Transformation Of Liver Cells Research Articles

Aldose reductase interacts with AKT1 to augment hepatic AKT/mTOR signaling and promote hepatocarcinogenesis.

Marked up-regulation of aldose reductase (AR) is reportedly associated with the development of hepatocellular carcinoma (HCC). We investigated how aberrantly overexpressed AR might promote oncogenic transformation in liver cells and tissues. We found that overexpressed AR interacted with the kinase domain of AKT1 to increase AKT/mTOR signaling. In both cultured liver cancer cells and liver tissues in DEN-induced transgenic HCC model mice, we observed that AR overexpression-induced AKT/mTOR signaling tended to enhance lactate formation and hepatic inflammation to enhance hepatocarcinogenesis. Conversely, AR knockdown suppressed lactate formation and inflammation. Using cultured liver cancer cells, we also demonstrated that AKT1 was essential for AR-induced dysregulation of AKT/mTOR signaling, metabolic reprogramming, antioxidant defense, and inflammatory responses. These findings suggest that aberrantly overexpressed/over-activated hepatic AR promotes HCC development at least in part by interacting with oncogenic AKT1 to augment AKT/mTOR signaling. Inhibition of AR and/or AKT1 might serve as an effective strategy for the prevention and therapy of liver cancer.

Cadmium-induced malignant transformation of rat liver cells: Potential key role and regulatory mechanism of altered apolipoprotein E expression in enhanced invasiveness

Cadmium is a transition metal that is classified as human carcinogen by the International Agency for Research on Cancer (IARC) with multiple target sites. Many studies using various model systems provide evidence of cadmium-induced malignancy formation in vivo or malignant cell transformation in vitro. Nonetheless, further studies are needed to completely understand the mechanisms of cadmium carcinogenicity. Our prior studies have utilized a rat liver epithelial cell line (TRL 1215) as a model for cadmium-induced malignant transformation. In the present study, we focused on the molecular mechanisms of this malignant transformation, especially with regard to hyper-invasiveness stimulated by cadmium transformation. By performing a series of biochemical analyses on cadmium transformed cells, it was determined that cadmium had significantly down-regulated the expression of apolipoprotein E (ApoE). ApoE was recently established as a suppressor of cell invasion. A key factor in the suppression of ApoE by cadmium appeared to be that the metal evoked a 5-aza-2'-deoxycytidine-sensitive hypermethylation of the regulatory region of ApoE, coupled with interference of the action of liver X receptor α (LXRα), a transcriptional regulator for ApoE. Furthermore, the expression of LXRα itself was suppressed by cadmium-mediated epigenetic modification. Re-expression of ApoE clearly abrogated the cell invasion stimulated by cadmium-induced malignant transformation. Together, the current results suggest that the cadmium-mediated enhanced cell invasion is linked to down-regulation of ApoE during malignant transformation these liver cells.

HBx drives alpha fetoprotein expression to promote initiation of liver cancer stem cells through activating PI3K/AKT signal pathway.

Hepatitis B virus (HBV)-X protein (HBx) plays critical role in inducing the malignant transformation of liver cells. Alpha fetoprotein (AFP) expression is closely related to hepatocarcinogenesis. We report that Oct4, Klf4, Sox2 and c-myc expression positively associated with AFP(+)/HBV(+) hepatocellular carcinoma(HCC) tissues, and the expression of the stemness markers CD44, CD133 and EpCAM was significantly higher in AFP(+)/HBV(+) HCC tissues compared to normal liver tissues or AFP (-)/HBV(-) HCC tissues. AFP expression turned on prior to expression of Oct4, Klf4, Sox2 and c-myc, and the stemness markers CD44, CD133 and EpCAM in the normal human liver L-02 cell line or CHL cell lines upon transfection with MCV-HBx vectors. Stem-like cells generated more tumour colonies compared to primary cells, and xenografts induced tumourigenesis in nude mice. Expression of reprogramming-related proteins was significantly enhanced in HLE cells while transfected with pcDNA3.1-afp vectors. The specific PI3K inhibitor Ly294002 inhibited the effects of pcDNA3.1-afp vectors. AFP-siRNA vectors were able to inhibit tumour colony formation and reprogramming-related gene expression. Altogether, HBx stimulates AFP expression to induce natural reprogramming of liver cells, and AFP plays a critical role in promoting the initiation of HCC progenitor/stem cells. AFP may be a potential novel biotarget for combating HBV-induced hepatocarcinogenesis.

