GADD45-α expression in cirrhosis and hepatocellular carcinoma: relationship with DNA repair and proliferation

Comparative DNA damage induced by eight nitrosamines in primary human and macaque hepatocytes

N-nitrosamines have been increasingly detected in human drugs, raising serious safety concerns due to their potential mutagenicity and carcinogenicity. In order to expand upon the human data available on these drug impurities, we previously used metabolically competent HepaRG human hepatoma cells to evaluate the genotoxicity of eight small-molecule nitrosamines [N-cyclopentyl-4-nitrosopiperazine (CPNP), N-nitrosodibutylamine (NDBA), N-nitrosodiethylamine (NDEA), N-nitrosodimethylamine (NDMA), N-nitrosodiisopropylamine (NDIPA), N-nitrosoethylisopropylamine (NEIPA), N-nitroso-N-methyl-4-aminobutyric acid (NMBA), and N-nitrosomethylphenylamine (NMPA)]. In this study, we used the comet assay to further investigate the DNA damage induced by the eight nitrosamines in primary human hepatocytes (PHHs) from three individual donors and primary macaque hepatocytes (PMHs) from freshly isolated livers of six rhesus macaques. In addition, expression of genes encoding Phase I and II metabolic enzymes and the activities of the enzymes were compared in PHHs and PMHs, and Western blot was used to analyze protein biomarkers of DNA damage and apoptosis in PMHs. All eight nitrosamines induced significant DNA damage in both PHHs and PMHs; with the exception of NDMA, higher fold increases in % tail DNA were detected in PMHs compared to PHHs. Greater interindividual variability in CYP gene expression, enzyme activities, and DNA damage responses was observed in PHHs compared to PMHs. Benchmark concentration (BMC) modeling analysis showed that PHHs had more conservative BMC50 values than PMHs for most nitrosamines tested. Nonetheless, correlation analysis demonstrated that DNA damage data generated by PMHs and 3D HepaRG spheroids were comparable to those of PHHs. Western blot analysis suggested a potential role for the ethyl group in regulating protein expression in the DNA damage and apoptosis pathways for nitrosamines. Overall, this study provides human-relevant DNA damage responses for the eight nitrosamines and indicates that differences in genotoxic potency between PHHs and PMHs are likely related to CYP enzyme activity.

SPRTN is involved in hepatocellular carcinoma development through the ER stress response

Endoplasmic reticulum (ER) stress, prompted by the accumulation of misfolded or unfolded proteins, triggers the activation of the unfolded protein response (UPR) pathway to restore ER homeostasis. This stress response is implicated in the development of hepatocellular carcinoma (HCC). A biallelic mutation in SPRTN is currently the only known single-gene mutation implicated in the early onset of HCC. However, the exact mechanism linking SPRTN mutations to HCC remains unclear. In our study, we analyzed SPRTN and UPR in 21 human HCC tissue samples using RT-qPCR, immunoblot, and immunohistochemistry. We found alterations in the expression levels of SPRTN and UPR-related genes and proteins in HCC samples. The impact of SPRTN on the ER stress response was assessed in SPRTN-depleted HepG2 cells through RNA sequencing, pull-down assay, comet assay, and mitotic index calculation. We demonstrated that SPRTN interacts with the UPR sensor GRP78. Furthermore, we observed a decrease in SPRTN levels during ER stress, and increased sensitivity to ER stress in SPRTN-depleted cells. These findings suggest an essential role for SPRTN in the ER stress response and provide new insights into HCC pathogenesis. This newly discovered function of SPRTN could significantly enhance our understanding and treatment of HCC.

Polymorphisms within DIO2 and GADD45A genes increase the risk of liver disease progression in chronic hepatitis b carriers

The study enrolled 284 patients with chronic hepatitis B virus infection. Participants included people with mild fibrotic lesions (32.5%), moderate to severe fibrotic lesions (27.5%), cirrhotic lesions (22%), hepatocellular carcinoma (HCC) in 5%, and people with no fibrotic lesions in 13%. Eleven SNPs within DIO2, PPARG, ATF3, AKT, GADD45A, and TBX21 were genotyped by mass spectrometry. The rs225014 TT (DIO2) and rs10865710 CC (PPARG) genotypes were independently associated with susceptibility to advanced liver fibrosis. However, cirrhosis was more prevalent in individuals with the GADD45A rs532446 TT and ATF3 rs11119982 TT genotypes. In addition, the rs225014 CC variant of DIO2 was more frequently found in patients with a diagnosis of HCC. These findings suggest that the above SNPs may play a role in HBV-induced liver damage in a Caucasian population.

