Promoter hypermethylation silences cyclooxygenase-2 (Cox-2) and regulates growth of human hepatocellular carcinoma cells

Promoter methylation analysis of DKK2 may be a potential biomarker for early detection of cervical cancer

Background

Dickkopf 2 (DKK2) plays an important role in multiple cancers. Its potential value in the clinical diagnosis of cervical cancer has remained unclear.

Objectives

To investigate the expression and promoter methylation levels of DKK2 in cervical cancer and their clinicopathological associations.

Methods

We used the Gene Expression Omnibus, Oncomine, Cancer Genome Atlas, and University of ALabama at Birmingham CANcer data analysis databases, reverse transcription-PCR, and methylation-specific PCR analysis to predict and examine the expression of DKK2 mRNA and DKK2 methylation levels in cell lines and cervical cancer tissues from 79 patients with cervical cancer and 63 with cervical precancerous lesions including 25 with low-grade squamous intraepithelial lesions (LSIL) and 38 patients with high-grade squamous intraepithelial lesions (HSIL).

Results

DKK2 mRNA expression was downregulated in all cancer cell lines and cervical cancer tissues, whereas hypermethylation of DKK2 was higher in cervical cancer tissue samples. DKK2 methylation in cervical cancer was significantly higher than that in HSIL (χ2 = 8.346, P = 0.004), whereas DKK2 methylation in HSIL was significantly higher than that in normal cervical samples (χ2 = 7.934, P = 0.005) and in LSIL samples (χ2 = 4.375, P = 0.037). DKK2 silencing caused by its promoter hypermethylation was confirmed by treatment with the methyltransferase inhibitor 5-Aza-dC in cell lines. Patients with lymph node metastasis exhibited increased promoter methylation frequency (χ2 = 5.239, P = 0.022) and low DKK2 mRNA expression (χ2 = 3.958, P = 0.047) compared with patients with no lymph node metastasis. Patients with high-risk human papillomavirus infection exhibited increased promoter methylation frequency (χ2 = 6.279, P = 0.015).

Conclusions

DKK2 epigenetic changes of DKK2 may play a key role in the development of cervical cancer, suggesting that DKK2 hypermethylation could be used as a triage test for screening, early diagnosis, or risk prediction of cervical cancer.

Epigenetic regulation of the PGE2 pathway modulates macrophage phenotype in normal and pathologic wound repair

Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E2 (COX-2/PGE2) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB-mediated inflammation in diabetic wounds and show increased COX-2/PGE2 in diabetic macrophages. Further, we identify that COX-2/PGE2 production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A2/COX-2/PGE2 (cPLA2/COX-2/PGE2) pathway. We demonstrate that TGF-β-induced miRNA29b increases COX-2/PGE2 production via inhibition of DNA methyltransferase 3b-mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA2 expression and drives COX-2/PGE2. Inhibition of the COX-2/PGE2 pathway genetically (Cox2fl/fl Lyz2Cre+) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE2 pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.

The mechanistic, diagnostic and therapeutic novel nucleic acids for hepatocellular carcinoma emerging in past score years

Despite The Central Dogma states the destiny of gene as 'DNA makes RNA and RNA makes protein', the nucleic acids not only store and transmit genetic information but also, surprisingly, join in intracellular vital movement as a regulator of gene expression. Bioinformatics has contributed to knowledge for a series of emerging novel nucleic acids molecules. For typical cases, microRNA (miRNA), long noncoding RNA (lncRNA) and circular RNA (circRNA) exert crucial role in regulating vital biological processes, especially in malignant diseases. Due to extraordinarily heterogeneity among all malignancies, hepatocellular carcinoma (HCC) has emerged enormous limitation in diagnosis and therapy. Mechanistic, diagnostic and therapeutic nucleic acids for HCC emerging in past score years have been systematically reviewed. Particularly, we have organized recent advances on nucleic acids of HCC into three facets: (i) summarizing diverse nucleic acids and their modification (miRNA, lncRNA, circRNA, circulating tumor DNA and DNA methylation) acting as potential biomarkers in HCC diagnosis; (ii) concluding different patterns of three key noncoding RNAs (miRNA, lncRNA and circRNA) in gene regulation and (iii) outlining the progress of these novel nucleic acids for HCC diagnosis and therapy in clinical trials, and discuss their possibility for clinical applications. All in all, this review takes a detailed look at the advances of novel nucleic acids from potential of biomarkers and elaboration of mechanism to early clinical application in past 20 years.

Impact of DNA methyltransferase inhibitor 5-azacytidine on cardiac development of zebrafish in vivo and cardiomyocyte proliferation, apoptosis, and the homeostasis of gene expression in vitro

Cardiac development is a peculiar process involving coordinated cellular differentiation, migration, proliferation, and apoptosis. DNA methylation plays a key role in genomic stability, tissue-specific gene expression, cell proliferation, and apoptosis. Hypomethylation in the global genome has been reported in cardiovascular diseases. However, little is known about the impact and specific mechanism of global hypomethylation on cardiomyocytes. In the present study, we explored the impact of DNA methyltransferase inhibitors 5-azacytidine on cardiac development. In vivo experiment showed that hypomethylation of zebrafish embryos with 5-azacytidine exposure significantly reduced survival, induced malformations, and delayed general development process. Furthermore, zebrafish embryos injected with 5-azacytidine developed pericardial edema, ventricular volume reduction, looping deformity, and reduction in heart rate and ventricular shortening fraction. Cardiomyocytes treated with 5-azacytidine in vitro decreased proliferation and induced apoptosis in a concentration-dependent manner. Furthermore, 5-azacytidine treatment in cardiomyocytes resulted in 20 downregulated genes expression and two upregulated genes expression in 45 candidate genes, which indicated that DNA methylation functions as a bidirectional modulator in regulating gene expression. In conclusion, these results show the regulative effects of the epigenetic modifier 5-azacytidine in cardiac development of zebrafish embryos in vivo and cardiomyocyte proliferation and apoptosis and the homeostasis of gene expression in vitro, which offer a novel understanding of aberrant DNA methylation in the etiology of cardiovascular disease.

Epigenetic regulation of COX‑2 expression by DNA hypomethylation via NF‑κB activation in ketamine‑induced ulcerative cystitis

The present study investigated the methylation of CpG sites in the cyclooxygenase (COX)-2 promoter via nuclear factor (NF)-κB transcriptional regulation and elucidated its effect on the COX-2 transcriptional expression in a ketamine-induced ulcerative cystitis (KIC) animal model. The results of the present study revealed that ketamine treatment induced NF-κB p65 translocation to nuclei and activated COX-2 expression and prostaglandin (PGE)2 production in bladder tissue, whereas COX-2 inhibitor suppressed the inflammatory effect. Moreover, DNA hypomethylation of the COX-2 promoter region located from -1,522 to -829 bp might contribute to transcriptional regulation of COX-2 expression and induce a pro-inflammatory response in KIC. Ketamine treatment increased the binding of NF-κB and permissive histone H3 lysine-4 (H3K4)m3, but caused a decrease in the repressive histone H3K27m3 and H3K36m3 on the COX-2 promoter ranging from -1,522 to -1,331 bp as determined by a chromatin immunoprecipitation assay. Moreover, in the ketamine group, the level of Ten-Eleven-Translocation methylcytosine dioxygenase for demethylation as determined by reverse transcription-quantitative PCR assay was increased in comparison with the control group, but that was not the case for the level of DNA methyltransferases for methylation. The present findings revealed that there was a hypomethylation pattern of the COX-2 promoter in association with the level of COX-2 transcription in KIC.