Implication of the Hedgehog pathway in hepatocellular carcinoma.

The prognosis for patients who are diagnosed with advanced stage hepatocellular carcinoma (HCC) is poor because there are few treatment options. Recent research has focused on the identification of novel molecular entities that can be targeted to inhibit oncogenic signals that are involved in the carcinogenesis, proliferation and progression of HCC. Among all of the pathways that are involved in the development of HCC, Hedgehog (HH) signalling has demonstrated a substantial role in hepatocarcinogenesis and HCC progression. HH plays a physiological role in embryogenesis, through the induction of the differentiation of hepatocytes from endodermal progenitors. The re-activation of the HH pathway in chronic damaged liver is a mechanism of fibrotic degeneration and is implicated in various stages of HCC development. HH activation sustains the sub-population of immature liver epithelial cells that are involved in the pathogenesis of cirrhosis and HCC, and HH itself is a mediator of the alcohol-derived malignant transformation of liver cells. High levels of expression of HH protein markers in liver tumour tissues are correlated with aggressive histological and biological features and a poor clinical outcome. In vitro and in vivo inhibition models of the HH pathway confirm that HH is essential in maintaining tumour growth, metastasis and a mesenchymal phenotype.

Small heterodimer partner 1 directly interacts with NS5A viral protein and has a key role in HCV related liver cell transformation.

HCV life cycle is strictly correlated with the hepatocyte lipid metabolism; moreover, the progression of HCV chronic hepatitis is accelerated by the presence of liver steatosis. Among the steatogenic genes deregulated during the HCV infection one of the most attractive is the Small Heterodimer Protein 1 (SHP1; NR0B2), that is involved in a remarkable number of metabolic functions. HCV NS5A is an essential and integral component of the HCV membranous-web replicon complex (RC) and plays an essential role to transfer the viral genome from the RCs to the surface of the lipid droplets (LDs) that, in turn, play a key function during HCV life cycle.With the help of a HCV infection model, we demonstrate a functional interaction between SHP1 and HCV NS5A protein. SHP1 silencing (siSHP1) reversed the pro-oncogenic effects of HCV infection, inducing a significant decrease in liver lipid accumulation and in NS5A protein expression. Moreover, siSHP1 causes a strong modulation of some genes involved in HCV-related EMT, such as: HNF4, a central regulators of hepatocyte differentiation, E-Cadherin, SNAILs.Our data suggest that SHP1 results not only to be strictly connected to the pathogenesis of HCV-related liver steatosis, but also to its progression towards the liver transformation.

Nonalcoholic Lipid Accumulation and Hepatocyte Malignant Transformation.

Worldwide incidence of hepatocellular carcinoma (HCC) is steadily increasing, highlighting its status as a public health concern, particularly due to its significant association with other comorbidities, such as diabetes. However, nonalcoholic fatty liver disease (NAFLD) has emerged as a primary risk factor, with its own prevalence increasing in recent years, and it has gradually caught up with the historical primary etiological factors of infection with hepatitis B virus and hepatitis C virus, exposure to aflatoxin, or alcohol liver disease. The deeply worrisome aspects of all of these high risk factors, however, are their remarkable presence within populations. Systemic and genetic mechanisms involved in the malignant transformation of liver cells, as well as useful biomarkers of early stage HCC are being investigated. However, the exact mechanisms underlying the interrelation of NAFLD and HCC remain largely unknown. In this review, some of the recent advances in our understanding of liver lipid accumulation are summarized and discussed to provide insights into the relationship between NAFLD and hepatocyte malignant transformation.

The complex role of NOTCH receptors and their ligands in the development of hepatoblastoma, cholangiocarcinoma and hepatocellular carcinoma.