Impact of growth hormone-releasing hormone (GHRH) antagonist on Decidual stromal cell growth and apoptosis in vitro

Endometrial stromal cells remodeling is critical during human pregnancy. GHRH and its functional receptor have been shown to be expressed in gynecological cancer cells and eutopic endometrial stromal cells. Recent studies have demonstrated the potential clinical uses of antagonists of GHRH as effective antitumor agents because of its directly antagonistic effect on the locally produced GHRH in gynecological tumors. However, the impact of GHRH antagonists on normal endometrial stromal cell growth remained to be elucidated. The aim of this study was to investigate the effect of a GHRH antagonist (JMR-132) on cell proliferation and apoptosis of human decidual stromal cells and the underlying molecular mechanisms. Our results showed that GHRH and the splice variant 1 (SV1) of GHRH receptor (GHRH-R SV1) are expressed in human decidual stromal cells isolated from the decidual tissues of early pregnant women receiving surgical abortion. In addition, treatment of stroma cells with JMR-132 induced cell apoptosis with increasing cleaved caspase-3 and caspase-9 activities, and decrease cell viability in a time- and dose-dependent manner. Using a dual inhibition approach (pharmacological inhibitors and siRNA-mediated knockdown), we showed that JMR-132-induced activation of apoptotic signals are mediated by the activation of ERK1/2 and JNK signaling pathways and the subsequent upregulation of GADD45α. Taken together, JMR-132 suppresses cell survival of decidual stromal cells by inducing apoptosis through the activation of ERK1/2- and JNK-mediated upregulation of GADD45α in human endometrial stromal cells. Our findings provide new insights into the potential impact of GHRH antagonist on the decidual programming in humans.

Comparative analysis of the expression profiles of genes related to the Gadd45α signaling pathway in four kinds of liver diseases

Gadd45α (growth arrest and DNA damage inducible alpha) is a member of a group of genes whose transcript levels are increased following stressful conditions that lead to growth arrest and treatment with agents that lead to DNA damage. Gadd45α is upregulated in liver cirrhosis (LC), hepatic cancer (HC), acute liver failure (AHF) and non-alcoholic fatty liver disease(NAFLD). Here, we investigated the essential differences in the Gadd45α signaling pathway in these diseases at the transcriptional level. The results showed that 44, 46, 71 and 27 genes significant changes in these diseases, and the H-cluster showed that the expression of the Gadd45α signaling-related genes was significantly different in the four liver diseases. DAVID functional analysis showed that the Gadd45α signaling pathway-related genes were mainly involved in cell adhesion and migration, cell proliferation, apoptosis, stress and inflammatory responses, etc. Ingenuity pathway analysis (IPA) software was used to predict the functions of the Gadd45α signaling-related genes, and the results indicated that there were significant changes in cell differentiation, DNA damage repair, autophagy, apoptosis and necrosis. Gadd45α signaling pathway is involved in four kinds of liver disease and regulates a variety of activities via P38 MAPK, NF-κB, mTOR/STAT3, P21, PCNA, PI3K/Akt and other signaling pathways. Modulation of Gadd45α may be exploited to prevent the progression of liver disease, and to identify specific treatments for different stages of liver disease. In summary, the Gadd45α signaling pathway is involved in four kinds of liver disease and regulates a variety of physiological activities through various signaling pathways.

ER Stress Induces Cell Cycle Arrest at the G2/M Phase Through eIF2α Phosphorylation and GADD45α