Transcriptome analysis identifies metallothionein as biomarkers to predict recurrence in hepatocellular cacinoma

BACKGROUND

Liver cancer is the fifth most common cancer, and hepatocellular carcinoma (HCC) is the major liver tumor type seen in adults. HCC is usually caused by chronic liver disease such as hepatitis B virus or hepatitis C virus infection. One of the promising treatments for HCC is liver transplantation, in which a diseased liver is replaced with a healthy liver from another person. However, recurrence of HCC after surgery is a significant problem. Therefore, it is important to discover reliable cellular biomarkers that can predict recurrence in HCC.

METHODS

We analyzed previously published HCC RNA-Seq data that includes 21 paired tumor and normal samples, in which nine tumors were recurrent after orthotopic liver transplantation and 12 were nonrecurrent tumors with their paired normal samples. We used both the reference genome and de novo transcriptome assembly based analyses to identify differentially expressed genes (DEG) and used RandomForest to discover biomarkers.

RESULTS

We obtained 398 DEG using the Reference approach and 412 DEG using de novo assembly approach. Among these DEG, 258 genes were identified by both approaches. We further identified 30 biomarkers that could predict the recurrence. We used another independent HCC study that includes 50 patients normal and tumor samples. By using these 30 biomarkers, the prediction accuracy was 100% for normal condition and 98% for tumor condition. A group of Metallothionein was specifically discovered as biomarkers in both reference and de novo assembly approaches.

CONCLUSION

We identified a group of Metallothionein genes as biomarkers to predict recurrence. The metallothionein genes were all down-regulated in tumor samples, suggesting that low metallothionein expression may be a promoter of tumor growth. In addition, using de novo assembly identified some unique biomarkers, further confirmed the necessity of conducting a de novo assembly in human cancer study.

Mechanistic Effects of Calcitriol in Cancer Biology

Besides its classical biological effects on calcium and phosphorus homeostasis, calcitriol, the active vitamin D metabolite, has a broad variety of actions including anticancer effects that are mediated either transcriptionally and/or via non-genomic pathways. In the context of cancer, calcitriol regulates the cell cycle, induces apoptosis, promotes cell differentiation and acts as anti-inflammatory factor within the tumor microenvironment. In this review, we address the different mechanisms of action involved in the antineoplastic effects of calcitriol.

Epigenetic regulations of inflammatory cyclooxygenase-derived prostanoids: molecular basis and pathophysiological consequences

The potential relevance of prostanoid signaling in immunity and immunological disorders, or disease susceptibility and individual variations in drug responses, is an important area for investigation. The deregulation of Cyclooxygenase- (COX-) derived prostanoids has been reported in several immunoinflammatory disorders such as asthma, rheumatoid arthritis, cancer, and autoimmune diseases. In addition to the environmental factors and the genetic background to diseases, epigenetic mechanisms involved in the fine regulation of prostanoid biosynthesis and/or receptor signaling appeared to be an additional level of complexity in the understanding of prostanoid biology and crucial in controlling the different components of the COX pathways. Epigenetic alterations targeting inflammatory components of prostanoid biosynthesis and signaling pathways may be important in the process of neoplasia, depending on the tissue microenvironment and target genes. Here, we focused on the epigenetic modifications of inflammatory prostanoids in physiological immune response and immunological disorders. We described how major prostanoids and their receptors can be functionally regulated epigenetically and consequently the impact of these processes in the pathogenesis inflammatory diseases and the development of therapeutic approaches that may have important clinical applications.

Transforming growth factor-β induces microRNA-29b to promote murine alveolar macrophage dysfunction after bone marrow transplantation

Hematopoietic stem cell transplantation (HSCT) is complicated by pulmonary infections that manifest posttransplantation. Despite engraftment, susceptibility to infections persists long after reconstitution. Previous work using a murine bone marrow transplant (BMT) model implicated increased cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) in promoting impaired alveolar macrophage (AM) responses. However, mechanisms driving COX-2 overexpression remained elusive. Previously, transforming growth factor-β (TGF-β) signaling after BMT was shown to promote hypomethylation of the COX-2 gene. Here, we provide mechanistic insight into how this occurs and show that TGF-β induces microRNA (miR)-29b while decreasing DNA methyltransferases (DNMT)1, DNMT3a, and DNMT3b in AMs after BMT. De novo DNMT3a and DNMT3b were decreased upon transient transfection of miR-29b, resulting in decreased methylation of the COX-2 promoter and induction of COX-2. As a consequence, miR-29b-driven upregulation of COX-2 promoted AM dysfunction, and transfection of BMT AMs with a miR-29b inhibitor rescued the bacterial-killing defect. MiR-29b-mediated defects in BMT AMs were dependent on increased levels of PGE2, as miR-29b-transfected AMs treated with a novel E prostanoid receptor 2 antagonist abrogated the impaired bacterial killing. We also demonstrate that patients that have undergone HSCT exhibit increased miR-29b; thus these studies highlight miR-29b in driving defective AM responses and identify this miRNA as a potential therapeutic target.

p50-associated COX-2 extragenic RNA (PACER) activates COX-2 gene expression by occluding repressive NF-κB complexes

Deregulated expression of COX-2 has been causally linked to development, progression, and outcome of several types of human cancer. We describe a novel fundamental level of transcriptional control of COX-2 expression. Using primary human mammary epithelial cells and monocyte/macrophage cell lines, we show that the chromatin boundary/insulator factor CTCF establishes an open chromatin domain and induces expression of a long non-coding RNA within the upstream promoter region of COX-2. Upon induction of COX-2 expression, the lncRNA associates with p50, a repressive subunit of NF-κB, and occludes it from the COX-2 promoter, potentially facilitating interaction with activation-competent NF-κB p65/p50 dimers. This enables recruitment of the p300 histone acetyltransferase, a domain-wide increase in histone acetylation and assembly of RNA Polymerase II initiation complexes. Our findings reveal an unexpected mechanism of gene control by lncRNA-mediated repressor occlusion and identify the COX-2-lncRNA, PACER, as a new potential target for COX-2-modulation in inflammation and cancer.

DOI:http://dx.doi.org/10.7554/eLife.01776.001

To produce a protein a cell must first transcribe the DNA in a gene to make a messenger RNA molecule, which is then translated to make the protein. However, cells also produce other types of RNA molecules which do not become proteins. MicroRNAs, for example, regulate the expression of genes as proteins, while the role of other RNA molecules called long non-coding RNAs (lncRNAs) is not well understood.

Now Krawczyk and Emerson have found an lncRNA that controls a gene called COX-2 that is often implicated in breast, colon, prostate, and lung cancer. This RNA molecule, which is called PACER, originates near the start of the COX-2 gene, but it cannot be messenger RNA because it does not contain the instructions to make the COX-2 protein, and it is too long to be a microRNA. Further experiments showed that the newly discovered lncRNA activates the expression of the COX-2 gene.

Krawczyk and Emerson found that PACER attracts enzymes that spotlight genes that need to be activated, thus increasing the transcription of these genes to make messenger RNA. Genes can also be switched on and off by various molecules binding to nearby DNA, and PACER encourages the activation of COX-2 by keeping away the molecules that might switch it off.

In addition to shedding new light on the role of lncRNAs, these results suggest that PACER could be a suitable therapeutic target in cancers that involve the COX-2 gene.