The NOTCH signalling pathway is one of the key molecular pathways of embryonic development and adult tissues homeostasis in mammals. Mammals have four NOTCH receptors and various ligands that modulate their activity. Many cell disorders, whose genesis involves the NOTCH signalling pathway, have been discovered, including cancer. The mechanisms by which these receptors and their ligands affect liver cell transformation are not yet well understood, and they seem to behave as both oncogenes and tumour-suppressor proteins. In this review, we discuss the published data regarding the role of these proteins in the development of hepatoblastoma, cholangiocarcinoma and hepatocellular carcinoma malignancies. The alteration of the NOTCH signalling pathway may be one of the main drivers of hepatic neoplastic growth. However, this signalling pathway might also modulate the development of specific liver tumour features. The complexity of the function of NOTCH receptors and their ligands may be due to their interactions with many other cell signalling pathways. Furthermore, the different levels of expression and activation of these receptors could be a reason for their distinct and sometimes contradictory effects.

Condurango (Gonolobus condurango) Extract Activates Fas Receptor and Depolarizes Mitochondrial Membrane Potential to Induce ROS-dependent Apoptosis in Cancer Cells in vitro: CE-treatment on HeLa: a ROS-dependent mechanism.

Objectives:Condurango (Gonolobus condurango) extract is used by complementary and alternative medicine (CAM) practitioners as a traditional medicine, including homeopathy, mainly for the treatment of syphilis. Condurango bark extract is also known to reduce tumor volume, but the underlying molecular mechanisms still remain unclear.Methods:Using a cervical cancer cell line (HeLa) as our model, the molecular events behind condurango extract’s (CE’s) anticancer effect were investigated by using flow cytometry, immunoblotting and reverse transcriptase-polymerase chain reaction (RT-PCR). Other included cell types were prostate cancer cells (PC3), transformed liver cells (WRL-68), and peripheral blood mononuclear cells (PBMCs).Results:Condurango extract (CE) was found to be cytotoxic against target cells, and this was significantly deactivated in the presence of N-acetyl cysteine (NAC), a scavenger of reactive oxygen species (ROS), suggesting that its action could be mediated through ROS generation. CE caused an increase in the HeLa cell population containing deoxyribonucleic acid (DNA) damage at the G zero/Growth 1 (G0/G1) stage. Further, CE increased the tumor necrosis factor alpha (TNF-α) and the fas receptor (FasR) levels both at the ribonucleic acid (RNA) and the protein levels, indicating that CE might have a cytotoxic mechanism of action. CE also triggered a sharp decrease in the expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB ) both at the RNA and the protein levels, a possible route to attenuation of B-cell lymphoma 2 (Bcl-2), and caused an opening of the mitochondrial membrane’s permeability transition (MPT) pores, thus enhancing caspase activities.Conclusion:Overall, our results suggest possible pathways for CE mediated cytotoxicity in model cancer cells.

Hepatitis B virus X protein induces expression of alpha-fetoprotein and activates PI3K/mTOR signaling pathway in liver cells.

The hepatitis B virus (HBV)-X protein (HBx) induces malignant transformation of liver cells, and elevated expression of alpha-fetoprotein (AFP) is a significant biomarker of hepatocarcinogenesis. However, the role of AFP in HBV-related hepatocarcinogenesis is unclear. In this study, we investigated the regulatory impact of AFP expression on HBx-mediated malignant transformation of human hepatocytes. We found that HBV induced the expression of AFP before that of oncogenes, e.g., Src, Ras and chemokine (C-X-C motif) receptor 4 (CXCR4), and AFP activated protein kinase B (AKT) and mammalian target of rapamycin (mTOR) in HBV-related HCC tissues and in human liver cells transfected with HBx. Cytoplasmic AFP interacted with and inhibited phosphatase and tensin homolog deleted on chromosome 10 (PTEN), activating the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway and promoting mTOR-mediated stimulation of the transcription factor hypoxia inducible factor-1α (HIF-1α), and therefore led to the activation of the promoters of Src, CXCR4, and Ras genes. On the contrary, reduced expression of AFP by siRNA resulted in the repression of p-mTOR, pAKT, Src, CXCR4, and Ras in human malignant liver cells. Taken together, for the first time our study indicates that HBx-induced AFP expression critically promote malignant transformation in liver cells through the activation of PI3K/mTOR signaling.

