Induction of plasma protein secretion in a newly established human hepatoma cell line. Mol Cell Biol. 1983;3:1133-1137. [PMID: 6683778 DOI: 10.1128/mcb.3.6.1133]

Ultrastructural Features of Gold Nanoparticles Interaction with HepG2 and HEK293 Cells in Monolayer and Spheroids

Use of multicellular spheroids in studies of nanoparticles (NPs) has increased in the last decade, however details of NPs interaction with spheroids are poorly known. We synthesized AuNPs (12.0 ± 0.1 nm in diameter, transmission electron microscopy (TEM data) and covered them with bovine serum albumin (BSA) and polyethyleneimine (PEI). Values of hydrodynamic diameter were 17.4 ± 0.4; 35.9 ± 0.5 and ±125.9 ± 2.8 nm for AuNPs, AuBSA-NPs and AuPEI-NPs, and Z-potential (net charge) values were −33.6 ± 2.0; −35.7 ± 1.8 and 39.9 ± 1.3 mV, respectively. Spheroids of human hepatocarcinoma (HepG2) and human embryo kidney (HEK293) cells (Corning ® spheroid microplates CLS4515-5EA), and monolayers of these cell lines were incubated with all NPs for 15 min–4 h, and fixed in 4% paraformaldehyde solution. Samples were examined using transmission and scanning electron microscopy. HepG2 and HEK2893 spheroids showed tissue-specific features and contacted with culture medium by basal plasma membrane of the cells. HepG2 cells both in monolayer and spheroids did not uptake of the AuNPs, while AuBSA-NPs and AuPEI-NPs readily penetrated these cells. All studied NPs penetrated HEK293 cells in both monolayer and spheroids. Thus, two different cell cultures maintained a type of the interaction with NPs in monolayer and spheroid forms, which not depended on NPs Z-potential and size.

Exploring the Mechanism of Flaccidoxide-13-Acetate in Suppressing Cell Metastasis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common liver or hepatic cancer, accounting for 80% of all cases. The majority of this cancer mortality is due to metastases, rather than orthotopic tumors. Therefore, the inhibition of tumor metastasis is widely recognized as the key strategy for successful intervention. A cembrane-type diterpene, flaccidoxide-13-acetate, isolated from marine soft coral Sinularia gibberosa, has been reported to have inhibitory effects against RT4 and T24 human bladder cancer invasion and cell migration. In this study, we investigated its suppression effects on tumor growth and metastasis of human HCC, conducting Boyden chamber and Transwell assays using HA22T and HepG2 human HCC cell lines to evaluate invasion and cell migration. We utilized gelatin zymography to determine the enzyme activities of matrix metalloproteinases MMP-2 and MMP-9. We also analyzed the expression levels of MMP-2 and MMP-9. Additionally, assays of tissue inhibitors of metalloproteinase-1/2 (TIMP-1/2), the focal adhesion kinase (FAK)/phosphatidylinositide-3 kinases (PI3K)/Akt/mammalian target of the rapamycin (mTOR) signaling pathway, and the epithelial-mesenchymal transition (EMT) process were performed. We observed that flaccidoxide-13-acetate could potentially inhibit HCC cell migration and invasion. We postulated that, by inhibiting the FAK/PI3K/Akt/mTOR signaling pathway, MMP-2 and MMP-9 expressions were suppressed, resulting in HCC cell metastasis. Flaccidoxide-13-acetate was found to inhibit EMT in HA22T and HepG2 HCC cells. Our study results suggested the potential of flaccidoxide-13-acetate as a chemotherapeutic candidate; however, its clinical application for the management of HCC in humans requires further research.