DOI:http://dx.doi.org/10.7554/eLife.01776.002

Aberrant promoter methylation and silencing of RASSF2A gene in cervical cancer

AIM

Ras association domain family (RASSF)2A as a negative effector of Ras protein is inactivated by promoter hypermethylation in many cancers. This study evaluated the methylation status of RASSF2A in cervical cancer (CC) and its correlation with clinicopathological characteristics.

METHODS

Methylation-specific polymerase chain reaction and reverse transcriptase polymerase chain reaction were utilized to analyze the methylation status and RASSF2A mRNA expression in four CC cell lines and tissue samples from 25 normal controls and 46 CC patients. The CC cell lines also were treated with the methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC).

RESULTS

Expression of RASSF2A was downregulated in all cell lines and CC tissue samples. Hypermethylation of RASSF2A was detected in all cell lines and 26 of 46 (56.5%) CC samples. No methylation of RASSF2A was found in the normal cervical tissues. A decreased level (P < 0.05) of RASSF2A expression was observed among RASSF2A-methylated CC cases (0.1002 ± 0.0377, mean ± standard deviation) compared to unmethylated cases (0.2882 ± 0.0642, mean ± standard deviation). After treatment with 5-aza-dC, loss of RASSF2A expression was restored in four CC cell lines. RASSF2A methylation was significantly different in patients with or without lymph node metastasis (90% vs 47.2%, respectively; P < 0.05).

CONCLUSION

Promoter hypermethylation of RASSF2A is observed in CC, while not in normal cervical tissues. RASSF2A is inactivated in CC by promoter hypermethylation and may play a role in cervical carcinogenesis.

Target genes discovery through copy number alteration analysis in human hepatocellular carcinoma

High-throughput short-read sequencing of exomes and whole cancer genomes in multiple human hepatocellular carcinoma (HCC) cohorts confirmed previously identified frequently mutated somatic genes, such as TP53, CTNNB1 and AXIN1, and identified several novel genes with moderate mutation frequencies, including ARID1A, ARID2, MLL, MLL2, MLL3, MLL4, IRF2, ATM, CDKN2A, FGF19, PIK3CA, RPS6KA3, JAK1, KEAP1, NFE2L2, C16orf62, LEPR, RAC2, and IL6ST. Functional classification of these mutated genes suggested that alterations in pathways participating in chromatin remodeling, Wnt/β-catenin signaling, JAK/STAT signaling, and oxidative stress play critical roles in HCC tumorigenesis. Nevertheless, because there are few druggable genes used in HCC therapy, the identification of new therapeutic targets through integrated genomic approaches remains an important task. Because a large amount of HCC genomic data genotyped by high density single nucleotide polymorphism arrays is deposited in the public domain, copy number alteration (CNA) analyses of these arrays is a cost-effective way to reveal target genes through profiling of recurrent and overlapping amplicons, homozygous deletions and potentially unbalanced chromosomal translocations accumulated during HCC progression. Moreover, integration of CNAs with other high-throughput genomic data, such as aberrantly coding transcriptomes and non-coding gene expression in human HCC tissues and rodent HCC models, provides lines of evidence that can be used to facilitate the identification of novel HCC target genes with the potential of improving the survival of HCC patients.

Enhanced 5-fluorouracil cytotoxicity in high COX-2 expressing hepatocellular carcinoma cells by wogonin via the PI3K/Akt pathway

Combination therapies may increase the antitumor effects and reduce the adverse effects for the treatment of hepatocellular carcinoma. In this study, we determined the effects of 5-fluorouracil alone or in combination with wogonin in vitro and in vivo, and we investigated the possible mechanisms. The combination of these 2 drugs led to a decrease in survival and a significant synergistic inhibitory effect on high COX-2 expression in SMMC-7721 hepatocellular carcinoma (HCC) cells. Furthermore, the results show that this combination inhibits COX-2 expression and increases sensitivity to chemotherapeutic agents partly through regulating the PI3K/Akt signaling pathway. Moreover, the combination treatment caused a significant growth inhibition of human tumor xenografts in vivo. In conclusion, wogonin may increase the cytotoxicity of some antineoplastic agents and it can be used in combination with these agents as a novel therapeutic regimen for HCC treatment.

5-Aza-2'-deoxycytidine enhances maspin expression and inhibits proliferation, migration, and invasion of the bladder cancer T24 cell line

BACKGROUND

Downregulation of maspin expression has been linked to bladder cancer development, and that DNA methylation may be important for regulating maspin gene activation in bladder cancer cells. Thus, we attempted to explore the effects of the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-Aza-CdR), on the maspin expression and the biological behaviors in bladder cancer T24 cells.

METHOD

The methylation status of maspin in T24 cells was investigated by methylation-specific polymerase chain reaction (PCR). After treated with different concentrations of 5-Aza-CdR (0, 0.25, 0.5, 1, and 2 μM), the maspin gene mRNA expression and protein expression were examined by real-time PCR and western blotting analysis. Cell proliferations were evaluated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Flow cytometry was used to identify the apoptosis rates. Migration and invasive ability were determined by the transwell assay. Using the western blotting analysis, the changes of Cyclin D1, VEGF-C, VEGFR-3, MMP-2, MMP-9, caspase-3 p17, Bax, and Bcl-2 expression were measured.

RESULTS

Promoter DNA methylation of maspin was observed in T24 cells. The expression levels of maspin mRNA and protein in T24 cells were increased in a dose manner after treatment with increasing 5-Aza-CdR (p<0.05). The proliferation, migration, and invasion of cells were significantly inhibited with increasing 5-Aza-CdR, whereas the apoptosis was greatly increased (p<0.05). These were associated with the decreased ratio of Bcl-2/Bax, activation of caspase-3, and decreased expression of Cyclin D1, VEGF-C, VEGFR-3, MMP-2 and MMP-9.

CONCLUSIONS

The present study demonstrates that maspin is silenced by DNA methylation in bladder T24 cells, and its expression can be reactivated by treatment with 5-Aza-CdR. 5-Aza-CdR could result in obvious inhibitions of the proliferation, migration, and invasion of T24 cells, which may serve as a potential strategy for the treatment of bladder cancer.

Combination of celecoxib and doxorubicin increases growth inhibition and apoptosis in acute myeloid leukemia cells

Cyclooxygenase-2 (COX-2) inhibitors have been shown to enhance antitumor activity of therapeutic agents in a variety of solid tumor cells. However, this has not been well established in hematopoietic tumors, especially in acute myeloid leukemia (AML). This study was designed to investigate the effects of the combination of celecoxib, a specific COX-2 inhibitor, and doxorubicin on cell growth and apoptosis in human leukemia cells. Co-treatment with celecoxib and doxorubicin significantly inhibited cell growth and induced cell apoptosis in the acute leukemia cell line HL60 and primary AML cells. The growth inhibition effect was accompanied by down-regulation of the expression of cyclin E and cyclin-dependent kinase 2 (CDK2), the key regulators of cell cycle progression, which was associated with arrest of cells at G0/G1 phase. The pro-apoptotic effect was accompanied by down-regulation of the expression of survivin, an inhibitor of apoptosis protein, which mediated anti-apoptosis in AML cells. These results provide the first evidence that the growth inhibitory and pro-apoptotic effects of celecoxib and doxorubicin on AML cells are synergistic.

Correlation of epigenetic change and identification of risk factors for oral submucous fibrosis

BACKGROUND

DNA methylation of certain genes is an epigenetic change that is essential for tumorigenesis. Oral submucous fibrosis (OSF) is a precancerous condition of oral mucosa with inflammation and progressive fibrosis of the lamina propria and deeper connective tissue. The hypermethylation of E-cadherin and cyclooxygenase 2 (COX-2) in chronic inflammation may demonstrate a mild lesion/mutation at epigenetic levels. This study compares the hypermethylation status of E-cadherin and COX-2 genes in patients with oral cancer and patients with OSF and also aims to identify risk factors for the development of OSF.

