF7-AS2 may be used as an independent biomarker to predict the prognosis of HCC., (© 2019 Wiley Periodicals, Inc.)