Endoplasmic reticulum (ER) stress is known to influence various cellular functions, including cell cycle progression. Although it is well known how ER stress inhibits cell cycle progression at the G1 phase, the molecular mechanism underlying how ER stress induces G2/M cell cycle arrest remains largely unknown. In this study, we found that ER stress and subsequent induction of the UPR led to cell cycle arrest at the G2/M phase by reducing the amount of cyclin B1. Pharmacological inhibition of the IRE1α or ATF6α signaling did not affect ER stress-induced cell cycle arrest at the G2/M phase. However, when the alpha subunit of eukaryotic translation initiation factor 2 (eIF2α) phosphorylation was genetically abrogated, the cell cycle progressed without arresting at the G2/M phase after ER stress. GEO database analysis showed that growth arrest and DNA-damage-inducible protein α (Gadd45α) were induced in an eIF2a phosphorylation-dependent manner, which was confirmed in this study. Knockdown of GADD45α abrogated cell cycle arrest at the G2/M phase upon ER stress. Finally, the cell death caused by ER stress significantly reduced when GADD45α expression was knocked down. In conclusion, GADD45α is a key mediator of ER stress-induced growth arrest via regulation of the G2/M transition and cell death through the eIF2α signaling pathway.

Upregulation of UBE2Q1 via gene copy number gain in hepatocellular carcinoma promotes cancer progression through β-catenin-EGFR-PI3K-Akt-mTOR signaling pathway

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and represents a highly malignant tumor with a poor prognosis. Therapeutic modalities for HCC are limited and generally ineffective. UBE2Q1 is a putative E2 ubiquitin conjugating enzyme, and has been shown to be overexpressed in various types of cancers including HCC. How UBE2Q1 contributes to hepatocarcinogenesis remains unknown. Here, we show that UBE2Q1 is up-regulated in HCC cell lines and in a subset of human HCC tissues. Up-regulation of UBE2Q1 in primary HCC tumors was significantly correlated with shorter overall survival and disease-free survival. Mechanistically, we showed that the frequent up-regulation of UBE2Q1 in HCCs was attributed to the recurrent UBE2Q1 gene copy gain at chromosome 1q21. Functionally, we showed that knockdown of UBE2Q1 reduced HCC cell proliferation, promoted apoptosis via induction of GADD45α, and suppressed orthotopic tumorigenicity both in vitro and in vivo. Inactivation of UBE2Q1 also impeded HCC cell migration and invasion in vitro through regulating EMT process, and suppressed HCC metastasis in vivo. Interestingly, our data revealed a role of UBE2Q1 in the regulation of β-catenin-EGFR-PI3K-Akt-mTOR signaling pathway. Our findings indicate that UBE2Q1 is a candidate oncogene involved in HCC development and progression and therefore a potential therapeutic target in applicable HCC patients.

Involvement of hepatic macrophages in the antifibrotic effect of IGF-I-overexpressing mesenchymal stromal cells

BACKGROUND

Cirrhosis is a major health problem worldwide and new therapies are needed. Hepatic macrophages (hMø) have a pivotal role in liver fibrosis, being able to act in both its promotion and its resolution. It is well-known that mesenchymal stromal cells (MSCs) can modulate the immune/inflammatory cells. However, the effects of MSCs over hMø in the context of liver fibrosis remain unclear. We previously described evidence of the antifibrotic effects of in vivo applying MSCs, which were enhanced by forced overexpression of insulin-like growth factor 1 (AdIGF-I-MSCs). The aim of this work was to analyze the effect of MSCs on hMø behavior in the context of liver fibrosis resolution.

METHODS

Fibrosis was induced in BALB/c mice by chronic administration of thioacetamide (8 weeks). In vivo gene expression analyses, in vitro experiments using hMø isolated from the nonparenchymal liver cells fraction, and in vivo experiments with depletion of Mø were performed.

RESULTS

One day after treatment, hMø from fibrotic livers of MSCs-treated animals showed reduced pro-inflammatory and pro-fibrogenic gene expression profiles. These shifts were more pronounced in AdIGF-I-MSCs condition. This group showed a significant upregulation in the expression of arginase-1 and a higher downregulation of iNOS expression thus suggesting decreased levels of oxidative stress. An upregulation in IGF-I and HGF expression was observed in hMø from AdIGF-I-MSCs-treated mice suggesting a restorative phenotype in these cells. Factors secreted by hMø, preconditioned with MSCs supernatant, caused a reduction in the expression levels of hepatic stellate cells pro-fibrogenic and activation markers. Interestingly, hMø depletion abrogated the therapeutic effect achieved with AdIGF-I-MSCs therapy. Expression profile analyses for cell cycle markers were performed on fibrotic livers after treatment with AdIGF-I-MSCs and showed a significant regulation in genes related to DNA synthesis and repair quality control, cell cycle progression, and DNA damage/cellular stress compatible with early induction of pro-regenerative and hepatoprotective mechanisms. Moreover, depletion of hMø abrogated such effects on the expression of the most highly regulated genes.

