Hui-Lu Zhang

Endotoxin accumulation prevents carcinogen‐induced apoptosis and promotes liver tumorigenesis in rodents

Increasing evidence suggests that the presence of endotoxemia is of substantial clinical relevance to patients with cirrhosis, but it is unclear whether and how gut‐derived LPS amplifies the tumorigenic response of the liver. We found that the circulating levels of LPS were elevated in animal models of carcinogen‐induced hepatocarcinogenesis. Reduction of LPS using antibiotics regimen in rats or genetic ablation of its receptor Toll‐like receptor 4 (TLR4) in mice prevented excessive tumor growth and multiplicity. Additional investigation revealed that TLR4 ablation sensitizes the liver to carcinogen‐induced toxicity via blocking NF‐κB activation and sensitizing the liver to reactive oxygen species (ROS)‐induced toxicity, but lessens inflammation‐mediated compensatory proliferation. Reconstitution of TLR4‐expressing myeloid cells in TLR4‐deficient mice restored diethylnitrosamine (DEN)‐induced hepatic inflammation and proliferation, indicating a paracrine mechanism of LPS in tumor promotion. Meanwhile, deletion of gut‐derived endotoxin suppressed DEN‐induced cytokine production and compensatory proliferation, whereas in vivo LPS pre‐challenge promotes hepatocyte proliferation. Conclusion: Our data indicate that sustained LPS accumulation represents a pathological mediator of inflammation‐associated hepatocellular carcinoma (HCC) and manipulation of the gut flora to prevent pathogenic bacterial translocation and endotoxin absorption may favorably influence liver function in patients with cirrhosis who are at risk of developing HCC. (Hepatology 2010.)

Hepatitis B virus X (HBx) induces tumorigenicity of hepatic progenitor cells in 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine‐treated HBx transgenic mice

Hepatitis B virus X (HBx) protein is implicated in hepatitis B virus (HBV)‐associated liver carcinogenesis. However, it remains unclear whether HBx‐expressing hepatic progenitor cells (HPCs) are attributed to liver tumor formation. In this study, by using HBx transgenic mice and a 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine (DDC)‐induced liver injury model, the relationship between HBx expression and tumorigenicity of HPCs was analyzed. Compared with control mice, an elevated number of EpCAM+ cells with characteristics of HPCs was observed in HBx mice after 1 month and 4 months of DDC diet feeding. All HBx transgenic mice developed liver tumors characterized by histological features of both hepatocellular carcinoma (HCC) and cholangiocarcinoma after 7 months of DDC feeding. Notably, EpCAM+ HPCs isolated from premalignant HBx mice exposed to a DDC diet for 4 months formed subcutaneous mixed‐lineage tumors (four out of six) in nonobese diabetic/severe‐combined immunodeficient (NOD/SCID) mice, and none of the cells from wildtype (WT) induced tumor, indicating that HBx may induce malignant transformation of HPCs that contributes to tumorigenesis. We also found higher titers of circulating interleukin (IL)‐6, activities of IL‐6/STAT3, and Wnt/β‐catenin signaling pathways in HBx transgenic mice, suggesting HBx may induce intrinsic changes in HPCs by way of the above signaling that enables HPCs with tumorigenicity potential. Finally, clinical evidence showed that high HBx expression in human HBV‐related HCC was statistically associated with expansion of EpCAM+ or OV6+ tumor cells and aggressive clinicopathologic features. Conclusion: HBx induces intrinsic cellular transformation promoting the expansion and tumorigenicity of HPCs in DDC‐treated mice, which may be a possible origin for liver cancer induced by chronic hepatitis infection. (HEPATOLOGY 2012)

Profound impact of gut homeostasis on chemically-induced pro-tumorigenic inflammation and hepatocarcinogenesis in rats

BACKGROUND & AIMS Due to its anatomic connection, the liver is constantly exposed to gut-derived bacterial products or metabolites. Disruption of gut homeostasis is associated with many human diseases. The aim of this study was to determine the role of gut homeostasis in initiation and progression of hepatocellular carcinoma (HCC). METHODS Disruption of intestinal homeostasis by penicillin or dextran sulfate sodium (DSS) and its restoration by probiotics were applied in a diethylnitrosamine (DEN) model of rat hepatocarcinogenesis. RESULTS Patients with liver cirrhosis and HCC had significantly increased serum endotoxin levels. Chronic DEN treatment of rats was associated with an imbalance of subpopulations of the gut microflora including a significant suppression of Lactobacillus species, Bifidobacterium species and Enterococcus species as well as intestinal inflammation. Induction of enteric dysbacteriosis or intestinal inflammation by penicillin or DSS, respectively, significantly promoted tumor formation. Administration of probiotics dramatically mitigated enteric dysbacteriosis, ameliorated intestinal inflammation, and most importantly, decreased liver tumor growth and multiplicity. Interestingly, probiotics not only inhibited the translocation of endotoxin, which bears pathogen-associated molecular patterns (PAMPs) but also the activation of damage-associated molecular patterns (DAMPs) such as high-mobility group box 1 (HMGB1). As a result, the production of pro- and anti-inflammatory cytokines was skewed in favor of a reduced tumorigenic inflammation in the liver. CONCLUSIONS The data highlights the importance of gut homeostasis in the pathogenesis of HCC. Modulation of the gut microbiota by probiotics may represent a new avenue for therapeutic intervention to treat or prevent HCC development.