Simultaneous activation and inhibition of autophagy sensitizes cancer cells to chemotherapy

While combined chemotherapy (CT) with an autophagy inducer and an autophagy inhibitor appears paradoxical, it may provide a more effective perturbation of autophagy pathways. We used two dissimilar cell lines to test the hypothesis that autophagy is the common denominator of cell fate after CT. HA22T cells are characterized by CT-induced apoptosis and use autophagy to prevent cell death, while Huh7.5.1 cells exhibit sustained autophagic morphology after CT. Combined CT and rapamycin treatment resulted in a better combination index (CI) in Huh7.5.1 cells than combined CT and chloroquine, while the reverse was true in HA22T cells. The combination of 3 drugs (triplet drug treatment) had the best CI. After triplet drug treatment, HA22T cells switched from protective autophagy to mitochondrial membrane permeabilization and endoplasmic reticulum stress response-induced apoptosis, while Huh7.5.1 cells intensified autophagic lethality. Most importantly, both cell lines showed activation of Akt after CT, while the triplet combination blocked Akt activation through inhibition of phospholipid lipase D activity. This novel finding warrants further investigation as a broad chemosensitization strategy.

A 4-Phenoxyphenol Derivative Exerts Inhibitory Effects on Human Hepatocellular Carcinoma Cells through Regulating Autophagy and Apoptosis Accompanied by Downregulating α-Tubulin Expression

Hepatocellular carcinoma (HCC) is a leading cancer worldwide. Advanced HCCs are usually resistant to anticancer drugs, causing unsatisfactory chemotherapy outcomes. In this study, we showed that a 4-phenoxyphenol derivative, 4-[4-(4-hydroxyphenoxy)phenoxy]phenol (4-HPPP), exerts an inhibitory activity against two HCC cell lines, Huh7 and Ha22T. We further investigated the anti-HCC activities of 4-HPPP, including anti-proliferation and induction of apoptosis. Our results showed that higher dosage of 4-HPPP downregulates the expression of α-tubulin and causes nuclear enlargement in both the Huh-7 and Ha22T cell lines. Interestingly, the colony formation results showed a discrepancy in the inhibitory effect of 4-HPPP on HCC and rat liver epithelial Clone 9 cells, suggesting the selective cytotoxicity of 4-HPPP toward HCC cells. Furthermore, the cell proliferation and apoptosis assay results illustrated the differences between the two HCC cell lines. The results of cellular proliferation assays, including trypan blue exclusion and colony formation, revealed that 4-HPPP inhibits the growth of Huh7 cells, but exerts less cytotoxicity in Ha22T cells. Furthermore, the annexin V assay performed for detecting the apoptosis showed similar results. Western blotting results showed 4-HPPP caused the increase of pro-apoptotic factors including cleaved caspase-3, Bid and Bax in HCC cells, especially in Huh-7. Furthermore, an increase of autophagy-associated protein microtubule-associated protein-1 light chain-3B (LC3B)-II and the decrease of Beclin-1 and p62/SQSTM1 were observed following 4-HPPP treatment. Additionally, the level of γH2A histone family, member X (γH₂AX), an endogenous DNA damage biomarker, was dramatically increased in Huh7 cells after 4-HPPP treatment, suggesting the involvement of DNA damage pathway in 4-HPPP-induced apoptosis. On the contrary, the western blotting results showed that treatment up-regulates pro-survival proteins, including the phosphorylation of protein kinase B (Akt) and the level of survivin on Ha22T cells, which may confer a resistance toward 4-HPPP. Notably, the blockade of extracellular signal-regulated kinases (ERK), but not Akt, enhanced the cytotoxicity of 4-HPPP against Ha22T cells, indicating the pro-survival role of ERK in 4-HPPP-induced anti-HCC effect. Our present work suggests that selective anti-HCC activity of 4-HPPP acts through induction of DNA damage. Accordingly, the combination of ERK inhibitor may significantly enhance the anti-cancer effect of 4-HPPP for those HCC cells which overexpress ERK in the future.