CONCLUSIONS

Our results indicate that AdIGF-I-MSCs are able to induce a pro-fibrotic to resolutive phenotype shift on hepatic macrophages, which is a key early event driving liver fibrosis amelioration.

Hepatitis C Virus Increases Free Fatty Acids Absorption and Promotes its Replication Via Down-Regulating GADD45α Expression

BACKGROUND Hepatitis C virus (HCV) infection, as a major cause of chronic hepatic diseases, is always accompanied with an abnormality of lipid metabolism. The aim of this study was to investigate the pathogenic role of free fatty acids (FFA) in human HCV infection. MATERIAL AND METHODS Peripheral blood lipid indexes among HCV patients with different viral loads (199 samples) and healthy donors (80 samples) were detected by clinical biochemistry tests. HCV replication and the expression of growth arrest and DNA-damage-inducible gene 45-α (GADD45α) in Huh7 cells and clinical samples were quantified by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. Lipid accumulation in Huh7 cells was detected by immunofluorescence. RESULTS In this study, we found that FFA showed a significant positive correlation with viral load in peripheral blood of HCV patients, but not total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), or low-density lipoprotein cholesterol (LDL-C). GADD45α expression in HCV patients dramatically decreased with the increase of viral load. In Huh7 cells, FFA treatment significantly enhanced HCV replication. HCV infection inhibited GADD45α expression, and this effect was further enhanced with the presence of FFA treatment. Ectopic expression of GADD45α in HCV-infected Huh7 cells markedly inhibited the absorption of FFA and HCV replication. However, FFA significantly elevated GADD45α expression without HCV infection. CONCLUSIONS These results demonstrated that HCV down-regulates GADD45α expression to enhance FFA absorption and thus facilitate its replication. GADD45α is an essential mediator for the pathogenesis of HCV infection. Thus, our study provides potential clues in the search for novel therapeutics and fatty lipid control options for HCV patients.

Akbu-LAAO exhibits potent anti-tumor activity to HepG2 cells partially through produced H2O2 via TGF-β signal pathway

Previously, we characterized the biological properties of Akbu-LAAO, a novel L-amino acid oxidase from Agkistrodon blomhoffii ussurensis snake venom (SV). Current work investigated its in vitro anti-tumor activity and underlying mechanism on HepG2 cells. Akbu-LAAO inhibited HepG2 growth time and dose-dependently with an IC50 of ~38.82 μg/mL. It could induce the apoptosis of HepG2 cells. Akbu-LAAO exhibited cytotoxicity by inhibiting growth and inducing apoptosis of HepG2 as it showed no effect on its cell cycle. The inhibition of Akbu-LAAO to HepG2 growth partially relied on enzymatic-released H2O2 as catalase only partially antagonized this effect. cDNA microarray results indicated TGF-β signaling pathway was linked to the cytotoxicity of Akbu-LAAO on HepG2. TGF-β pathway related molecules CYR61, p53, GDF15, TOB1, BTG2, BMP2, BMP6, SMAD9, JUN, JUNB, LOX, CCND1, CDK6, GADD45A, CDKN1A were deregulated in HepG2 following Akbu-LAAO stimulation. The presence of catalase only slightly restored the mRNA changes induced by Akbu-LAAO for differentially expressed genes. Meanwhile, LDN-193189, a TGF-β pathway inhibitor reduced Akbu-LAAO cytotoxicity on HepG2. Collectively, we reported, for the first time, SV-LAAO showed anti-tumor cell activity via TGF-β pathway. It provides new insight of SV-LAAO exhibiting anti-tumor effect via a novel signaling pathway.