HBx induced expression of alpha fetoprotein drives malignant transformation of liver cells

HBx induced expression of alpha fetoprotein drives malignant transformation of liver cells

Transformation of Mouse Liver Cells by Methylcholanthrene Leads to Phenotypic Changes Associated with Epithelial-mesenchymal Transition.

Environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs) have been implicated in cancer development and progression. However, the effects of PAHs on carcinogenesis are still poorly understood. Here, we characterized a mouse cancer cell line BNL 1ME A. 7R.1 (1MEA) derived by transformation of non-tumorigenic liver cell line BNL CL.2 (BNL) using 3-methylcholanthrene (3MC), a carcinogenic PAH. RT-PCR and immunoblot analysis were used to determine the expression level of mRNA and proteins, respectively. To determine functionality, cell motility was assessed in vitro using a transwell migration assay. Both mRNA and protein levels of E-cadherin were significantly decreased in 1MEA cells in comparison with BNL cells. While the expression levels of mesenchymal markers and related transcription factors were enhanced in 1MEA cells, which could lead to increase in cell motility. Indeed, we found that 7-day exposure of BNL cells to 3-MC reduced the level of the adhesion molecule and epithelial marker Ecadherin and increased reciprocally the level of the mesenchymal marker vimentin in a dose-dependent manner. Taken together, these results indicate that the process of epithelial-mesenchymal transition (EMT) may be activated during premalignant transformation induced by 3-MC. A mechanism study to elucidate the relation between 3-MC exposure and EMT is underway in our laboratory.

Correlation between the overexpression of urokinase receptor isoform uPAR (D1D2) and hepatic cell malignant transformation

In order to provide an abundant source of specimen and to reveal the correlation between the overexpression of urokinase plasminogen activator receptor isoform uPAR (D1D2) and hepatic cell malignant transformation, the optimal liver cell culture method was selected from three cell culture methods to culture and separate out liver cells with a high density, high purity and high activity. The specimens were used to culture and assess the uPAR (D1D2) mRNA level in normal liver cells, liver cancer cells and para-carcinoma cells. In the present study, the correlation between the overexpression of uPAR (D1D2) and hepatic cell malignant transformation was discussed. When comparing the tissue block adherent method, liver cell grinding method and pancreatic enzyme digestion method, the liver tissue adherent method was found to be economical, simple and overall the optimal method for liver cell culture. This was used as a reference standard for cell culture. RT-PCR was used to determine isoform uPAR (D1D2) mRNA level in normal liver cells, para-carcinoma cells and liver cancer cells. The comparison of uPAR (D1D2) mRNA levels in normal liver cells, para-carcinoma cells and liver cancer cells, demonstrated that the brightness of the cells clearly increased in normal liver cells, para-carcinoma cells and liver cancer cells. The comparison of the cell grey values of three groups demonstrated a statistically significant difference (P<0.05). The liver tissue adherent method was able to produce liver cells with a high density, high purity and high activity, providing a sufficient source of specimen for our subsequent experiments. The electrophoresis results showed that: uPAR (D1D2) mRNA expression increased from normal liver cells to para-carcinoma cells to liver cancer cells, inferring that uPAR (D1D2) mRNA overexpression may be the result of changes in the conformation of the uPAR isoform. In addition, it is closely associated with abnormal cell signal transduction, which leads to clonal proliferation and abnormal differentiation of liver cells with malignant transformation in liver cells.

High density lipoproteins improve insulin sensitivity in high-fat diet-fed mice by suppressing hepatic inflammation

Obesity-induced liver inflammation can drive insulin resistance. HDL has anti-inflammatory properties, so we hypothesized that low levels of HDL would perpetuate inflammatory responses in the liver and that HDL treatment would suppress liver inflammation and insulin resistance. The aim of this study was to investigate the effects of lipid-free apoAI on hepatic inflammation and insulin resistance in mice. We also investigated apoAI as a component of reconstituted HDLs (rHDLs) in hepatocytes to confirm results we observed in vivo. To test our hypothesis, C57BL/6 mice were fed a high-fat diet (HFD) for 16 weeks and administered either saline or lipid-free apoAI. Injections of lipid-free apoAI twice a week for 2 or 4 weeks with lipid-free apoAI resulted in: i) improved insulin sensitivity associated with decreased systemic and hepatic inflammation; ii) suppression of hepatic mRNA expression for key transcriptional regulators of lipogenic gene expression; and iii) suppression of nuclear factor κB (NF-κB) activation. Human hepatoma HuH-7 cells exposed to rHDLs showed suppressed TNFα-induced NF-κB activation, correlating with decreased NF-κB target gene expression. We conclude that apoAI suppresses liver inflammation in HFD mice and improves insulin resistance via a mechanism that involves a downregulation of NF-κB activation.