Proteomic Characterization of Annexin l (ANX1) and Heat Shock Protein 27 (HSP27) as Biomarkers for Invasive Hepatocellular Carcinoma Cells

To search for reliable biomarkers and drug targets for management of hepatocellular carcinoma (HCC), we performed a global proteomic analysis of a pair of HCC cell lines with distinct differentiation statuses using 2-DE coupled with MALDI-TOF MS. In total, 106 and 55 proteins were successfully identified from the total cell lysate and the cytosolic, nuclear and membrane fractions in well-differentiated (HepG2) and poorly differentiated (SK-Hep–1) HCC clonal variants, respectively. Among these proteins, nine spots corresponding to proteins differentially expressed between HCC cell types were selected and confirmed by immunofluorescence staining and western blotting. Notably, Annexin 1 (ANX1), ANX–2, vimentin and stress-associated proteins, such as GRP78, HSP75, HSC–70, protein disulfide isomerase (PDI), and heat shock protein–27 (HSP27), were exclusively up-regulated in SK-Hep–1 cells. Elevated levels of ANX–4 and antioxidant/metabolic enzymes, such as MnSOD, peroxiredoxin, NADP-dependent isocitrate dehydrogenase, α-enolase and UDP-glucose dehydrogenase, were observed in HepG2 cells. We functionally demonstrated that ANX1 and HSP27 were abundantly overexpressed only in highly invasive types of HCC cells, such as Mahlavu and SK-Hep–1. Knockdown of ANX1 or HSP27 in HCC cells resulted in a severe reduction in cell migration. The in-vitro observations of ANX1 and HSP27 expressions in HCC sample was demonstrated by immunohistochemical stains performed on HCC tissue microarrays. Poorly differentiated HCC tended to have stronger ANX1 and HSP27 expressions than well-differentiated or moderately differentiated HCC. Collectively, our findings suggest that ANX1 and HSP27 are two novel biomarkers for predicting invasive HCC phenotypes and could serve as potential treatment targets.

Isoform-specific transcriptional activity of overlapping target genes that respond to thyroid hormone receptors alpha1 and beta1

Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that control multiple aspects of physiology and development. TRs are expressed in vertebrates as a series of distinct isoforms that exert distinct biological roles. We wished to determine whether the two most widely expressed isoforms, TR alpha 1 and TR beta 1, exert their different biological effects by regulating different sets of target genes. Using stably transformed HepG2 cells and a microarray analysis, we were able to demonstrate that TR alpha 1 and TR beta 1 regulate a largely overlapping repertoire of target genes in response to T(3) hormone. However, these two isoforms display very different transcriptional properties on each individual target gene, ranging from a much greater T(3)-mediated regulation by TR alpha 1 than by TR beta 1, to near equal regulation by both isoforms. We also identified TR alpha 1 and TR beta 1 target genes that were regulated by these receptors in a hormone-independent fashion. We suggest that it is this gene-specific, isoform-specific amplitude of transcriptional regulation that is the likely basis for the appearance and maintenance of TR alpha 1 and TR beta 1 over evolutionary time. In essence, TR alpha 1 and TR beta 1 adjust the magnitude of the transcriptional response at different target genes to different levels; by altering the ratio of these isoforms in different tissues or at different developmental times, the intensity of T(3) response can be individually tailored to different physiological and developmental requirements.

Characterization of the 5' regulatory region of the human Glycine N-methyltransferase gene

Glycine N-methyltransferase (GNMT) is a tumor susceptibility gene for both hepatocellular carcinoma and prostate cancer. We have previously characterized GNMT genomic structure and mapped its chromosomal localization to 6p12. For this study we identified a GNMT transcriptional start site at the 14th position upstream of the ATG codon. Electrophoretic mobility shift assay results indicate binding of the nuclear factor-Y (NF-Y) transcription factor to the CCAAT box (-71/-67) of the GNMT gene. Mutation assay results suggest that the nucleotide sequence in the -56/-47 region is a binding site for a putative transcriptional factor. The TATA-less core promoter (-133/+14) contains three major elements: an Sp1 site, CCAAT box, and a novel box within the CTGTCGGCTG sequence. One functional xenobiotic response element (XRE) located at the -104/-82 region is inducable by benzo[a]pyrene treatment. We believe our results have value for the study of GNMT transcriptional regulation.