Alpha fetoprotein mediates HBx induced carcinogenesis in the hepatocyte cytoplasm

Although tumor-associated fetal protein AFP has demonstrated utility as a clinical tumor marker, the significance of intracellular AFP is still unclear. The aim of this study was to explore the role of cytoplasmic AFP during HBx induced carcinogenesis, which had not previously been recognized; 614 HCC patients were analyzed for correlation of HBV infection with AFP level, and much higher AFP levels were found in HBsAg positive patients. Tumor tissue specimens from 20 HCC patients were used for analysis of AFP and GADD45α. Analysis of HCC specimens showed that upregulation of cytoplasmic AFP is associated with down-regulation of GADD45α in neoplastic tissue. Transfected HBx promotes transcription of AFP by acting on the elements in the AFP gene regulatory region. HBx itself did not directly impact transcription of GADD45α. However, the obstruction of RAR signaling by HBx induced elevation of AFP, which led to down-regulation of GADD45α. Cytoplasmic AFP was able to interact with RAR, disrupting its entrance into the nucleus and binding to the elements in the regulatory region of the GADD45α gene. Knockdown of AFP in siRNA-transfected AFP positive cell lines was synchronously associated with an incremental increase of RAR binding to DNA, as well as upregulation of GADD45α and it was contrary in AFP gene-transfected AFP negative cell lines. These results indicate cytoplasmic AFP is not only a histochemical tumor biomarker for human hepatoma but is also an intracellular signal molecule and potential participant in HBx induced hepatocarcinogenesis.

p53 controls hepatitis C virus non-structural protein 5A-mediated downregulation of GADD45α expression via the NF-κB and PI3K-Akt pathways

Growth arrest and DNA-damage-inducible gene 45-α (GADD45α) protein has been shown to be a tumour suppressor and is implicated in cell-cycle arrest and suppression of cell growth. The hepatitis C virus (HCV) non-structural 5A (NS5A) protein plays an important role in cell survival and is linked to the development of hepatocellular carcinoma (HCC). However, the role of HCV NS5A in the development of HCC remains to be clarified. This study sought to determine whether GADD45α mediates HCV NS5A-induced cellular survival and to elucidate the molecular mechanism of GADD45α expression regulated by HCV NS5A. It was found that HCV NS5A downregulated GADD45α expression at the transcriptional level by decreasing promoter activity, mRNA transcription and protein levels. Knockdown of p53 resulted in a similar decrease in GADD45α expression to that caused by HCV NS5A, whilst overexpression of p53 reversed the HCV NS5A-mediated downregulation of GADD45α. HCV NS5A repressed p53 expression, which was followed by a subsequent decrease in GADD45α expression. Further evidence was provided showing that HCV NS5A led to increases of phosphorylated nuclear factor-κB and Akt levels. Inhibition of these pathways using pharmacological inhibitors or specific small interfering RNAs rescued HCV NS5A-mediated downregulation of p53 and GADD45α. It was also found that HCV NS5A protein and depletion of GADD45α increased cell growth, whereas ectopic expression of GADD45α eliminated HCV NS5A-induced cell proliferation. These results indicated that HCV NS5A downregulates GADD45α expression and subsequently triggers cellular proliferation. These findings provide new insights suggesting that HCV NS5A could contribute to the occurrence of HCV-related HCC.

Hepatic ontogeny and tissue distribution of mRNAs of epigenetic modifiers in mice using RNA-sequencing

Developmental regulation of gene expression is controlled by distinct epigenetic signatures catalyzed by various epigenetic modifiers. Little is known about the ontogeny and tissue distribution of these epigenetic modifiers. In the present study, we used a novel approach of RNA-sequencing to elucidate hepatic ontogeny and tissue distribution of mRNA expression of 142 epigenetic modifiers, including enzymes involved in DNA methylation/demethylation, histone acetylation/deacetylation, histone methylation/demethylation, histone phosphorylation and chromosome remodeling factors in male C57BL/6 mice. Livers from male C57BL/6 mice were collected at 12 ages from prenatal to adulthood. Many of these epigenetic modifiers were expressed at much higher levels in perinatal livers than adult livers, such as Dnmt1, Dnmt3a, Dnmt3b, Apobec3, Kat1, Ncoa4, Setd8, Ash2l, Dot1l, Cbx1, Cbx3, Cbx5, Cbx6, Ezh2, Suz12, Eed, Suv39h1, Suv420h2, Dek, Hdac1, Hdac2, Hdac7, Kdm2b, Kdm5c, Kdm7, Prmt1-5, Prmt7, Smarca4, Smarcb1, Chd4 and Ino80e. In contrast, hepatic mRNA expression of a few epigenetic modifiers increased during postnatal liver development, such as Smarca2, Kdm1b, Cbx7 and Chd3. In adult mice (60 d of age), most epigenetic modifiers were expressed at moderately (1-3-fold) higher levels in kidney and/or small intestine than liver. In conclusion, this study, for the first time, unveils developmental changes in mRNA abundance of all major known epigenetic modifiers in mouse liver. These data suggest that ontogenic changes in mRNA expression of epigenetic modifiers may play important roles in determining the addition and/or removal of corresponding epigenetic signatures during liver development.