OV6 + tumor-initiating cells contribute to tumor progression and invasion in human hepatocellular carcinoma

BACKGROUND & AIMS Accumulating evidence suggests the involvement of tumor-initiating cells (T-ICs) in cancer genesis, but whether liver T-ICs contribute to HCC invasion and metastasis remains unclear. METHODS OV6(+) T-ICs were isolated from SMMC7721 and HuH7 cell lines by magnetic sorting. Characteristics of T-ICs were assessed by in vitro and mouse xenograft assays. Expression of OV6 was determined by immunostaining in specimens from 218 HCC patients, and Kaplan-Meier survival analysis was used to determine the correlation of OV6 expression with prognosis. RESULTS OV6(+) T-ICs isolated from HCC cell lines not only possess a higher capacity to form tumor spheroids in vitro, but also had a greater potential to form tumors when implanted in non-obese diabetic/severe combined immunodeficient mice, suggesting their elevated self-renewal capacity and tumorigenicity. Moreover, OV6(+) T-ICs exhibited more invasive and metastatic potentials both in vitro and in vivo. Patients with more OV6(+) tumor cells were associated with aggressive clinicopathologic features and poor prognosis. CXCR4 is expressed at higher levels in OV6(+) cells. Recombinant stromal cell-derived factor-1 (SDF-1) treatment expanded the OV6(+) HCC T-ICs population, by sustaining the stem cell property of OV6(+) cells. The SDF-1 effect was blocked by a specific CXCR4 inhibitor, AMD3100, or transfection of siRNA targeting CXCR4. CONCLUSIONS OV6(+) HCC cells may represent a subpopulation of T-ICs with augmented invasion and metastasis potential, which contribute to progression and metastasis of HCC. The SDF-1/CXCR4 axis also provides therapeutic targets for elimination of liver T-ICs.

p53 promotes inflammation-associated hepatocarcinogenesis by inducing HMGB1 release

BACKGROUND & AIMS Hepatocellular carcinoma (HCC) develops in response to chronic hepatic injury. Although induced cell death is regarded as the major component of p53 tumor-suppressive activity, we recently found that sustained p53 activation subsequent to DNA damage promotes inflammation-associated hepatocarcinogenesis. Here we aim at exploring the mechanism linking p53 activation and hepatic inflammation during hepatocarcinogenesis. METHODS p53(-/-) hepatocytes expressing inducible p53 and primary wild type hepatocytes were treated to induce p53 expression. The supernatants were collected and analyzed for the presence of released inflammatory cytokines. Ethyl pyruvate was used in a rat model of carcinogen-induced hepatocarcinogenesis to examine its effect on p53-dependent chronic hepatic injury, inflammation, and tumorigenesis. RESULTS Here we show that cytoplasmic translocation and circulating levels of potent inflammatory molecule high-mobility group protein 1 (HMGB1) were greater in wild type rats than in p53(+/-) rats following carcinogen administration. Restoration of p53 expression in p53-null hepatocytes or induction of endogenous p53 in wild type hepatocytes gives rise to the release of HMGB1. Administration of the HMGB1 release inhibitor ethyl pyruvate, which does not affect p53-mediated hepatic apoptosis, substantially prevented carcinogen-induced cirrhosis and tumorigenesis in rat livers. CONCLUSIONS These results suggest that although p53 is usually regarded as a tumor suppressor, its constant activation can promote pro-tumorigenic inflammation, at least in part, via inducing HMGB1 release. Application of HMGB1 inhibitors when restoring p53 in cancer therapy might protect against pro-tumorigenic effects while leaving p53-mediated clearance of malignant cells intact.