Thyroid hormone promotes cell invasion through activation of furin expression in human hepatoma cell lines

The objective of this study was to identify genes regulated by thyroid hormone (T(3)) and associated with tumor invasion. The gene encoding furin, as previously identified by cDNA microarray, is known to be up-regulated by T(3) treatment, and stimulated furin production occurs in thyroidectomized rats after administration of T(3). Presently, by using serial deletion of the promoter and EMSAs, the T(3) response element on the furin promoter was localized to the -6317/-6302 region. T(3)-mediated furin up-regulation was cooperative with TGF-beta because T(3) induction increased after Smad3/4 addition. Furthermore, the invasiveness of HepG2-thyroid hormone receptor (TR) cells was significantly increased by T(3) treatment, perhaps due to furin processing of matrix metalloproteinase-2 and -9. In addition, furin up-regulation either by stable overexpression or T(3) and/or TGF-beta induction was evident in severe-combined immune-deficient mice inoculated with HepG2-TRalpha1 cells. The HepG2-furin mice displayed a higher metastasis index and tumor size than HepG2-neo mice. Notably, the increased liver and lung tumor number or size in the hyperthyroid severe-combined immune-deficient mice as well as TGF-beta mice was attributed specifically to furin overexpression in the HepG2-TRalpha1 cells. Furthermore, this study demonstrated that furin overexpression in some types of hepatocellular carcinomas is TR dependent and might play a crucial role in the development of hepatocellular carcinoma. Thus, T(3) regulates furin gene expression via a novel mechanism or in cooperation with TGF-beta to enhance tumor metastasis in vitro and in vivo.

Decreased expression of UK114 is related to the differentiation status of human hepatocellular carcinoma

Previous studies have identified that the expression of UK114 is tissue specific and the protein has been found to be most abundant in liver and kidney. However, the expression of UK114 in human hepatocellular carcinoma and its relationship to differentiation and transformation of hepatocellular carcinoma have not been studied. In this study, the expression of UK114 in human hepatocellular carcinoma was examined by Northern and Western blot analyses. We found that UK114 was significantly down-regulated in most of hepatocellular carcinoma tissues compared with adjacent nontumor tissues (72.7%) at both mRNA and protein levels. We looked into the possibility that this decreased expression of UK114 in the hepatocellular carcinoma tissues may play a role in the differentiation or tumorigenicity of hepatocellular carcinoma. Immunohistochemical staining showed that the reduced expression of UK114 in hepatocellular carcinoma tissues was correlated with the tumor differentiation status as graded by the Edmondson-Steiner classification. On the other hand, overexpression of UK114 was not able to suppress the proliferation of human hepatoma cells and tumorigenicity in nude mice. These results suggest that UK114 does not seem to act as a tumor suppressor gene; however, it may useful as a biomarker that will assist in the grading of the differentiation status of hepatocellular carcinoma samples.

Reduction of PKC alpha decreases cell proliferation, migration, and invasion of human malignant hepatocellular carcinoma

Protein kinase C (PKC) superfamily play key regulatory roles on the development of cancer. However, the exact role of these enzymes in human hepatocellular carcinoma (HCC) has not been well established. Using the RT-PCR and Western blotting to analyze the levels of PKC isoforms mRNA and protein in the five different differentiated hepatoma cell lines, we found that PKC alpha was highly expressed in the poor-differentiated HCC cell lines (SK-Hep-1 and HA22T/VGH) as compared with that in the well-differentiated HCC cell lines (PLC/PRF/5, Hep3B, and HepG2). When treated with PKC alpha antisense oligonucleotides (ODN), both HA22T/VGH and SK-Hep-1 cells lines showed the reduction of PKC alpha expression, as well as a deceleration in the growth rate and in the level of cyclin D1, but the increase in the levels of p53 and p21(WAF1/CIP1). Moreover, the reduction of PKC alpha expression also inhibited the migratory and invasive potential of both HA22T/VGH and SK-Hep-1 cells lines, and revealed a down-regulation of several migration/invasion-related genes (MMP-1, u-PA, u-PAR, and FAK). These phenomenon were also confirmed by DNA-based small interfering RNA (siRNA) PKC alpha and PKC alpha/beta specific inhibitor Go6976. Thus, the results indicated that PKC alpha may be associated with regulation of cell proliferation/migration/invasion in human poorly differentiated HCC cells, suggesting a role for the PKC alpha in the malignant progression of human HCC.