GADD45 proteins: central players in tumorigenesis

The Growth Arrest and DNA Damage-inducible 45 (GADD45) proteins have been implicated in regulation of many cellular functions including DNA repair, cell cycle control, senescence and genotoxic stress. However, the pro-apoptotic activities have also positioned GADD45 as an essential player in oncogenesis. Emerging functional evidence implies that GADD45 proteins serve as tumor suppressors in response to diverse stimuli, connecting multiple cell signaling modules. Defects in the GADD45 pathway can be related to the initiation and progression of malignancies. Moreover, induction of GADD45 expression is an essential step for mediating anti-cancer activity of multiple chemotherapeutic drugs and the absence of GADD45 might abrogate their effects in cancer cells. In this review, we present a comprehensive discussion of the functions of GADD45 proteins, linking their regulation to effectors of cell cycle arrest, DNA repair and apoptosis. The ramifications regarding their roles as essential and central players in tumor growth suppression are also examined. We also extensively review recent literature to clarify how different chemotherapeutic drugs induce GADD45 gene expression and how its up-regulation and interaction with different molecular partners may benefit cancer chemotherapy and facilitate novel drug discovery.

NER factors are recruited to active promoters and facilitate chromatin modification for transcription in the absence of exogenous genotoxic attack

Upon gene activation, we found that RNA polymerase II transcription machinery assembles sequentially with the nucleotide excision repair (NER) factors at the promoter. This recruitment occurs in absence of exogenous genotoxic attack, is sensitive to transcription inhibitors, and depends on the XPC protein. The presence of these repair proteins at the promoter of activated genes is necessary in order to achieve optimal DNA demethylation and histone posttranslational modifications (H3K4/H3K9 methylation, H3K9/14 acetylation) and thus efficient RNA synthesis. Deficiencies in some NER factors impede the recruitment of others and affect nuclear receptor transactivation. Our data suggest that there is a functional difference between the presence of the NER factors at the promoters (which requires XPC) and the NER factors at the distal regions of the gene (which requires CSB). While the latter may be a repair function, the former is a function with respect to transcription unveiled in the current study.

Gonadotropin-releasing hormone type II induces apoptosis of human endometrial cancer cells by activating GADD45alpha

Gonadotropin-releasing hormone type II (GnRH-II) has an antiproliferative effect on human endometrial cancer cells. Apoptosis in cancer cells may play a critical role in regulating cell proliferation. However, more studies are necessary to elucidate the underlying molecular mechanisms and develop potential applications of GnRH-II. Therefore, we explored the mechanisms of GnRH-II-induced apoptosis and the effects of GnRH-II on GADD45alpha activation in human endometrial cancer cell lines. GnRH-II decreased cell viability in a dose- and time-dependent manner. Apoptosis was induced with increased terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling apoptotic cells after GnRH-II treatment. Knockdown of the endogenous GnRH-I receptor with small interfering RNA (siRNA) rescued the cells from GnRH-II-mediated cell growth inhibition and abolished the induction of apoptosis. GnRH-II activated extracellular signal-regulated kinase (ERK)-1/2 and p38 mitogen-activated protein kinase (MAPK) in a time-dependent manner, and the activation was abolished by GnRH-I receptor siRNA and MAPK inhibitors. Cells pretreated with MAPK inhibitors were rescued from GnRH-II-mediated cell growth inhibition. Moreover, both inhibitors abolished GnRH-II-induced apoptosis. GnRH-II induced GADD45alpha expression, which was abolished by knockdown of endogenous GnRH-I receptors and MAPK inhibitors. GnRH-II-stimulated cell growth inhibition was rescued by knockdown of endogenous GADD45alpha with siRNA. Cells treated with GADD45alpha siRNA were refractory to GnRH-II-induced apoptosis. Thus, GnRH-II inhibits cell growth by inducing apoptosis through binding of the GnRH-I receptor, activation of the ERK1/2 and p38 MAPK pathways, and induction of GADD45alpha signaling. This finding may provide a new concept relating to the mechanism of GnRH-II-induced antiproliferation and apoptosis in endometrial cancer cells, indicating the possibility of GnRH-II as a promising therapeutic intervention for human endometrial cancer.