Alpha fetoprotein can induce malignant transformation of liver cells and be used as a therapeutic target for hepatocellular carcinoma

Alpha fetoprotein can induce malignant transformation of liver cells and be used as a therapeutic target for hepatocellular carcinoma

Nutrient-dependent phosphorylation channels lipid synthesis to regulate PPARα

Peroxisome proliferator-activated receptor (PPAR)α is a nuclear receptor that coordinates liver metabolism during fasting. Fatty acid synthase (FAS) is an enzyme that stores excess calories as fat during feeding, but it also activates hepatic PPARα by promoting synthesis of an endogenous ligand. Here we show that the mechanism underlying this paradoxical relationship involves the differential regulation of FAS in at least two distinct subcellular pools: cytoplasmic and membrane-associated. In mouse liver and cultured hepatoma cells, the ratio of cytoplasmic to membrane FAS-specific activity was increased with fasting, indicating higher cytoplasmic FAS activity under conditions associated with PPARα activation. This effect was due to a nutrient-dependent and compartment-selective covalent modification of FAS. Cytoplasmic FAS was preferentially phosphorylated during feeding or insulin treatment at Thr-1029 and Thr-1033, which flank a dehydratase domain catalytic residue. Mutating these sites to alanines promoted PPARα target gene expression. Rapamycin-induced inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1), a mediator of the feeding/insulin signal to induce lipogenesis, reduced FAS phosphorylation, increased cytoplasmic FAS enzyme activity, and increased PPARα target gene expression. Rapamycin-mediated induction of the same gene was abrogated with FAS knockdown. These findings suggest that hepatic FAS channels lipid synthesis through specific subcellular compartments that allow differential gene expression based on nutritional status.

Signaling Networks Controlling HCC Onset and Progression: Influence of Microenvironment and Implications for Cancer Gene Therapy

Hepatocarcinogenesis, as other epithelial malignancies, has been proved to be a multistep process that, starting from mutagenic events, allows the transformed liver cell to evolve towards a more aggressive phenotype, characterized by the acquisition of migratory/invasive and stem-cell-like properties. Hepatocellular carcinoma(HCC)can originate from both mature hepatocytes and liver precursor/stem cells. Whatever its origin, a common feature of advanced-stage HCC is the reduction or lack of expression of master genes of epithelial/hepatocyte differentiation, i.e. members of the liver enriched transcription factors(LEFTs)family like HNF4α, and conversely an increased expression of epithelial-to-mesenchymal transition(EMT)master genes, i.e. the transcriptional repressors belonging to the Snail family. Recently, it has emerged as members of these families are capable to directly repress each other and to regulate in opposite manner target genes involved in stemness and in hepatocyte differentiation, thus influencing cell outcome between epithelial/differentiated/poor aggressive and mesenchymal/undifferentiated/aggressive phenotype. Consequently, the restoration of LEFT functions in invasive HCC could represent an important goal for anti-cancer therapies. However, any strategy based on gene transfer needs to take in account the influence of micro-environmental factors in HCC tumor niche, like TGFb, responsible for shifting the described balance in tumor cell towards the acquisition of stem-cell like properties and invasiveness, through Snail/EMT induction and LEFTs downregulation. The presence of this cytokine, indeed, was shown to override both anti-EMT and tumor suppressor activity of the ectopically expressed HNF4α protein. In this review, the rationale to propose implementation of HCC gene therapy will be discussed.

Viral Hepatitis Induces Hepatocellular Cancer: What Can We Learn from Epidemiology Comparing Iran and Worldwide Findings?