METHODS

DNA was extracted from blood samples of 50 healthy subjects, 50 patients with OSF and 60 patients with oral cancer. Methylation-specific polymerase chain reaction for E-cadherin and COX-2 was performed on these samples and the products were analyzed on 2% agarose gel. Surveys about oral health habits and clinical periodontal examinations in patients with OSF and healthy subjects were also conducted by well-trained dentists, and logistic regression was performed to identify risk factors for OSF.

RESULTS

Hypermethylation of E-cadherin and COX-2 was observed in 36% and 22% of oral cancer samples, respectively. In patients with OSF, the rates were 52% and 30%, and in healthy controls the rates were 4% and 6%. Hypermethylation was shown to be correlated between the 3 groups with statistical significance (p<0.01). Methylation of CpG islands in E-cadherin and COX-2 occurred more frequently in patients with OSF than in the control group, but less frequently than in patients with oral cancer. In the logistic regression analysis, smoking, brushing more than twice daily, periodontal probing depth and plaque index were identified as 4 major risk factors for OSF.

CONCLUSIONS

These data confirm that E-cadherin and COX-2 expressions are related to OSF. The epigenetic changes presented in patients with chronic inflammation might demonstrate an irreversible destruction in the tissues or organs similar to the effects of cancer. Chronic OSF was significantly associated with hypermethylation, a cancer risk factor.

Evaluation of epigenetic modulation of cyclooxygenase-2 as a prognostic marker for hepatocellular carcinoma

Cyclooxygenases (COX-1 and 2) catalyze the first step in prostanoid biosynthesis. They are implicated in homeostatic processes with an important role in inflammation and carcinogenesis. In the liver, COX-2 expression is restricted to proliferation or dedifferentiation situations. The COX-2 promoter contains numerous CpG islands that, when hypermethylated, result in transcriptionally silencing thus regulating the growth of carcinoma cells. In this work, we investigated whether a correlation exists between COX-2 expression and methylation signatures at the 5'region of the gene in hepatoma cell lines and human hepatocellular carcinoma (HCC). We also examined the acetylation status of the COX-2 promoter and the effects of histone deacetylase (HDAC) inhibitors on COX-2 expression. Our results suggest a significant association between reduced COX-2 expression and promoter hypermethylation of COX-2 and histone deacetylation in some hepatoma cell lines and in HCC. Treatment with demethylating agents or HDAC inhibitors restored the expression of COX-2. Moreover, in an HCC cohort, a statistically significant inverse association was observed between COX-2 mRNA levels and promoter methylation. In agreement with these data, a reduction of overall survival of the patients was observed after decreased COX-2 expression by promoter hypermethylation and histone H3 hypoacetylation.

Integrative array-based approach identifies MZB1 as a frequently methylated putative tumor suppressor in hepatocellular carcinoma

PURPOSE

The aim of this study was the identification of novel tumor suppressor genes (TSG) silenced by DNA hypermethylation in hepatocellular carcinoma (HCC).

EXPERIMENTAL DESIGN

We conducted integrative array-based approach for genome-wide screening of methylation targets using a methylated DNA immunoprecipitation-CpG island microarray and expression array in three universal hepatoma cell lines and normal liver tissue. Through detailed expression and functional analyses using hepatoma cell lines and primary HCC samples, we isolated novel TSGs for HCC.

RESULTS

A total of 642 genes were identified as methylated in three hepatoma cell lines but unmethylated in normal liver tissue, whereas 204 genes on autosomes were identified as genes unexpressed but restored after treatment with 5-aza-2'-deoxycytidine in these cell lines and expressed in normal tissue. Through the integration of results of the two-array analyses and further validation analyses of expression and methylation status in 17 cell lines and 30 primary tumors of hepatoma, we identified MZB1, marginal zone B and B1 cell-specific protein, encoding an endoplasmic reticulum protein, as a putative TSG frequently methylated within its CpG island in hepatoma. Among 162 patients with primary HCC, silencing of MZB1 protein was significantly and independently associated with a worse outcome. Restoration of MZB1 expression in hepatoma cells reduced cell proliferation in vitro and in vivo through G(1)-arrest.

CONCLUSIONS

These results suggest that methylation-mediated silencing of MZB1 expression leads to loss of its tumor-suppressive activity, which may be a factor in the hepatocarcinogenesis, and is a useful prognosticator in HCC.

Epigenetic deregulation of the COX pathway in cancer

Inflammation is a major cause of cancer and may condition its progression. The deregulation of the cyclooxygenase (COX) pathway is implicated in several pathophysiological processes, including inflammation and cancer. Although, its targeting with nonsteroidal antiinflammatory drugs (NSAIDs) and COX-2 selective inhibitors has been investigated for years with promising results at both preventive and therapeutic levels, undesirable side effects and the limited understanding of the regulation and functionalities of the COX pathway compromise a more extensive application of these drugs. Epigenetics is bringing additional levels of complexity to the understanding of basic biological and pathological processes. The deregulation of signaling and biosynthetic pathways by epigenetic mechanisms may account for new molecular targets in cancer therapeutics. Genes of the COX pathway are seldom mutated in neoplastic cells, but a large proportion of them show aberrant expression in different types of cancer. A growing body of evidence indicates that epigenetic alterations play a critical role in the deregulation of the genes of the COX pathway. This review summarizes the current knowledge on the contribution of epigenetic processes to the deregulation of the COX pathway in cancer, getting insights into how these alterations may be relevant for the clinical management of patients.

Promoter methylation regulates cigarette smoke-stimulated cyclooxygenase-2 expression in esophageal squamous cell carcinoma

OBJECTIVE

Cigarette smoke extracts (CSE) could promote esophageal squamous cell carcinoma (ESCC) through upregulation of cyclooxygenase-2 (COX-2) expression. Promoter methylation mediates the transcriptional modulation of the COX-2 gene. The aim of the study was to explore whether COX-2 promoter methylation regulated COX-2 expression and functional activity in ESCC exposed to CSE.

METHODS

The methylation status of COX-2 promoter in two human ESCC cell lines, EC109 and TE-1, was examined using bisulfite sequencing analysis. COX-2 mRNA and protein expression were detected by reverse-transcription polymerase chain reaction and Western blot. Prostaglandin E₂ (PGE₂) was examined by enzyme linked immunosorbent assay (ELISA).

RESULTS

The promoter was hypermethylated in TE-1 which had a low level of COX-2 expression and was hypomethylated in EC109 with a relatively high level of COX-2 expression. Stimulation by cigarette smoke ethanol extract (EE) resulted in increased COX-2 expression in EC109, but not in TE-1. Treatment with 5-aza-2'-deoxycytidine (5-aza-DC) demethylated the promoter and upregulated COX-2 expression as well as PGE(2) production in TE-1, especially followed by EE stimulation. No significant effect was observed in EC109.

CONCLUSION

These findings suggest that promoter methylation may be one of the mechanisms regulating COX-2 expression in ESCC in response to stimulation of CSE.