Androgen receptor is a new potential therapeutic target for the treatment of hepatocellular carcinoma

BACKGROUND & AIMS

Androgen effects on hepatocellular carcinoma (HCC) remain controversial and androgen ablation therapy to treat HCC also leads to inconsistent results. Here we examine androgen receptor (AR) roles in hepatocarcinogenesis using mice lacking AR in hepatocytes.

METHODS

By using the Cre-Lox conditional knockout mice model injected with carcinogen, we examined the AR roles in hepatocarcinogenesis. We also tested the possible roles of AR in cellular oxidative stress and DNA damage sensing/repairing systems. By using AR degrading compound, ASC-J9, or AR-small interference RNA, we also examined the therapeutic potentials of targeting AR in HCC.

RESULTS

We found AR expression was increased in human HCC compared with normal livers. We also found mice lacking hepatic AR developed later and less HCC than their wild-type littermates with comparable serum testosterone in both male and female mice. Addition of functional AR in human HCC cells also resulted in the promotion of cell growth in the absence or presence of 5alpha-dihydrotestosterone. Mechanistic dissection suggests that AR may promote hepatocarcinogenesis via increased cellular oxidative stress and DNA damage, as well as suppression of p53-mediated DNA damage sensing/repairing system and cell apoptosis. Targeting AR directly via either AR-small interference RNA or ASC-J9 resulted in suppression of HCC in both ex vivo cell lines and in vivo mice models.

CONCLUSIONS

Our data point to AR, but not androgens, as a potential new and better therapeutic target for the battle of HCC.

Literature-based compound profiling: application to toxicogenomics

Introduction: To reduce continuously increasing costs in drug development, adverse effects of drugs need to be detected as early as possible in the process. In recent years, compound-induced gene expression profiling methodologies have been developed to assess compound toxicity, including Gene Ontology term and pathway over-representation analyses. The objective of this study was to introduce an additional approach, in which literature information is used for compound profiling to evaluate compound toxicity and mode of toxicity. Methods: Gene annotations were built by text mining in Medline abstracts for retrieval of co-publications between genes, pathology terms, biological processes and pathways. This literature information was used to generate compound-specific keyword fingerprints, representing over-represented keywords calculated in a set of regulated genes after compound administration. To see whether keyword fingerprints can be used for assessment of compound toxicity, we analyzed microarray data sets of rat liver treated with 11 hepatotoxicants. Results: Analysis of keyword fingerprints of two genotoxic carcinogens, two nongenotoxic carcinogens, two peroxisome proliferators and two randomly generated gene sets, showed that each compound produced a specific keyword fingerprint that correlated with the experimentally observed histopathological events induced by the individual compounds. By contrast, the random sets produced a flat aspecific keyword profile, indicating that the fingerprints induced by the compounds reflect biological events rather than random noise. A more detailed analysis of the keyword profiles of diethylhexylphthalate, dimethylnitrosamine and methapyrilene (MPy) showed that the differences in the keyword fingerprints of these three compounds are based upon known distinct modes of action. Visualization of MPy-linked keywords and MPy-induced genes in a literature network enabled us to construct a mode of toxicity proposal for MPy, which is in agreement with known effects of MPy in literature. Conclusion: Compound keyword fingerprinting based on information retrieved from literature is a powerful approach for compound profiling, allowing evaluation of compound toxicity and analysis of the mode of action.

Genome-wide molecular profiles of HCV-induced dysplasia and hepatocellular carcinoma

Although HCC is the third-leading cause of cancer-related deaths worldwide, there is only an elemental understanding of its molecular pathogenesis. In western countries, HCV infection is the main etiology underlying this cancer's accelerating incidence. To characterize the molecular events of the hepatocarcinogenic process, and to identify new biomarkers for early HCC, the gene expression profiles of 75 tissue samples were analyzed representing the stepwise carcinogenic process from preneoplastic lesions (cirrhosis and dysplasia) to HCC, including 4 neoplastic stages (very early HCC to metastatic tumors) from patients with HCV infection. We identified gene signatures that accurately reflect the pathological progression of disease at each stage. Eight genes distinguish between control and cirrhosis, 24 between cirrhosis and dysplasia, 93 between dysplasia and early HCC, and 9 between early and advanced HCC. Using quantitative real-time reverse-transcription PCR, we validated several novel molecular tissue markers for early HCC diagnosis, specifically induction of abnormal spindle-like, microcephaly-associated protein, hyaluronan-mediated motility receptor, primase 1, erythropoietin, and neuregulin 1. In addition, pathway analysis revealed dysregulation of the Notch and Toll-like receptor pathways in cirrhosis, followed by deregulation of several components of the Jak/STAT pathway in early carcinogenesis, then upregulation of genes involved in DNA replication and repair and cell cycle in late cancerous stages.

