prostaglandin-d2 and Liver-Neoplasms

Microsomal prostaglandin E synthase 1 (mPGES-1) is the terminal regulator of PGE₂ synthesis. The expression of mPGES-1 is increased by stimulating inflammatory factors in various human cancers. However, whether hepatitis B virus (HBV) infection affects mPGES-1 and its molecular mechanism in liver cells has not been studied. In this study, we observed that mPGES-1 expression was positively correlated with HBV X protein (HBx) in hepatocellular carcinoma cancerous tissue, and HBx enhanced the mPGES-1 promoter activity in HL7702 liver cells. Mechanistic investigations revealed that HBx can increase the early growth response 1 (EGR1) binding to the transcription site of mPGES-1 promoter. The overexpression and knockdown of EGR1 did not affect cyclooxygenase-2 (COX-2) transcription and expression in HL7702-HBx cells. We also investigated the unique function of 15-deoxy-Δ(12,14)-prostaglandin J₂ (15d-PGJ₂), a kind of PGE₂ inhibitor, in the regulation of mPGES-1 expression in HBx-positive liver cells. In the presence of 15d-PGJ₂, the expression of COX-2 was unaffected, but that of the EGR1-mPGES-1-PGE₂ axis was inhibited. Moreover, the capacity of EGR1 binding to the mPGES-1 promoter decreased, and the change in HL7702-HBx cells was more significant. The results indicated that EGR1 is a specific transcription factor in the up-regulation of mPGES-1 expression by HBx, and targeting EGR1 may contribute to inhibiting the change from inflammation to HBV-induced cancer.

Topics: Base Sequence; Binding Sites; Carcinoma, Hepatocellular; Cyclooxygenase 2; Dinoprostone; Early Growth Response Protein 1; Female; Gene Expression Regulation; Hepatitis B virus; Humans; Intramolecular Oxidoreductases; Liver Neoplasms; Male; Middle Aged; Molecular Sequence Data; Promoter Regions, Genetic; Prostaglandin D2; Prostaglandin-E Synthases; Trans-Activators; Up-Regulation; Viral Regulatory and Accessory Proteins

Emerging evidence suggests that tumor-initiating cells (TICs) are the most malignant cell subpopulation in tumors because of their resistance to chemotherapy or radiation treatment. Targeting TICs may be a key innovation for cancer treatment. In this study, we found that PPARγ agonists inhibited the cancer stem cell-like phenotype and attenuated tumor growth of human hepatocellular carcinoma (HCC) cells. Reactive oxygen species (ROS) initiated by NOX2 upregulation were partially responsible for the inhibitory effects mediated by PPARγ agonists. However, PPARγ agonist-mediated ROS production significantly activated AKT, which in turn promoted TIC survival by limiting ROS generation. Inhibition of AKT, by either pharmacological inhibitors or AKT siRNA, significantly enhanced PPARγ agonist-mediated inhibition of cell proliferation and stem cell-like properties in HCC cells. Importantly, in nude mice inoculated with HCC Huh7 cells, we demonstrated a synergistic inhibitory effect of the PPARγ agonist rosiglitazone and the AKT inhibitor triciribine on tumor growth. In conclusion, we observed a negative feedback loop between oxidative stress and AKT hyperactivation in PPARγ agonist-mediated suppressive effects on HCCs. Combinatory application of an AKT inhibitor and a PPARγ agonist may provide a new strategy for inhibition of stem cell-like properties in HCCs and treatment of liver cancer.

Topics: AC133 Antigen; Animals; Antigens, CD; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Enzyme Activation; Glycoproteins; Humans; Liver Neoplasms; Male; Membrane Glycoproteins; Mice; Mice, Nude; NADPH Oxidase 2; NADPH Oxidases; Neoplastic Stem Cells; Oxidative Stress; Peptides; Phenotype; PPAR gamma; Prostaglandin D2; Proto-Oncogene Proteins c-akt; Reactive Oxygen Species; Ribonucleosides; Rosiglitazone; Thiazolidinediones