Acetyl‐coenzyme A carboxylase alpha promotion of glucose‐mediated fatty acid synthesis enhances survival of hepatocellular carcinoma in mice and patients

Solid tumors often suffer from suboptimal oxygen and nutrient supplies. This stress underlies the requirement for metabolic adaptation. Aberrantly activated de novo lipogenesis is critical for development and progression of human hepatocellular carcinoma (HCC). However, whether de novo lipogenesis influences biological behaviors of HCCs under conditions of metabolic stress are still poorly understood. Here, we show that HCCs display distinct levels of glucose‐derived de novo lipogenesis, which are positively correlated with their survival responses to glucose limitation. The enhanced lipogenesis in HCCs is characterized by an increased expression of rate‐limiting enzyme acetyl‐coenzyme A carboxylase alpha (ACCα). ACCα‐mediated fatty acid (FA) synthesis determines the intracellular lipid content that is required to maintain energy hemostasis and inhibit cell death by means of FA oxidation (FAO) during metabolic stress. In accord, overexpression of ACCα facilitates tumor growth. ACCα forms a complex with carnitine palmitoyltransferase 1A (CPT1A) and prevents its mitochondria distribution under nutrient‐sufficient conditions. During metabolic stress, phosphorylation of ACCα leads to dissociation of the complex and mitochondria localization of CPT1A, thus promoting FAO‐mediated cell survival. Therefore, ACCα could provide both the substrate and enzyme storage for FAO during glucose deficiency. Up‐regulation of ACCα is also significantly correlated with poorer overall survival and disease recurrence postsurgery. Multivariate Coxs regression analysis identified ACCα as an effective predictor of poor prognosis. Conclusion: These results present novel mechanistic insight into a pivotal role of ACCα in maintaining HCC survival under metabolic stress. It could be exploited as a novel diagnostic marker and therapeutic target. (Hepatology 2016;63:1272–1286)

Gut-Derived Lipopolysaccharide Promotes T-Cell–Mediated Hepatitis in Mice through Toll-Like Receptor 4

Robust clinical and epidemiologic data support the role of inflammation as a key player in hepatocellular carcinoma (HCC) development. Our previous data showed that gut-derived lipopolysaccharide (LPS) promote HCC development by activating Toll-like receptor 4 (TLR4) expressed on myeloid-derived cells. However, the effects of gut-derived LPS on other types of liver injury models are yet to be studied. The purpose of this study was to determine the importance of gut-derived LPS and TLR4 signaling in a T-cell–mediated hepatitis—Con A–induced hepatitis model, which mimic the viral hepatitis. Reduction of endotoxin using antibiotics regimen or genetic ablation of TLR4 in mice significantly alleviate Con A–induced liver injury by inhibiting the infiltration of T lymphocytes into the liver and the activation of CD4+ T lymphocytes as well as the production of T helper 1 cytokines; in contrast, exogenous LPS can promote Con A–induced hepatitis and CD4+ T cells activation in vivo and in vitro. Reconstitution of TLR4–expressing myeloid cells in TLR4-deficient mice restored Con A–induced liver injury and inflammation, indicating the major cell target of LPS. In addition, TLR4 may positively regulate the target hepatocellular apoptosis via the perforin/granzyme B pathway. These data suggest that gut-derived LPS and TLR4 play important positive roles in Con A–induced hepatitis and modulation of the gut microbiotia may represent a new avenue for therapeutic intervention to treat acute hepatitis induced by hepatitis virus infection, thus to prevent hepatocellular carcinoma. Cancer Prev Res; 5(9); 1090–102. ©2012 AACR.

Interleukin-1β/Iinterleukin-1 receptor-associated kinase 1 inflammatory signaling contributes to persistent Gankyrin activation during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a prototype of inflammation‐associated cancer. Oncoprotein Gankyrin, which mostly increases in HCC, plays a critical role in HCC development and metastasis. However, the exact mechanism of Gankyrin up‐regulation in HCC remains unclear. A Gankyrin luciferase reporter was developed to screen a potential regulator for Gankyrin from a list of proinflammatory cytokines, and interleukin (IL)‐1β was found as one of its activators. In clinical premalignant and malignant liver disease samples, enhanced IL‐1β/interleukin‐1 receptor‐associated kinase 1 (IRAK‐1) signaling accompanied by increased Gankyrin was observed. Lower expression of Gankyrin and phospho‐IRAK‐1 are favorable prognostic markers for HCC. A similar correlation was observed in the diethylnitrosamine (DEN) model of rat hepatocarcinogenesis. The results from Gankyrin reporter activity, real‐time polymerase chain reaction, or immunoblotting further confirmed the up‐regulation of Gankyrin by IL‐1β/IRAK‐1 inflammatory signaling. Moreover, a series of Gankyrins truncated reporters were constructed, and electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) were performed to analyze the properties of Gankyrin promoter. Mechanistically, the core promoter of Gankyrin contains the binding site of nuclear factor Y (NF‐Y) family members, which can recruit histone acetyltransferase coactivator E1A‐binding protein p300 (p300) or CREB‐binding protein (CBP) to promote Gankyrin transcription. Conversely, knockdown of NF‐Y, p300, or CBP inhibits Gankyrin expression. IL‐1β stimulation causes sequential phosphorylation of IRAK‐1, c‐Jun N‐terminal kinase (JNK), and p300 and enhances recruitment of the p300/CBP/NF‐Y complex to Gankyrin promoter. Inhibition of phospho‐JNK impairs IL‐1β/IRAK‐1 signaling‐mediated up‐regulation of Gankyrin. Conclusion: The finding of IL‐1β/IRAK‐1 signaling promoting Gankyrin expression through JNK and NF‐Y/p300/CBP complex provides a fresh view on inflammation‐enhanced hepatocarcinogenesis. (Hepatology 2015;61:585‐597)