PKCalpha expression regulated by Elk-1 and MZF-1 in human HCC cells

Our previous study found that PKCalpha was highly expressed in the poor-differentiated human HCC cells and associated with cell migration and invasion. In this study, we further investigated the gene regulation of this enzyme. We showed that PKCalpha expression enhancement in the poor-differentiated human HCC cells was found neither by DNA amplification nor by increasing mRNA stability using differential PCR and mRNA decay assays. After screening seven transcription factors in the putative cis-acting regulatory elements of human PKCalpha promoters, only Elk-1 and MZF-1 antisense oligonucleotide showed a significant reduction in the PKCalpha mRNA level. They also reduced cell proliferation, cell migratory and invasive capabilities, and DNA binding activities in the PKCalpha promoter region. Over-expression assay confirmed that the PKCalpha expression may be modulated by these two factors at the transcriptional level. Therefore, these results may provide a novel mechanism for PKCalpha expression regulation in human HCC cells.

Colchicine sensitizes human hepatocellular carcinoma cells to damages caused by radiation

AIM: We studied the effect of colchicine combined with radiation on the survival of human hepatocellular carcinoma (HCC) HA22T/VGH cells.

METHODS: Twenty-four hours after treatment with 0-8 ng/mL colchicine, HA22T/VGH cells were irradiated at various doses (0, 1, 2, 4, and 8 Gy). Colony assay was performed to assess the surviving cell fraction. Survival curves were fitted by using a linear-quadratic model to estimate the sensitizer enhancement ratio (SER). Flow cytometry was used for cell cycle analysis.

RESULTS: Colchicine at lower concentrations (1 and 2 ng/mL) had obvious synergy with radiation to inhibit HCC cell growth, whereas higher concentrations (4 and 8 ng/mL) had only additive effect to radiation. Pretreatment with 1 and 2 ng/mL colchicine for 24-h enhanced cell killing by radiation with SERs of 1.21 and 1.53, respectively. G₂/M arrest was only observed with higher colchicine doses (8 and 16 ng/mL) after 24-h treatment; this effect was neither seen with lower doses (1, 2, and 4 ng/mL) nor with any dose after only 1 h of treatment.

CONCLUSION: Our results suggest that colchicine has potential as an adjunct to radiotherapy for HCC treatment. Lower doses of colchicine possess radiosensitizing effects via some mechanism other than G₂/M arrest. Further study is necessary to elucidate the mechanism.

IL-4 suppresses the expression and the replication of hepatitis B virus in the hepatocellular carcinoma cell line Hep3B

IL-4 has been known as a Th2 cytokine and can act on B cells, T cells, and monocytes. In this study we demonstrate that IL-4Rs are expressed on human hepatocellular carcinoma (HCC) cells. We found that IL-4 suppresses hepatitis B surface Ag (HBsAg) mRNA and HBsAg production in the Hep3B cell line, which contains an integrated hepatitis B virus (HBV) genome and constitutively secretes HBsAg. When Hep3B cells are further transfected with the plasmid pHBV3.6 that contains >1 U of HBV genome, IL-4 could suppress the production of all HBV RNA and secreted HBsAg and hepatitis B virus e Ag. Furthermore, an endogenous DNA polymerase activity assay shows a decrease in HBV DNA after IL-4 treatment. Using luciferase reporter assays we have demonstrated that IL-4 could suppress the activity of the surface promoter II and the core promotor (CP). To delineate how IL-4 suppressed the transcription of HBV genes, we have examined the effect of IL-4 on the expression of transcription factors that are known to bind to the core upstream regulatory sequence, which colocalizes with enhancer II of the HBV genome. Our results demonstrate that IL-4 suppresses the expression of C/EBPalpha. Furthermore, overexpression of C/EBPalpha blocked 43 and 30% of the IL-4-mediated suppression of CP activity and IL-4-induced suppression of pregenomic RNA, respectively. Finally, we have demonstrated that mutations affecting the C/EBPalpha-binding sites on core upstream regulatory sequence/enhancer II completely abolish the IL-4-mediated suppression of CP activity. Thus, down-regulation of C/EBPalpha may be involved in the anti-HBV effect of IL-4 in Hep3B cells.