Chronic hepatitis B virus (HBV) infection is the most common cause of hepatocellular carcinoma (HCC) worldwide. This study investigated the antineoplastic effects of intrinsic and extrinsic peroxisome proliferator-activated receptor gamma (PPARgamma) ligands against HBV-associated HCC cells in vitro. Four cell lines that were established from patients with HBV-associated HCC were used. The cells were cultured in various concentrations of the following PPARgamma ligands: troglitazone, pioglitazone, rosiglitazone and 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)). Cell proliferation, cell cycle and apoptosis were analyzed. PPARgamma was expressed in all the cell lines studied. Among the PPARgamma ligands, pioglitazone and 15d-PGJ(2) clearly inhibited the HBV-associated HCC cell growth and increased the proportion of cells in the sub-G1 phase in the cell-cycle analysis. In apoptosis assays, DNA fragments increased significantly, and the activities of caspase-3 and -9 also increased. A pan-caspase inhibitor and a caspase-3 inhibitor suppressed the PPARgamma ligand-induced apoptosis in a dose-dependent manner. These two PPARgamma ligands decreased the expression of bcl-2 in most of the cell lines studied. The results suggest that pioglitazone and 15d-PGJ(2) have antineoplastic effects on HBV-associated HCC cells. Both of these PPARgamma ligands could be candidates for cancer prevention or the chemotherapy of HBV-associated HCC.

Topics: Antineoplastic Agents; Apoptosis; Carcinoma, Hepatocellular; Caspase 3; Caspase 9; Cell Line, Tumor; Cell Proliferation; Hepatitis B virus; Humans; Hypoglycemic Agents; Immunologic Factors; Ligands; Liver Neoplasms; Pioglitazone; PPAR gamma; Prostaglandin D2; Thiazolidinediones

Peroxisome proliferator-activated receptors (PPARs) mediate the effects of various ligands, known as peroxisome proliferators, a heterogeneous class of compounds including industrial chemicals, pharmaceuticals, and biomolecules such as fatty acids and eicosanoids. Among peroxisome proliferators, fibrate derivatives are considered specific ligands for PPARα, whereas eicosanoids, such as PGJ2, for PPARγ. The study aimed to clarify the relation between PPARs and apoptosis or proliferation on the same type of cells, using clofibrate as specific ligand of PPARα and PGJ2 as specific ligand of PPARγ. The cells used were human hepatocarcinoma HepG2 cells. The results showed that PPARα protein content increased in HepG2 cells treated with clofibrate, causing apoptosis in a time- and concentration-dependent way, as evidenced by the citofluorimetric assay and determination of BAD, myc and protein phosphatase 2A protein content. It also emerged that PPARγ increased in the same cells when treated with a specific ligand of this PPAR; in this case the increase of PPARγ did not cause an increase of apoptosis, but a time- and concentration-dependent inhibition of cell proliferation, evidenced by decreased cell numbers and increased number of cells in the G0/G1 phase of the cycle. It may be concluded that PPARα is chiefly related to apoptosis and PPARγ to cell proliferation.

Topics: Apoptosis; bcl-Associated Death Protein; Carcinoma, Hepatocellular; Cell Cycle; Cell Proliferation; Clofibrate; Hep G2 Cells; Humans; Ligands; Liver Neoplasms; Osmolar Concentration; PPAR alpha; PPAR gamma; Prostaglandin D2; Protein Phosphatase 2; Proto-Oncogene Proteins c-myc; Signal Transduction; Time Factors

To investigate the effect of 15-deoxy-Delta(12,14)-prostaglandin J(2) (15-d-PGJ(2)) on the anoikis of hepatocellular carcinoma (HC) cells and mechanisms thereof.. Fibronectin or polyhydroxyethyl methacrylate (poly-HEMA) were coated onto tissue culture plates, cell growth status and morphological changes were detected by optical microscope. DNA fragmentation analysis and Flow cytometry were used to measure cell apoptotic activity. Western blotting analysis was performed to detect the levels of focal adhesion kinase (FAK) and phosphorylated FAK(p-FAK). Furthermore, small interfering RNA (siRNA) was used to suppress FAK expression.. The adhesion rate of the BEL-7402 cells treated with 15-d-PGJ(2) began to decrease 12 h after the treatment, time- and dose-dependently compared with the HC cell control group (all P < 0.05); when the concentration of 15-d-PGJ2 was 20 micromol/L, the adherent cells ratio at 24 h and 48 h later were (66.0 +/- 3.6)% and (35.0 +/- 5.0)% respectively. Anoikis of BEL-7402 cells was observed by flow cytometry and DNA fragmentation analysis. Western blotting showed that the p-FAK level of the BEL-7402 cells treated with 15-d-PGJ2 for 24 h decreased dose-dependently, however, the total FAK protein did not change.. 15-d-PGJ(2) induces anoikis and decreases the phosphorylated FAK expression of the hepatocellular carcinoma cells.