Disturbance of Ca2+ Homeostasis Converts Pro-Met into Non-canonical Tyrosine Kinase p190MetNC in Response to Endoplasmic Reticulum Stress in MHCC97 Cells

Background: Both ER stress and c-Met are implicated in the tumorigenesis of HCC. Results: ER calcium disturbance-induced p190MetNC expression inhibits ER stress-mediated apoptosis. Conclusion: p190MetNC, but not p190Metαβ, plays a critical role in promoting HCC cells survival under ER stress. Significance: We identify a novel biochemical mechanism by which c-Met ensures HCC cell survival under stress conditions. c-Met, the tyrosine-kinase receptor for hepatocyte growth factor, plays a critical role in the tumorigenesis of hepatocellular carcinoma (HCC). However, the underlying mechanism remains incompletely understood. The mature c-Met protein p190Metαβ (consists of a α subunit and a β subunit) is processed from pro-Met. Here we show that pro-Met is processed into p190MetNC by sarco/endoplasmic reticulum calcium-ATPase (SERCA) inhibitor thapsigargin. p190MetNC compensates for the degradation of p190Metαβ and protects human HCC cells from apoptosis mediated by endoplasmic reticulum (ER) stress. In comparison with p190Metαβ, p190MetNC is not cleaved and is expressed as a single-chain polypeptide. Thapsigargin-initiated p190MetNC expression depends on the disturbance of ER calcium homeostasis. Once induced, p190MetNC is activated independent of hepatocyte growth factor engagement. p190MetNC contributes to sustained high basal activation of c-Met downstream pathways during ER calcium disturbance-mediated ER stress. Both p38 MAPK-promoted glucose-regulated protein 78 (GRP78) expression and sustained high basal activation of PI3K/Akt and MEK/ERK are involved in the cytoprotective function of p190MetNC. Importantly, the expression of p190MetNC is detected in some HCC cases. Taken together, these data provide a potential mechanism to explain how c-Met promotes HCC cells survival in response to ER stress. We propose that context-specific processing of c-Met protein is implicated in HCC progression in stressful microenvironments.

Aldehyde dehydrogenase‐2 (ALDH2) opposes hepatocellular carcinoma progression by regulating AMP‐activated protein kinase signaling in mice

Potential biomarkers that can be used to determine prognosis and perform targeted therapies are urgently needed to treat patients with hepatocellular carcinoma (HCC). To meet this need, we performed a screen to identify functional genes associated with hepatocellular carcinogenesis and its progression at the transcriptome and proteome levels. We identified aldehyde dedydrogenase‐2 (ALDH2) as a gene of interest for further study. ALDH2 levels were significantly lower at the mRNA and protein level in tumor tissues than in normal tissues, and they were even lower in tissues that exhibited increased migratory capacity. A study of clinical associations showed that ALDH2 is correlated with survival and multiple migration‐associated clinicopathological traits, including the presence of metastasis and portal vein tumor thrombus. The result of overexpressing or knocking down ALDH2 showed that this gene inhibited migration and invasion both in vivo and in vitro. We also found that ALDH2 altered the redox status of cells by regulating acetaldehyde levels and that it further activated the AMP‐activated protein kinase (AMPK) signaling pathway. Conclusion: Decreased levels of ALDH2 may indicate a poor prognosis in HCC patients, while forcing the expression of ALDH2 in HCC cells inhibited their aggressive behavior in vitro and in mice largely by modulating the activity of the ALDH2‐acetaldehyde‐redox‐AMPK axis. Therefore, identifying ALDH2 expression levels in HCC might be a useful strategy for classifying HCC patients and for developing potential therapeutic strategies that specifically target metastatic HCC. (Hepatology 2017;65:1628‐1644).