Moscatilin from the orchid Dendrobrium loddigesii is a potential anticancer agent

The Dendrobrium species have been commonly used in traditional Chinese medicine as a tonic to nourish the stomach, replenish body fluid, and reduce fever. However, their application as possible therapeutic agents for the treatment of cancers has not been examined. In this study, we want to examine the efficacy of using moscatilin, a natural antiplatelet agent extracted from the stems of Dendrobrium loddigesii, as an anticancer agent. Our results have shown that moscatilin exerts potent cytotoxic effect against cancer cell lines derived from different tissue origins, including those from the placenta, stomach, and lung, but not those from the liver. In addition, we have found that the mechanism of action of moscatilin may be related to its ability to induce a G2 phase arrest in responsive cells. However, unlike some G2 arresting agents, moscatilin has no detectable inhibitory effect on cyclin B-cdc-2 kinase activity. Thus, the precise nature of its cytotoxic mechanism remains to be determined. Our results in this study imply that moscatilin is potentially efficacious for chemoprevention and/or chemotherapy against some types of cancer.

Characterization of reduced expression of glycine N-methyltransferase in cancerous hepatic tissues using two newly developed monoclonal antibodies

Glycine N-methyltransferase (GNMT) is a protein with multiple functions. Recently, two Italian siblings who had hepatomegaly and chronic elevation of serum transaminases were diagnosed to have GNMT deficiency caused by inherited compound heterozygosity of the GNMT gene with missence mutations. To evaluate the expression of GNMT in cell lines and tissues from hepatocellular carcinoma (HCC) patients, we produced two monoclonal antibodies (mAbs) 4-17 and 14-1 using two recombinant GNMT fusion proteins. M13 phage peptide display showed that the reactive epitopes of mAbs 4-17 and 14-1 were amino acid residues 11-15 and 272-276 of human GNMT, respectively. The dissociation constants of the binding between GNMT and mAbs were 1.7 x 10(-8) M for mAb 4-17 and 1.8 x 10(-9) M for mAb 14-1. Both mAbs can identify GNMT present in normal human and mouse liver tissues using Western blotting (WB) and immunohistochemical staining assay (IHC). In addition, WB with both mAbs showed that none of 2 hepatoblastoma and 5 HCC cell lines expressed GNMT. IHC demonstrated that 50% (13/26) of nontumorous liver tissues and 96% (24/25) of HCC tissues did not express GNMT. Therefore, the expression of GNMT was downregulated in human HCC.

Effects of soy isoflavones on apoptosis induction and G2-M arrest in human hepatoma cells involvement of caspase-3 activation, Bcl-2 and Bcl-XL downregulation, and Cdc2 kinase activity

Genistein, biochanin-A, and daidzein, the predominant soy isoflavones, have been reported to lower the risk of cancer, but it is not known whether they protect against human hepatoma cancer. This study was designed to investigate their effects on cell growth, the cell cycle, and apoptosis induction in the human hepatoma cell lines, HepG2, Hep3B, Huh7, PLC, and HA22T. Genistein, biochanin-A, and daidzein inhibited growth of all five lines in a dose-dependent manner. DNA fragmentation studies and the TUNEL assay demonstrated that isoflavones caused tumor cell death by induction of apoptosis. Activation of caspase-3 and cleavage of the caspase-3 substrate, poly(ADP-ribose)polymerase, was seen in hepatoma cells after 24 hours' exposure to isoflavones. In addition, isoflavone cytotoxicity correlated with downregulation of Bcl-2 and Bcl-XL expression. Synergistic effects of the three isoflavones were observed on cell growth inhibition, apoptosis induction, and anti-apoptotic protein expression. Flow cytometry showed that genistein, but not biochanin-A or daidzein, induced progressive and sustained accumulation of hepatoma cancer cells in the G2/M phase as a result of inhibition of Cdc2 kinase activity. Coapplication of caffeine prevented this cell cycle arrest, but not apoptosis, showing that cell cycle arrest was not necessary for apoptosis. Furthermore, the isoflavones combination also had a significant tumor-suppressive effect in nude mice. These results suggest that isoflavones might be promising agents for the treatment of human hepatoma.