Promoter hypermethylation of cyclooxygenase-2 gene in esophageal squamous cell carcinoma

Cyclooxygenase-2 (COX-2) is overexpressed in various types of human malignancies including esophageal squamous cell carcinoma (ESCC). However, a subset of ESCC either do not express COX-2 or show low level of expression. It is well established that promoter methylation is a major mechanism that mediates transcriptional silencing of COX-2 in gastric and colorectal cancer, but the data on ESCC are very limited. In this study, we attempted to determine whether COX-2 expression was also regulated by promoter methylation in human ESCC cell lines. We examined the methylation status of the COX-2 promoter in five human ESCC cell lines (EC109, EC9706, KYSE 410, KYSE 150, TE-1) using bisulfite sequencing analysis. Western blot analysis was used to determine COX-2 expression. Quantitative real-time polymerase chain reaction was used to determine COX-2 mRNA level. Prostaglandin (PG) E(2) was detected by ELISA. The promoter was densely methylated in TE-1 and KYSE 150, which had a low level of COX-2 expression and less methylated in other three cell lines (EC109, EC9706, KYSE 410), with high level of COX-2 expression. Treatment with 5-aza-deoxycytidine (5-aza-DC), a DNA methyltransferase inhibitor, demethylated the promoter and upregulated COX-2 expression, as well as PGE(2) production in TE-1 and KYSE 150. However, no such effects were observed in EC109. COX-2 protein was negative, but mRNA was positive in TE-1. After treatment with 5-aza-DC, both COX-2 mRNA and protein level had increased. These findings suggest that the promoter methylation may be one of the mechanisms that regulate COX-2 expression in ESCC.

Methylation status and overexpression of COX-2 in Tunisian patients with ductal invasive breast carcinoma

Inflammation and hormonal signalling induce the cyclooxygenase-2 (COX-2) expression in solid tumours including breast cancer, which in turn affects cell proliferation, apoptosis and metastasis. The aim of this study was to investigate the expression of COX-2 and its association with clinical parameters, patient's survival, hormones receptors (oestrogen, progesterone), ERBB2 and TP53 expression in 83 cases of infiltrating ductal breast carcinomas. Moreover, the methylation status at the CpG islands of the COX-2 gene promoter was also explored in 70 specimens. We showed that tumours exhibiting moderate to intense COX-2 immunostaining were significantly more frequent in patients over 45 years old (p = 0.027). Moreover, a high level of COX-2 expression correlated with a shorter survival time (p log-rank = 0.04) and was an independent prognostic factor (p = 0.022; HR 6.4; 95% CI = 1.3-31.4). On the other hand, hypermethylation of the COX-2 gene promoter was observed in 27% of cases and strongly associated with smaller tumours (<5 cm, p = 0.011). Furthermore, patients with methylated COX-2 pattern have a better 4-year disease-free survival (p = 0.022) as well as a prolonged overall survival (p log-rank test = 0.034). In conclusion, we showed that high COX-2 expression was associated with reduced survival and was an independent prognostic factor. However, hypermethylation of the COX-2 promoter correlated with a better overall survival in Tunisian patients with breast carcinoma.

Preventing chemoresistance of human breast cancer cell line, MCF-7 with celecoxib

PURPOSE

To investigate the preventive effect of celecoxib, a specific cyclooxygenase-2 (Cox-2) inhibitor, on the development of chemoresistance in breast cancer cell line, MCF-7, and explore the mechanism of the action.

METHODS

Chemoresistance phenotype was established by treating MCF-7 cells with 0.05 μg/ml doxorubicin for 7 days, and then the effect of preventive chemoresistance was investigated by the combination of same dose of doxorubicin with 10 μM celecoxib. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay was used to assess cytostatic efficacy of doxorubicin and 50% inhibiting concentration (IC(50)) of MCF-7 cells. RT-PCR was performed to examine mRNA expression of multidrug resistance gene 1 (MDR1) and its transcription factors c-Jun and NF-κB. Western blotting analysis was performed to detect the expression of protein. Flow cytometry (FCM) was applied to analyze the expression and function of P-glycoprotein (P-gp). Electrophoretic gel mobility shift assay (EMSA) was performed to determine the DNA-binding activity of nuclear transcription factors AP-1 and NF-κB.

RESULTS

Compared with sensitive MCF-7 cells, MDR1 and its transcription factors c-Jun and NF-κB were up-regulated at both mRNA level (P < 0.01) and protein level (P < 0.01) by treatment with 0.05 μg/ml doxorubicin for 7 days. After co-incubation with both the same dose of doxorubicin and 10 μM celecoxib for 7 days, both mRNA level and protein level of MDR1, c-Jun and NF-κB up-regulated by doxorubicin were partly reversed (P < 0.01); DNA-binding activity of nuclear transcription factors AP-1 and NF-κB were inhibited; and the function of P-gp was decreased (P < 0.01). When MCF-7 cells were treated with increasing doses of doxorubicin in the presence of 10 μM celecoxib, IC50 value of doxorubicin and doxorubicin plus 10 μM celecoxib was 0.67 ± 0.03 and 0.38 ± 0.04 μg/ml, respectively (P < 0.01).

CONCLUSION

Celecoxib effectively prevents the development of chemoresistance in breast cancer cell line MCF-7 induced by doxorubicin, which was partly involved in inhibiting the expression and DNA-binding activity of nuclear transcription factors AP-1 and NF-κB and downstream expression and function of P-gp. Furthermore, cytostatic efficacy of celecoxib and doxorubicin on MCF-7 cell was synergistic.

Sustained JNK1 activation is associated with altered histone H3 methylations in human liver cancer

BACKGROUND/AIMS

Aberrant c-Jun N-terminal kinase (JNK) activation has been linked to hepatocellular carcinoma (HCC) in mouse models. It remains unclear whether JNK activation plays an important role in human HCC and, if so, how JNK signaling contributes to the initiation or progression of HCC.

METHODS

The JNK activation, global gene expression, and the status of histone H3 methylations were measured in 31 primary human hepatocellular carcinoma (HCC) samples paired with the adjacent non-cancerous (ANC) tissues.

RESULTS

Enhanced JNK1 activation was noted in 17 out of 31 HCC samples (55%) relative to the corresponding ANC tissues, whereas JNK2 activation was roughly equal between HCC and ANC tissues. This enhancement in JNK1 activation is associated with an increased tumor size and a lack of encapsulation of the tumors. In addition, an association of JNK1 activation with the histone H3 lysines 4 and 9 tri-methylation was observed in the HCC tissues, which leads to an elevated expression of genes regulating cell growth and a decreased expression of the genes for cell differentiation and the p450 family members in HCC.

CONCLUSIONS

These results, thus, suggest that JNK1 plays important roles in the development of human HCC partially through the epigenetic mechanisms.

The COX-2/PGE2 pathway: key roles in the hallmarks of cancer and adaptation to the tumour microenvironment

It is widely accepted that alterations to cyclooxygenase-2 (COX-2) expression and the abundance of its enzymatic product prostaglandin E(2) (PGE(2)) have key roles in influencing the development of colorectal cancer. Deregulation of the COX-2/PGE(2) pathway appears to affect colorectal tumorigenesis via a number of distinct mechanisms: promoting tumour maintenance and progression, encouraging metastatic spread, and perhaps even participating in tumour initiation. Here, we review the role of COX-2/PGE(2) signalling in colorectal tumorigenesis and highlight its ability to influence the hallmarks of cancer--attributes defined by Hanahan and Weinberg as being requisite for tumorigenesis. In addition, we consider components of the COX-prostaglandin pathway emerging as important regulators of tumorigenesis; namely, the prostanoid (EP) receptors, 15-hydroxyprostaglandin dehydrogenase and the prostaglandin transporter. Finally, based on recent findings, we propose a model for the cellular adaptation to the hypoxic tumour microenvironment that encompasses the interplay between COX-2, hypoxia-inducible factor 1 and dynamic switches in beta-catenin function that fine-tune signalling networks to meet the ever-changing demands of a tumour.