Topics: Anoikis; Apoptosis; Blotting, Western; Carcinoma, Hepatocellular; Cell Line, Tumor; Dose-Response Relationship, Drug; Flow Cytometry; Focal Adhesion Protein-Tyrosine Kinases; Humans; Liver Neoplasms; Phosphorylation; Prostaglandin D2; RNA, Small Interfering; Transfection

The peroxisome proliferator-activated receptor-gamma (PPARgamma) high-affinity ligand, 15-deoxy-Delta-12,14-PGJ(2) (15d-PGJ(2)), is toxic to malignant cells through cell cycle arrest and apoptosis induction. In this study, we investigated the effects of 15d-PGJ(2) on apoptosis induction and expression of apoptosis-related proteins in hepatocellular carcinoma (HCC) cells. 15d-PGJ(2) induced apoptosis in SK-Hep1 and HepG2 cells at a 50 micro M concentration. Pretreatment with the pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone (2-VAD-fmk), only partially blocked apoptosis induced by 40 micro M 15d-PGJ(2). This indicated that 15d-PGJ(2) induction of apoptosis was associated with a caspase-3-independent pathway. 15d-PGJ(2) also induced down-regulation of the X chromosome-linked inhibitor of apoptosis (XIAP), Bclx, and apoptotic protease-activating factor-1 in SK-Hep1 cells but not in HepG2 cells. However, 15d-PGJ(2) sensitized both HCC cell lines to TNF-related apoptosis-induced ligand-induced apoptosis. In SK-Hep1 cells, cell toxicity, nuclear factor-kappaB (NF-kappaB) suppression, and XIAP down-regulation were induced by 15d-PGJ(2) treatment under conditions in which PPARgamma was down-regulated. These results suggest that the effect of 15d-PGJ(2) was through a PPARgamma-independent mechanism. Although cell toxicity was induced when PPARgamma was down-regulated in HepG2 cells, NF-kappaB suppression and XIAP down-regulation were not induced. In conclusion, 15d-PGJ(2) induces apoptosis of HCC cell lines via caspase-dependent and -independent pathways. In SK-Hep1 cells, the ability of 15d-PGJ(2) to induce cell toxicity, NF-kappaB suppression, or XIAP down-regulation seemed to occur via a PPARgamma-independent mechanism, but in HepG2 cells, NF-kappaB suppression by 15d-PGJ(2) was dependent on PPARgamma.

Topics: Apoptosis; Apoptosis Regulatory Proteins; Blotting, Western; Carcinoma, Hepatocellular; Caspase 3; Caspases; Cell Survival; Dose-Response Relationship, Drug; Down-Regulation; Humans; Liver Neoplasms; Membrane Glycoproteins; NF-kappa B; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; TNF-Related Apoptosis-Inducing Ligand; Transcription Factors; Transfection; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

15-deoxy-delta12,14-prostaglandin J2 (15-d-PGJ2) induces apoptosis in several carcinoma cell lines and is a potent activator of peroxisome proliferators-activated receptor-gamma (PPAR-gamma). In the present study, we examined the effect of 15-d-PGJ2 on human hepatoma cells.. HuH-7 and HepG2 cell lines were used in all the experiments. The mRNA expression of PPAR-gamma was studied by reverse transcriptase-polymerase chain reaction. The cell viability was determined by a modified MTT assay. Two methods were used for the determination of apoptosis in hepatoma cells: the TUNEL assay, and detection of fragmented mono- and oligo-nucleosomes by ELISA.. The expression of PPAR-gamma mRNA and protein was detected in HuH-7 and HepG2. Treatment with 15-d-PGJ2 decreased cell viability in a time- and dose-dependent manner. 15-d-PGJ2 induced apoptosis and this effect was time-dependent. Exposure of cells to 15-d-PGJ2 induced caspase-3 and -9 activation. Furthermore, co-treatment with the pan-caspase inhibitor Z-VAD-FMK or the caspase-3 inhibitor Z-DEVD-FMK blocked apoptosis of human hepatoma cells that had been treated with 15-d-PGJ2.. Our study demonstrates that PPAR-gamma is expressed in human hepatoma cell lines and that treatment with 15-d-PGJ2 inhibits the growth of these cells by inducing apoptosis through caspase activation.