Effect of nordihydroguaiaretic acid on intracellular Ca(2+) concentrations in hepatocytes

The effect of nordihydroguaiaretic acid (NDGA) on Ca(2+) signaling in human hepatoma cells (HA22/VGH) has been investigated. NDGA (5-50 microM) increased [Ca(2+)](i) concentration-dependently. The [Ca(2+)](i) increase comprised an initial rise and an elevated phase over a time period of 4 min. Removal of extracellular Ca(2+) reduced 10-50 microM NDGA induced [Ca(2+)](i) signals by 45+/-5%. Consistently, the 50 microM NDGA-induced [Ca(2+)](i) increase in Ca(2+)-containing medium was reduced by 41+/-2% by 10 microM of La(3+), nifedipine or verapamil. In Ca(2+)-free medium, pretreatment with 20 microM NDGA for 6 min abolished the [Ca(2+)](i) increase induced by the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (1 microM). Conversely, 20 microM NDGA failed to increase [Ca(2+)](i) after 1 microM thapsigargin had depleted the endoplasmic reticulum Ca(2+) store. Inhibition of phospholipase C with 2 microM U73122 had little effect on 20 microM NDGA-induced Ca(2+) release. Several other lipoxygenase inhibitors had no effect on basal [Ca(2+)](i). Together, the data suggest that NDGA increased [Ca(2+)](i) in hepatocytes in a lipoxygenase-independent manner, by releasing Ca(2+) from the endoplasmic reticulum and causing Ca(2+) influx.

Metastatic human hepatocellular carcinoma models in nude mice and cell line with metastatic potential

Metastatic human HCC model is needed for the studies on mechanism and interven tion of metastatic recurrence. By using orthotopic implantation of histologically intact tissues of 30 surgical specimens, a patient-like metastatic model of hu man HCC in nude mice (LCI-D20) and a low metastatic model of human HCC in nude mice (LCI-D35) have been established. All mice with transplanted LCI-D20 tumors exhibited extremely high metastatic ability including spontaneous metasta sis to liver, lungs, lymph nodes and peritoneal seeding. Remarkable difference was also found in expression of some of the invasiveness related genes and growth factors between the LCI-D20 and LCI-D35 tumors. PAI-1 increased gradually following tumor progression in LCI-D20 model, and correlated with tumor size and AFP level. Phasic expression of tissue intercellular adhesio nmolecule-1 in this model was also observed. Using corneal micropocket model, it was demonstrated that the vascular response induced by LCI-D20 tumor was stronger than that induced by LCI-D35 tumor. Similar report on metastatic human HCC model in nude mice and human HCC cell line with metastatic potential was rarely found in the literature. This LCI-D20 model has been widely used for the studies on intervention of metastasis, including anti-angiogenesis, antisense approach, metallopro teinase inhibitor, differentiation inducer, etc. It is concluded that the establ ishment of metastatic human HCC model in nude mice and human HCC cell line with metastatic potential will provide important models for the in vivo and in vitro study of HCC invasiveness, angiogenesis as well as intervention of HCC recurrence.

Establishment of cell clones with different metastatic potential from the metastatic hepatocellular carcinoma cell line MHCC97

AIM: To establish clone cells with different metastatic potential for the study of metastasis-related mechanisms.

METHODS: Cloning procedure was performed on parental hepatocellular carcinoma (HCC) cell line MHCC97, and biological characteristics of the target clones selected by in vivo screening were studied.