Silencing of Hint1, a novel tumor suppressor gene, by promoter hypermethylation in hepatocellular carcinoma

The Hint1 protein, a member of the histidine triad (HIT) family, is highly conserved in diverse species and ubiquitously expressed in mammalian tissues. Previous studies in mice provided evidence that Hint1 may be haploinsufficient with respect to its function as a tumor suppressor. In the present study, we investigated the aberrant methylation of Hint1 and explored possible relationships between aberrant methylation and clinicopathological features in hepatocellular carcinoma (HCC). Hypermethylation of Hint1 was evaluated by the methylation specific PCR (MSP) method in 40 patients with HCC (tumor and paired adjacent non-tumor tissues) from Taiwan, 22 cases of normal liver tissue (14 from Taiwan and 8 from the US). HINT1 expression in tissues was detected by immunohistochemistry. The frequencies of hypermethylation of Hint1 in tumor, paired adjacent non-tumor and normal liver tissue were 55.0%, 37.5% and 9.1%, respectively. A statistically significant inverse association was found between Hint1 methylation status and expression of the HINT1 protein in tumor tissues (p=0.003). The relationship between Hint1 methylation status and clinical features and other, previously measured biomarkers was also analyzed. p16 hypermethylation was statistically significantly associated with Hint1 methylation status (p=0.035). There were no correlations between Hint1 methylation and hepatitis B (HBV) or hepatitis C (HCV) infection status or aflatoxin B(1) (AFB(1)-) and polycyclic aromatic hydrocarbons (PAHs)-DNA adduct levels. These results suggest that promoter hypermethylation of Hint1 may play a role in hepatocarcinogenesis.

Promoter methylation of SFRPs gene family in cervical cancer

OBJECTIVES

Oncogenic activation of the Wnt/beta-catenin signaling pathway is common in human cancers, including cervical cancer. The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and play an important role in carcinogenesis. Frequent promoter hypermethylation of SFRPs has been identified in human cancers; however, the precise role of SFRPs in cervical cancer is not clear.

METHODS

The methylation status of SFRPs gene family was analyzed in two cervical cancer cell lines and a full spectrum of cervical neoplasia, including 45 low-grade squamous intraepithelial lesions (LSIL), 49 high-grade squamous intraepithelial lesions (HSIL), 109 squamous cell carcinomas (SCC), and 45 normal controls.

RESULTS

The SFRP1 promoter was hypermethylated in 33.9% of SCC, 8.2% of HSIL, 2.2% of LSIL, but not in normal tissues. The SFRP2 promoter was hypermethylated in 80.7% of SCC, 16.3% of HSIL, 15.6% LSIL and 4.4% normal tissues. The SFRP4 promoter was hypermethylated in 67.9% of SCC, 36.7% of HSIL, 4.4% of LSIL, but not in normal tissues. The SFRP5 promoter was hypermethylated in 10.1% of SCC, 4.1% of HSIL, 13.3% of LSIL and 4.4% normal tissues. The frequency of SFRP1, SFRP2 and SFRP4 promoter methylation in tumors was significantly higher than in normal, LSIL, and HSIL samples (P<0.0001). SFRP5 methylation was significantly different in patients with or without lymph-node metastases (0% vs 15.2%, respectively, P<0.05).

CONCLUSIONS

Our data suggest that promoter hypermethylation of SFRP1, SFRP2 and SFRP4 is associated with cervical carcinogenesis, which could be used for molecular screening of cervical neoplasias in future.

Synergistic interaction between excess hepatic iron and alcohol ingestion in hepatic mutagenesis

BACKGROUND/AIM

Hereditary hemochromatosis (HH) and dietary iron overload are the main iron-loading diseases. Fibrosis, cirrhosis and hepatocellular carcinoma (HCC) are complications to HH and dietary iron overload possibly influenced by co-factors. Alcohol may be one such factor. The aim therefore was to determine the extent of synergistic interaction between free hepatic iron and alcohol, complicating dietary iron overload in HCC pathogenesis.

METHODS

Four groups of 20 Wistar albino rats were used: group 1 (C) was fed the chow diet; group 2 (Fe) was supplemented with 0.75% ferrocene iron; group 3 (Fe+Al), 0.75% iron and 7% ethanol; and group 4, 7% ethanol (Al) for 12 months. Iron profile, superoxide/nitrite free radicals, lipid peroxidation (LPO)/8-isoprostane (8-IP), 8-hydroxydeoxyguanosine (8-OHdG), oxidative lipid/DNA damage immunohistochemistry, transaminases (AST/ALT) and Ames mutagenesis tests were performed.

RESULTS

Significant differences were observed in the Fe+Al group for LPO, 8-IP, AST and ALT (p<0.001, 0.001, 0.001 and 0.001, respectively) compared to other groups. A three-fold synergistic interaction was observed for the same parameters. Furthermore, significant differences of p<0.05 and 0.001 were observed for 8-OHdG and mutagenesis, respectively, with an additive synergy in the Fe+Al group. ALT/8-OHdG and ALT/mutagenesis correlated positively (p<0.04 and 0.008, respectively). The immunohistochemistry revealed iron/alcohol multiplicative synergism with hydroxyl radical involvement.

CONCLUSION

Mutagenic effects of iron and alcohol are synergistically multiplicative implicating hydroxyl free radicals in hepatocarcingenesis.

SFRP1 suppressed hepatoma cells growth through Wnt canonical signaling pathway

Oncogenic activation of the Wnt/beta-catenin signaling pathway is common in hepatocellular carcinoma (HCC). The secreted frizzled-related proteins (SFRPs) function as negative regulators of Wnt signaling and have important implications for carcinogenesis. Promoter hypermethylation of SFRP genes is common in human cancers. However, the role of SFRPs in HCC is not clear. Recently, we have shown that SFRP1 is frequently downregulated through promoter hypermethylation. To confirm and extend these findings, the methylation status of the other SFRP members, including SFRP2, SFRP4 and SFRP5, was examined by methylation-specific polymerase chain reaction (MS-PCR). Hypermethylation of SFRP genes, except for SFRP4, is frequent in HCCs and the levels found here were significantly higher than those seen in cirrhotic livers, chronic hepatitis livers and normal controls (p < 0.0001 for SFRP1 and SFRP2, p < 0.05 for SFRP5). To investigate the role of SFRP1 in HCCs, we used re-expression of SFRP1 in beta-catenin-dependent HCC cell lines: Huh6 and HepG2. Restoration of SFRP1 attenuated Wnt signaling in those Huh6 hepatoma cells with a beta-catenin gene point mutation, decreased abnormal accumulation of beta-catenin in the nucleus and suppressed cell growth. Conversely, restoration of SFRP1 in HepG2 hepatoma cells with truncated beta-catenin could not block the Wnt signaling pathway. Furthermore, knocking down SFRP1 by RNA interference in beta-catenin-deficient cell lines (SK-Hep1) stimulated Wnt signaling and promoted cell growth. Our data suggested that SFRP1 suppressed liver cancer cells growth through Wnt canonical signaling. Moreover, beta-catenin-independent noncanonical pathway might be involved in Wnt signaling activation through unknown molecules in HCC.