CONCLUSION

These findings provide a comprehensive molecular portrait of genomic changes in progressive HCV-related HCC.

Uterine Temporal Response to Acute Exposure to 17α-Ethinyl Estradiol in the Immature Rat

The rat uterus responds to acute estrogen treatment with a series of well-characterized physiological responses; however, the gene expression changes required to elicit these responses have not been fully characterized. In order to understand early events induced by estrogen exposure in vivo, we evaluated the temporal gene expression in the uterus of the immature rat after a single dose of 17 alpha-ethinyl estradiol (EE) by microarray analysis, evaluating the expression of 15,923 genes. Immature 20-day-old rats were exposed to a single dose of EE (10 microg/kg), and the effects on uterine histology, weight, and gene expression were determined after 1, 2, 8, 24, 48, 72, and 96 h. EE induced changes in the expression of 3867 genes, at least at one time point (p < or = 0.0001), and at least 1.5-fold (up- or downregulated). Specifically, the expression of 8, 116, 3030, 2076, 381, 445, and 125 genes was modified at 1, 2, 8, 24, 48, 72, or 96 h after exposure to EE, respectively (p < or = 0.0001, t-test). At the tissue and organ level, a clear uterotrophic response was elicited by EE after only 8 h, reaching a maximum after 24 h and remaining detectable even after 96 h of exposure. The uterine phenotypic changes were induced by sequential changes in the transcriptional status of a large number of genes, in a program that involves multiple molecular pathways. Using the Gene Ontology to better understand the temporal response to estrogen exposure, we determined that the earliest changes were in the expression of genes whose products are involved in transcriptional regulation and signal transduction, followed by genes implicated in protein synthesis, energy utilization, solute transport, cell proliferation and differentiation, tissue remodeling, and immunological responses among other pathways. The compendium of genes here presented represents a comprehensive compilation of estrogen-responsive genes involved in the uterotrophic response.

Analysis of gene expression changes in relation to toxicity and tumorigenesis in the livers of Big Blue transgenic rats fed comfrey (Symphytum officinale)

Background

Comfrey is consumed by humans as a vegetable and a tea, and has been used as an herbal medicine for more than 2000 years. Comfrey, however, is hepatotoxic in livestock and humans and carcinogenic in experimental animals. Our previous study suggested that comfrey induces liver tumors by a genotoxic mechanism and that the pyrrolizidine alkaloids in the plant are responsible for mutation induction and tumor initiation in rat liver.

Results

In this study, we identified comfrey-induced gene expression profile in the livers of rats. Groups of 6 male transgenic Big Blue rats were fed a basal diet and a diet containing 8% comfrey roots, a dose that resulted in liver tumors in a previous carcinogenicity bioassay. The animals were treated for 12 weeks and sacrificed one day after the final treatment. We used a rat microarray containing 26,857 genes to perform genome-wide gene expression studies. Dietary comfrey resulted in marked changes in liver gene expression, as well as in significant decreases in the body weight and increases in liver mutant frequency. When a two-fold cutoff value and a P-value less than 0.01 were selected, 2,726 genes were identified as differentially expressed in comfrey-fed rats compared to control animals. Among these genes, there were 1,617 genes associated by Ingenuity Pathway Analysis with particular functions, and the differentially expressed genes in comfrey-fed rat livers were involved in metabolism, injury of endothelial cells, and liver injury and abnormalities, including liver fibrosis and cancer development.

Conclusion

The gene expression profile provides us a better understanding of underlying mechanisms for comfrey-induced hepatic toxicity. Integration of gene expression changes with known pathological changes can be used to formulate a mechanistic scheme for comfrey-induced liver toxicity and tumorigenesis.