Topics: Amino Acid Chloromethyl Ketones; Apoptosis; Carcinoma, Hepatocellular; Caspase Inhibitors; Caspases; Cell Line, Tumor; Cysteine Proteinase Inhibitors; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Humans; Immunologic Factors; In Situ Nick-End Labeling; Liver Neoplasms; Oligopeptides; Prostaglandin D2; Receptors, Cytoplasmic and Nuclear; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors

We reported earlier that expression of Sox-4 was found to be elevated during prostaglandin (PG) A(2) and delta(12)-PGJ(2) induced apoptosis in human hepatocarcinoma Hep3B cells. In this study, the role of Sox-4 was examined using human Hep3B and HepG2 cell lines. Sox-4 induction by several apoptotic inducer such as A23187 (Ca(2+) ionophore) and etoposide (topoisomerase II inhibitor) and Sox-4 transfection into the cells were able to induce apoptosis as observed by the cellular DNA fragmentation. Antisense oligonucleotide of Sox-4 inhibited the induction of Sox-4 expression and blocked the formation of DNA fragmentation by PGA(2) and delta(12)-PGJ(2) in Hep3B and HepG2 cells. Sox-4-induced apoptosis was accompanied with caspase-1 activation indicating that caspase cascade was involved in this apoptotic pathway. These results indicate that Sox-4 is involved in Hep3B and HepG2 cells apoptosis as an important apoptotic mediator.

Topics: Apoptosis; Blotting, Western; Calcimycin; Caspase 1; Caspase Inhibitors; Etoposide; Gene Expression Regulation, Neoplastic; High Mobility Group Proteins; Humans; Liver Neoplasms; Oligopeptides; Prostaglandin D2; Prostaglandins A; SOXC Transcription Factors; Trans-Activators; Transfection; Tumor Cells, Cultured

Arachidonic acid metabolites known to affect platelet function also interfere with tumor growth and metastases. The purpose of this study was to evaluate the anti-metastatic potential of ketoconazole, a thromboxane synthetase and 5-lipoxygenase inhibitor, on hepatic metastasis from a human pancreatic adenocarcinoma in nude mice and its effect on serum prostaglandin levels.. The human pancreatic tumor cells (RWP-2) were injected intrasplenically in nude mice grouped into control, ketoconazole (270 microg), ketoconazole (360 microg), and ketoconazole (540 microg). The agent was administered intraperitoneally 30 min before and every 24 h after the tumor cell inoculation for 8 days. In a separate experiment thromboxane B2 (TxB2), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2) and 6-Keto-F1a (stable prostacyclin derivative) were measured on blood from controls, tumor bearing animals and animals bearing tumors treated with 270 microg of ketoconazole.. Statistically significant differences were observed between the control and three-treatment groups on the reduction of liver tumor nodules (p < 0.001), and in the liver surface areas occupied by tumor (p < 0.001). The TxB2 levels decreased from 150.6 ng/mL in the tumor bearing to 104.8 ng/mL in the ketoconazole treated animals (p < 0.05). PGD2, PGE2 and 6-keto-F1a levels increased to 7.1 ng/mL, 8.3 ng/mL, and 13.6 ng/mL from 3 ng/mL, 5.8 ng/mL, and 0.02 ng/mL respectively (p < 0.001).. These results indicate that ketoconazole significantly reduced hepatic metastases from the human pancreatic carcinoma RWP-2 in the nude mouse model, and inhibited thromboxane B2 formation, potentiating a concomitant redirection of platelet endoperoxide metabolism into PGD2, PGE2, and 6-keto-F1a. It is hypothesized that the changes in the arachidonic acid metabolism mediate the ameliorating effect of ketoconazole on experimental hepatic metastasis.