Pharmacogenomics of neuroimmune interactions in human psychiatric disorders

There is bidirectional communication between the brain and the immune system. Overproduction of interleukin-1beta (IL-1beta) leads to systemic inflammatory response syndrome (SIRS). The crucial role of IL-1beta in inflammation has been highlighted by studies performed in caspase-1 knockout mice (casp1(-/-)), transgenic mice that lack mature IL-1beta and survive lethal doses of lypopolysaccharide (LPS). We have previously shown that IL-1beta, its receptor IL-1 receptor I (IL-1RI) and caspase-1 are expressed within the brain. Moreover, we documented that peripherally injected LPS triggers a specific spatiotemporal pattern of expression of IL-1beta mRNA within the brain, suggesting that IL-1beta could be a major regulator of the central inflammatory cascade. Therefore, we studied brain transcriptional patterns that occur during LPS-induced SIRS in wild-type and casp1(-/-) mice. We showed patterns of gene expression in wild-type and casp1(-/-) mice that included differential expression of several genes, such as those for cytokines, chemokines, nitric oxide synthase 2 and cyclo-oygenase 2. A key component of the neuroimmune-endocrine axis that is increased by IL-1beta is corticotrophin releasing hormone (CRH). We found increased response to antidepressants in patients homozygous for the GAG haplotype of CRH receptor-1. Our results support the hypotheses that the CRH receptor-1 gene and possibly other genes in stress-inflammatory pathways are involved in the response to antidepressant treatment. Since dysregulation of the neuroimmune-endocrine axis appears to be one of the fundamental biological mechanisms that underlie psychiatric disorders, our findings might contribute to increase the understanding of the molecular pathways that are altered in these diseases.

P-glycoprotein mediates celecoxib-induced apoptosis in multiple drug-resistant cell lines

In several neoplastic diseases, including hepatocellular carcinoma, the expression of P-glycoprotein and cyclooxygenase-2 (COX-2) are often increased and involved in drug resistance and poor prognosis. P-glycoprotein, in addition to drug resistance, blocks cytochrome c release, preventing apoptosis in tumor cells. Because COX-2 induces P-glycoprotein expression, we evaluated the effect of celecoxib, a specific inhibitor of COX-2 activity, on P-glycoprotein-mediated resistance to apoptosis in cell lines expressing multidrug resistant (MDR) phenotype. Experiments were done using MDR-positive and parental cell lines at basal conditions and after exposure to 10 or 50 micromol/L celecoxib. We found that 10 micromol/L celecoxib reduced P-glycoprotein, Bcl-x(L), and Bcl-2 expression, and induced translocation of Bax from cytosol to mitochondria and cytochrome c release into cytosol in MDR-positive hepatocellular carcinoma cells. This causes the activation of caspase-3 and increases the number of cells going into apoptosis. No effect was shown on parental drug-sensitive or on MDR-positive hepatocellular carcinoma cells after transfection with MDR1 small interfering RNA. Interestingly, although inhibiting COX-2 activity, 50 micromol/L celecoxib weakly increased the expression of COX-2 and P-glycoprotein and did not alter Bcl-x(L) and Bcl-2 expression. In conclusion, these results show that relatively low concentrations of celecoxib induce cell apoptosis in MDR cell lines. This effect is mediated by P-glycoprotein and suggests that the efficacy of celecoxib in the treatment of different types of cancer may depend on celecoxib concentration and P-glycoprotein expression.

Specific COX-2 inhibitor, meloxicam, suppresses proliferation and induces apoptosis in human HepG2 hepatocellular carcinoma cells

BACKGROUND AND AIMS

Cyclooxygenase-2 (COX-2) is associated with carcinogenesis. The aim of this study was to investigate the expression of COX-2 in four hepatocellular carcinoma (HCC) cell lines, and evaluate the effect of a selective COX-2 inhibitor, meloxicam, in HepG2, a high COX-2 expressing cell line.

METHODS

Expression of COX-2 was detected using RT-PCR, Western blotting and immunohistochemical analysis. Cell proliferation was measured using MTT assay. Cell cycle distribution was determined by flow cytometry. Apoptosis was detected with TUNEL method. Expression of proliferating cell nuclear antigen (PCNA), cell cycle regulatory proteins including cyclins A, B1, D1 and E, and apoptosis-related proteins including Fas, Fas ligand and Bcl-2 were examined using Western blotting.

RESULTS

Cyclooxygenase-2 was intensely expressed in HepG2, HLE and BEL7402 cells, but weakly expressed in SMMC-7402 cells. Meloxicam suppressed proliferation of HepG2 cells in a dose- and time-dependent manner, resulting in cell cycle arrest in S phase and cell accumulation in G0/G1 phase. Expression of PCNA, cyclin A but not cyclin B1, cyclin D1 or cyclin E was down-regulated by meloxicam. Meloxicam also induced apoptosis of HepG2 cells, with increased expression of Fas ligand, but the expression of Fas and Bcl-2 was not affected by meloxicam treatment.

CONCLUSIONS

The present study demonstrates that the specific COX-2 inhibitor meloxicam suppresses proliferation and induces apoptosis in HCC cells that express COX-2, suggesting that COX-2 inhibition may offer a novel chemopreventive and therapeutic approach for HCC.

Promoter methylation of the secreted frizzled-related protein 1 gene SFRP1 is frequent in hepatocellular carcinoma

BACKGROUND

The secreted frizzled-related protein 1 gene (SFRP1) encodes a Wnt/beta-catenin signaling antagonist and frequently is inactivated by promoter methylation in many tumors. However, the role of SFRP1 in hepatocellular carcinoma (HCC) is not clear. Therefore, the authors investigated whether methylation of the SFRP1 promoter is common in HCC and whether it may influence SFRP1 expression.

METHODS

Four HCC cell lines, 54 HCCs, 42 cirrhotic livers, 21 livers with chronic hepatitis, and 15 normal control tissues were analyzed for 1) SFRP1 promoter methylation by using methylation-specific polymerase chain reaction analysis and bisulfite sequencing, 2) SFRP1 messenger RNA expression by using quantitative reverse transcriptase-polymerase chain reaction analysis, and 3) loss of heterozygosity (LOH) by using microsatellite markers flanking the SFRP1 locus. HCC cells were treated with the demethylating agent 5-aza-2'-deoxycytidine to determine whether it could restore SFRP1 expression.

RESULTS

SFRP1 promoter methylation was observed in 75%, 48.2%, 21.4%, 14.3% and 0% in HCC cell lines, primary HCCs, cirrhotic livers, livers with chronic hepatitis, and normal control tissues, respectively. Methylation of the SFRP1 promoter region in HCCs increased significantly compared with control tissues. All samples with SFRP1 methylation showed down-regulation of SFRP1 expression. Demethylation treatment with 5-aza-2'-deoxycytidine in HCC cells restored SFRP1 expression. Moreover, LOH of markers D8S505 and D8S1722 was found in 25% and 27.6% of the informative samples, respectively.

CONCLUSIONS

The current results suggested that promoter hypermethylation of SFRP1 is a common event in HCC and plays an important role in the regulation of SFRP1 expression. In addition to methylation-mediated down-regulation of SFRP1, LOH also may play a role.