ContextSeveral risk factors play the role in the development of hepatocellular carcinoma (HCC) from which chronic hepatitis B and C infections are the most important ones. DNA integration of hepatitis viruses alters the function of critical genes promoting malignant transformation of virus-infected liver cells.Evidence AcquisitionThere are remarkable geographic differences in prevalence of chronic viral hepatitis and incidence of HCC. Middle Eastern countries are characterized by a moderate to high prevalence rate of chronic viral hepatitis in the population. This review discusses about epidemiologic findings of hepatitis B and C infections, and HCC, as well as focuses on Middle East countries, particularly Iran. We provide an overview about risk factors, prevention and treatment, and bring up the role of HCC induced by chronic viral hepatitis.ResultsVaccination against hepatitis B virus (HBV) in the early childhood is highly effective to lower infection rates, substantially. For hepatitis C, adequate hygiene when dealing with human blood and screening programs for blood donors can mainly reduce infection rates. As HCC is strongly associated with chronic viral hepatitis, prevention against the infection is crucial for preventing against HCC too.ConclusionsAlthough prevention and treatment of chronic hepatitis B and C have improved within the last decades even in high-risk countries, effective and sustainable reduction of these infections still needs more actions.

Fructose Protects Murine Hepatocytes from Tumor Necrosis Factor-induced Apoptosis by Modulating JNK Signaling

Fructose-induced hepatic ATP depletion prevents TNF-induced apoptosis, whereas it contrarily enhances CD95-induced hepatocyte apoptosis in vitro and in vivo. By contrast, transformed liver cells are not protected against TNF due to metabolic alterations, allowing selective tumor targeting. We analyzed the molecular mechanisms by which fructose modulates cytokine-induced apoptosis. A release of adenosine after fructose-induced ATP depletion, followed by a cAMP response, was demonstrated. Likewise, cAMP and adenosine mimicked per se the modulation by fructose of CD95- and TNF-induced apoptosis. The effects of fructose on cytokine-induced apoptosis were sensitive to inhibition of protein kinase A. Fructose prevented the pro-apoptotic, sustained phase of TNF-induced JNK signaling and thereby blocked bid-mediated activation of the intrinsic mitochondrial apoptosis pathway in a PKA-dependent manner. We explain the dichotomal effects of fructose on CD95- and TNF-induced cell death by the selective requirement of JNK signaling for the latter. These findings provide a mechanistic rationale for the protection of hepatocytes from TNF-induced cell death by pharmacological doses of fructose.

Forced Activation of β-Catenin Signaling Supports the Transformation of hTERT-Immortalized Human Fetal Hepatocytes

Hepatocarcinogenesis is a multistep process driving the progressive transformation of normal liver cells into highly malignant derivatives. Unlimited proliferation and telomere maintenance have been recognized as prerequisites for the development of liver cancer. Moreover, recent studies identified illegitimate β-catenin signaling as relevant hit in a considerable subset of patients. To further investigate the currently not well-understood malignant evolution driven by telomerase and β-catenin, we monitored cytogenetic and phenotypic alterations in untransformed telomerase-immortalized human fetal hepatocytes following forced activation of β-catenin signaling. As expected, constitutive activation of β-catenin signaling significantly enhanced proliferation with decreasing serum dependence. Previously intact contact inhibition was almost completely eliminated. Interestingly, after several passages in cell culture, immortalized clones with dominant-positive β-catenin signaling acquired additional chromosomal aberrations, in particular translocations, anchorage-independent growth capabilities, and formed tumors in athymic nude mice. In further support for the driving role of β-catenin during hepatocarcinogenesis, improved colony growth in soft agar and accelerated tumor formation was also confirmed in Huh7 cells following stable expression of the constitutively active S33Y β-catenin mutant. Telomerase inhibition showed that short-term expansion of transformed clones was not telomerase dependent. Finally, cancer pathway profiling in derived tumors revealed upregulation of characteristic genes associated with invasion and angiogenesis. In conclusion, illegitimate activation of β-catenin signaling enhances the transformation from immortalization to malignant growth in human fetal hepatocytes. Our data functionally confirm a permissive role for β-catenin signaling in the initial phase of hepatocarcinogenesis.

OL-086 Alpha fetoprotein is an intracellular-essential factor for HBx driving malignant transformation of liver cells

OL-086 Alpha fetoprotein is an intracellular-essential factor for HBx driving malignant transformation of liver cells