Topics: 6-Ketoprostaglandin F1 alpha; Adenocarcinoma; Animals; Antineoplastic Agents; Dinoprostone; Humans; Injections, Intraperitoneal; Ketoconazole; Liver Neoplasms; Mice; Mice, Nude; Neoplasm Metastasis; Pancreatic Neoplasms; Prostaglandin Antagonists; Prostaglandin D2; Prostaglandins; Thromboxane B2; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

The inhibitory action of prostaglandin D2 (PGD2) and its effect on the cell cycle were examined in cell lines SW480 and LS174T of human colon cancer. The growth of the cell lines were assessed 24 h and 48 h after the addition of 1.0 microgram/ml and 10.0 micrograms/ml PGD2. The growth of SW480 cells was inhibited 48 h, but not 24 h, after the addition of 1.0 microgram/ml, and 24 h and 48 h after the addition of 10.0 micrograms/ml, while that of LS174T was inhibited by both doses after 24 h and 48 h. S-Phase DNA synthesis in the SW480 cells was significantly blocked 24 h after the addition of 10.0 micrograms/ml PGD2. The cell cycle of LS174T cells was arrested at the G0 + G1 phase 24 h after the addition of 1.0 microgram/ml and 10.0 micrograms/ml PGD2. The correlation between hepatic metastasis and PGD2 concentration in human cancer tissue was examined. The mean value of PGD2 concentrations in the primary cancer tissue was significantly lower in the hepatic metastasis group than that in the group without hepatic metastasis. These findings suggest that measuring the PGD2 in cancer tissue may be useful for detecting and predicting the hepatic metastasis from human colorectal cancer.

Topics: Biomarkers, Tumor; Cell Division; Colonic Neoplasms; Dose-Response Relationship, Drug; Humans; Liver Neoplasms; Prognosis; Prostaglandin D2; Tumor Cells, Cultured

Prostaglandin (PG) A2 (PGA2) and Delta12-PGJ2 have potent antiproliferative activity on various tumor cell growths in vitro. In this study, we investigated the mechanism of PGA2/Delta12-PGJ2-mediated apoptosis, including intracellular apoptosis-related genes in human hepatocarcinoma Hep3B cells. Hep3B cells treated with PGA2/Delta12-PGJ2 showed that a time-dependent DNA fragmentation characterized by marked apoptosis and the elevation of c-myc mRNA expression. In proportion to the increased c-myc gene transcription, heat shock protein 70 (hsp70) mRNA was induced from 1 to 24 h after PGA2/Delta12-PGJ2 treatment. The transfection of c-myc antisense oligomers in Hep3B cells significantly delayed the induction of HSP70 expression and blocked formation of DNA fragmentation by PGA2/Delta12-PGJ2. Moreover, overexpressed HSP70 showed an increased resistance to apoptosis by PGA2/Delta12-PGJ2 treatment. These results demonstrated that the decreased survival in response to PGA2/Delta12-PGJ2 was causally related to the amount of c-myc and the induction of c-myc regulated the elevation of HSP70 which have been known to correlate with a resistance to apoptosis.

Topics: Antineoplastic Agents; Apoptosis; Carcinoma; Cell Division; Gene Expression Regulation; HSP70 Heat-Shock Proteins; Humans; Liver Neoplasms; Oligodeoxyribonucleotides; Prostaglandin D2; Prostaglandins; Prostaglandins A; Proto-Oncogene Proteins c-myc; Transcription, Genetic

We studied the effect of intracellular glutathione (GSH), which was known to conjugate readily with an alpha, beta-unsaturated carbonyl of 9-deoxy-delta 9,12-13,14-dihydroPGD2 (delta 12-PGJ2), on the cytotoxicity of delta 12-PGJ2. delta 12-PGJ2 caused DNA fragmentation in human hepatocellular carcinoma Hep 3B cells, which was blocked by cycloheximide (CHX). The delta 12-PGJ2-induced apoptosis was augmented by GSH depletion resulted from pretreatment with buthioninine sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase. On the contrary, N-acetyl-cysteine (NAC), a precursor of cysteine, elevated the GSH level and protected cells from initiating apoptosis by delta 12-PGJ2. Sodium arsenite, a thiol-reactive agent, also induced apoptosis, which was potentiated or attenuated by BSO or NAC treatment respectively. These results suggest that the apoptosis-inducing activity of delta 12-PGJ2 is due to thiol-reactivity and intracellular GSH modulates the delta 12-PGJ2-induced apoptosis by regulating the accessibility of delta 12-PGJ2 to target proteins containing thiol groups.