Cyclo-oxygenase 2 expression impairs serum-withdrawal-induced apoptosis in liver cells

We have investigated the mechanism of COX-2 (cyclo-oxygenase 2)-dependent inhibition of apoptosis in liver, a key pathway underlying proliferative actions of COX-2 in liver cancers, cirrhosis, chronic hepatitis C infection and regeneration after partial hepatectomy. Stable expression of COX-2 in CHL (Chang liver) cells induced proliferation, with an increase in the proportion of cells in S-phase, but no other significant changes in cell-cycle distribution. This was associated with a marked inhibition of the apoptotic response to serum deprivation, an effect mimicked by treating empty-vector-transfected control cells (CHL-V cells) with prostaglandin E2 and prevented in COX-2-expressing cells (CHL-C cells) treated with selective inhibitors of COX-2. Serum-deprived CHL-V cells displayed several indicators of activation of intrinsic apoptosis: caspases 9 and 3 activated within 6 h and caspase 8 within 18 h, Bax expression was induced, cytochrome c was released to the cytosol, and PARP-1 [poly(ADP-ribose) polymerase 1] cleavage was evident in nuclei. COX-2 expression blocked these events, concomitant with reduced expression of p53 and promotion of Akt phosphorylation, the latter indicating activation of survival pathways. CHL cells were resistant to stimulation of the extrinsic pathway with anti-Fas antibody. Moreover, in vivo expression of GFP (green fluorescent protein)-labelled COX-2 in mice by hydrodynamics-based transient transfection conferred resistance to caspase 3 activation and apoptosis induced by stimulation of Fas.

Hepatocellular carcinoma pathogenesis: from genes to environment

Hepatocellular carcinoma is among the most lethal and prevalent cancers in the human population. Despite its significance, there is only an elemental understanding of the molecular, cellular and environmental mechanisms that drive disease pathogenesis, and there are only limited therapeutic options, many with negligible clinical benefit. This Review summarizes the current state of knowledge of this, the most common and dreaded liver neoplasm, and highlights the principal challenges and scientific opportunities that are relevant to controlling this accelerating global health crisis.

Infrequent COX-2 expression due to promoter hypermethylation in gastric cancers in Dalian, China

Cyclooxygenase-2 (COX-2) has been shown to play oncogenic roles during stepwise gastrocarcinogenesis, and its expression is correlated with Helicobacter pylori infection, tumor necrosis factor alpha-mediated nuclear factor (NF)-kappaB activation, and Wnt signaling. To examine COX-2 expression and the status of its regulatory factors, we examined 49 gastric cancers (GCs), 21 premalignant tissues, and 10 noncancerous gastric mucosa from residents of Dalian, China. Unexpectedly, it was found that COX-2 expression was infrequent in the gastric samples (18.8%, 15/80) regardless of the type of lesion or morphological phenotype. H pylori infection was detected in 19 of 35 tested GC cases. Tumor necrosis factor alpha expression, NF-kappaB nuclear translocation, or Wnt2 overexpression was observed in 56 (82.3%) of 68, 40 (50.0%) of 80, and 62 (77.5%) of 80 of the gastric tissue samples, respectively. Methylation-sensitive restriction enzyme digestion followed by polymerase chain reaction of COX-2 promoter regions revealed a remarkably high hypermethylation rate (100%, 20/20) among the COX-2-negative GCs, which was associated with the overexpression of DNA methyltransferase (DNMT) 1 (r = 0.587, P < .01). These results indicate that (1) in contrast to previous findings using other GC sources, our results show that COX-2 activity may not be a critical molecular event during GC formation, (2) the tumor-promoting effects of H pylori infection and Wnt and NF-kappaB activities may be mediated by COX-2-independent pathways, and (3) promoter hypermethylation is the major cause of COX-2 silencing in Dalian GCs, apparently because of increased expression of DNMTs (especially DNMT1). Consequently, a COX-2-oriented preventive or therapeutic strategy is not practical for Dalian GCs. The frequent COX-2 hypermethylation observed in Dalian GCs could have insightful epigenetic and epidemiologic implications.

Cyclooxygenase-2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer related mortality worldwide. The incidence of HCC is rising worldwide, especially in the United States. The overall survival of patients with HCC is grim and currently no efficient secondary prevention or systemic treatments are available. Recent evidence suggests that COX-2 signaling is implicated in hepatocarcinogenesis and COX-2 inhibitors prevent HCC cell growth in vitro and in animal models. However, given the recently reported side effect associated with some of the COX-2 inhibitors, it is imperative to develop chemotherapeutic strategy that simultaneously targets COX-2 and other related key molecules in hepatocarcinogenesis or to utilize agents inhibiting COX-2 signaling in conjunction with other standard chemotherapy or radiation therapy. Such combinational therapeutic approaches are expected to provide synergistic anti-tumor effect with lesser side effect. In this regard, the recently delineated interplay between COX-2-derived PG signaling and other growth-regulatory pathways such as EGFR, Met, iNOS, VEGF and n-3 polyunsaturated fatty acids is expected to provide important therapeutic implications. This review summarizes the recent advances in understanding the mechanisms for COX-2-derived PG signaling in hepatocarcinogenesis and focuses on the newly unveiled interactions between PG cascade and other key signaling pathways that coordinately regulate HCC growth. Understanding these mechanisms and interplays will facilitate the development of more effective chemopreventive and therapeutic strategies.

Stimulation of hepatocyte survival and suppression of CCl4-induced liver injury by the adenovirally introduced C/EBPbeta gene

Gene therapy has attracted attention as a potentially effective alternative to liver transplantation for the treatment of hepatic failure. We chose the C/EBPbeta gene, which plays vital roles in liver regeneration, as a candidate for gene therapy, and examined its effect on hepatocyte survival and the suppression of liver inflammation. C/EBPbeta gene overexpression significantly maintained hepatocyte viability during 12 days of the culture. Urea synthesis ability, which is a liver-specific function, in Adv-C/EBPbeta-infected hepatocytes was stably maintained during the culture, but the activity per cell was significantly lower than that in non-infected cells. On the contrary, DNA synthesis activity in Adv-C/EBPbeta-infected hepatocytes was significantly higher than that in non-infected cells. COX-2 was induced in Adv-C/EBPbeta-infected hepatocytes, and the addition of NS398, a specific inhibitor of COX-2, suppressed the viability-maintenance effect. COX-2 was thus shown to be involved in the survival effect of C/EBPbeta gene. The introduction of the C/EBPbeta gene into liver-damaged mice significantly suppressed the serum AST and ALT activities. These results indicate that C/EBPbeta appears to be a survival factor under stressful conditions, and the introduction of the gene has therapeutic function against liver injury.

Alcohol in hepatocellular cancer

Hepatocellular cancer accounts for almost half a million cancer deaths a year, with an escalating incidence in the Western world. Alcohol has long been recognized as a major risk factor for cancer of the liver and of other organs including oropharynx, larynx, esophagus, and possibly the breast and colon. There is compelling epidemiologic data confirming the increased risk of cancer associated with alcohol consumption, which is supported by animal experiments. Cancer of the liver associated with alcohol usually occurs in the setting of cirrhosis. Alcohol may act as a cocarcinogen, and has strong synergistic effects with other carcinogens including hepatitis B and C, aflatoxin, vinyl chloride, obesity, and diabetes mellitus. Acetaldehyde, the main metabolite of alcohol, causes hepatocellular injury, and is an important factor in causing increased oxidant stress, which damages DNA. Alcohol affects nutrition and vitamin metabolism, causing abnormalities of DNA methylation. Abnormalities of DNA methylation, a key pathway of epigenetic gene control, lead to cancer. Other nutritional and metabolic effects, for example on vitamin A metabolism, also play a key role in hepatocarcinogenesis. Alcohol enhances the effects of environmental carcinogens directly and by contributing to nutritional deficiency and impairing immunological tumor surveillance. This review summarizes the epidemiologic evidence for the role of alcohol in hepatocellular cancer, and discusses the mechanisms involved in the promotion of cancer.