Topics: Acetylcysteine; Antineoplastic Agents; Apoptosis; Arsenites; Buthionine Sulfoximine; Carcinoma, Hepatocellular; Cell Division; Cycloheximide; DNA Fragmentation; Electrophoresis, Agar Gel; Enzyme Inhibitors; Glutathione; Humans; Liver Neoplasms; Prostaglandin D2; Sodium Compounds; Structure-Activity Relationship; Sulfhydryl Compounds; Tumor Cells, Cultured

In order to study the mechanism of cancer metastasis, AH100B cells, an ascitic hepatoma cell line, were transplanted into the small intestine of male Donryu rats. Each metastatic nodule in the liver was collected with the respective intestinal lesion. Each sample thus obtained was injected into the peritoneal cavity of male Donryu rats to make free cancer cells. Then, the cancer cells, having an intact cell surface, of the metastatic and primary intestinal lesion were collected respectively. After washing in Dolbecco's PBS (Ca2+ and Mg(2+)-free, pH 7.2), the definite numbers of cancer cells of the metastatic and primary intestinal lesion were incubated in the PBS containing [1-14C]-AA at 25 degrees C for 30 min, respectively. AA metabolites formed during the incubation period were extracted and subjected to TLC, followed by autoradiography. Each radioactive part was scraped off the plate and measured for its radioactivity. The pattern of the ability to synthesize PGs was different between the cancer cells which metastasized to the liver and those of the primary lesion, that is, percentage values of PGE2 and PGF2 alpha were higher (p < 0.01) in the cancer cells which metastasized to liver as compared with those of the primary intestinal lesion. These results suggest that PGs produced by hepatic metastatic cancer cells might play an important role in cancer metastasis.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Arachidonic Acid; Carcinoma, Hepatocellular; Cell Line; Dinoprost; Dinoprostone; Intestinal Neoplasms; Liver Neoplasms; Male; Prostaglandin D2; Prostaglandins; Rats; Rats, Inbred Strains; Thromboxane B2; Tumor Cells, Cultured

9-deoxy-delta 9,delta 12-13,14-dihydro-prostaglandin D2 (delta 12-PGJ2) is a potent inhibitor of proliferation of tumor cells. In the present study, the effect of delta 12-PGJ2 on the alpha-fetoprotein(AFP) and the albumin gene expression was analyzed in HuH-7 human hepatoma cells. delta 12-PGJ2 inhibited the cell growth and reduced the medium AFP concentrations dose-dependently. To determine whether this decline of AFP depends only on the relative decrease in cell numbers by delta 12-PGJ2, or is in part, due to the decrease in the cellular AFP synthesis by delta 12-PGJ2, Northern blot analysis was performed in this study. By Northern blotting, it was shown that delta 12-PGJ2 caused a marked reduction in the levels of the AFP mRNA and the albumin mRNA. In contrast, the level of the beta-actin mRNA was not changed by delta 12-PGJ2. In the transient chloramphnicol acetyltransferase plasmid transfection experiments, delta 12-PGJ2 did not suppress the AFP enhancer activity, which possibly regulates both the AFP and the albumin gene expression in HuH-7 hepatoma cells, but resulted in the selective repression of the AFP and the albumin promoter activity. These results suggest that delta 12-PGJ2 suppresses not only cell growth but also expression of the AFP gene and the albumin gene at the transcriptional level in human hepatoma cells.

Topics: Albumins; alpha-Fetoproteins; Blotting, Northern; Carcinoma, Hepatocellular; Cell Division; Chloramphenicol O-Acetyltransferase; Enzyme-Linked Immunosorbent Assay; Gene Expression; Humans; Liver Neoplasms; Promoter Regions, Genetic; Prostaglandin D2; RNA, Messenger; Transfection; Tumor Cells, Cultured