RESULTS: Two clones with high (MHCC97-H) and low (MHCC97-L) metastatic potential were isolated from the parent cell line. Compared with MHCC97-L, MHCC97-H had smaller cell size (average cell diameter 43 μm vs 50 μm) and faster in vitro and in vivo growth rate (tumor cell doubling time was 34.2 h vs 60.0 h). The main ranges of chromosomes were 55-58 in MHCC97-H and 57-62 in MHCC97-L. Boyden chamber in vitro invasion assay demonstrated that the number of penetrating cells through the artificial basement membrane was (37.5 ± 11.0) cells/field for MHCC97-H vs (17.7 ± 6.3)/field for MHCC97-L. The proportions of cells in G0-G1 phase, S phase, and G2-M phase for MHCC97-H/MHCC97-L were 0.56/0.65, 0.28/0.25 and 0.16/0.10, respectively, as measured by flow cytometry. The serum AFP levels in nude mice 5 wk after orthotopic implantation of tumor tissue were (246 ± 66) μg•L¯¹ for MHCC97-H and (91 ± 66) μg•L¯¹ for MHCC97-L. The pulmonary metastatic rate was 100% (10/10) vs 40% (4/10).

CONCLUSION: Two clones of the same genetic background but with different biological behaviors were established, which could be valuable models for investigation on HCC metastasis.

Differentiation status modulates transcription factor NF-kappaB activity in unstimulated human hepatocellular carcinoma cell lines

We report herein a novel finding that under an unstimulated condition, a group of four human hepatocellular carcinoma (HCC) cell lines with varying degrees of differentiation, can spontaneously activate NF-KB. The propensity of activation coincided inversely with the differentiation status, with order being SK-Hep-1 > J5 > Hep3B > HepG2. Further studies indicate that this pattern of activation correlates excellently with the descending order of intracellular GSH/GSSG ratios as well as with the ascending order in the ability of these cells to generate hydrogen peroxide. Taken together, our data suggest that differentiation status may play a pivotal role in modulating intracellular thiol redox status and the extent of catalase expression, which may be crucial in the control of NF-kappaB activity in these HCC cells.

Human glucose-6-phosphate dehydrogenase (G6PD) gene transforms NIH 3T3 cells and induces tumors in nude mice

The main physiological function of glucose-6-phosphate dehydrogenase (G6PD) is to produce NADPH and ribose 5-phosphate, which are essential for reductive biosynthesis and nucleic acid synthesis. In normal cells, G6PD expression is tightly controlled; however, in many tumors, regulation of its expression is altered, resulting in a significant increase in G6PD activity. To investigate the potential role of G6PD in tumorigenesis, we transfected NIH 3T3 cells with human G6PD cDNA. Cells overexpressing G6PD showed altered cell morphology and exhibited tumorigenic properties. In contrast to the control cells or cells transfected with mutated G6PD cDNA, G6PD-overexpressing cells were not contact inhibited and exhibited anchorage-independent growth. They divided more quickly and induced rapidly growing, large fibrosarcomas in nude mice. Moreover, the induced tumorigenic properties were positively correlated with the level of G6PD activity. Interestingly, treatment with buthionine SR-sulfoximine (BSO), a glutathione depletion agent, decreased the colony-forming efficiency of G6PD-overexpressing cells in soft agar, which implicates that alteration of the redox balance may be involved in G6PD-induced tumorigenesis. A comparative analysis of the expression level of G6PD in a variety of human cancer cell lines was also performed. Northern- and Western-blot analyses revealed that G6PD was particularly overexpressed in human esophageal cancer cell lines. Our observations indicate that G6PD may act as a potential oncogene, whose overexpression plays a critical role in neoplastic transformation.

Targeting of aminopeptidase N to bile canaliculi correlates with secretory activities of the developing canalicular domain

We have used human hepatoma cell lines as an in vitro model to study the development of hepatic bile canaliculi (BC). Well-differentiated hepatoma cells cultured for 72 hours could develop characteristic spheroid structures at sites of cell-cell contact that contained tight junctions and various membrane protein markers, resembling BC found in vivo. Intact cytoskeleton was essential for this differentiation process. In the coculture experiments in which cells of different origins were populated together, BC only formed between hepatic cells and preferentially among well-differentiated cells. Poorly differentiated hepatoma cells never formed BC among themselves, but could be induced to undergo canalicular differentiation by interacting with well-differentiated cells. During BC morphogenesis, integral canalicular membrane proteins were gradually delivered and accumulated at the developing BC. Among them, targeting of aminopeptidase N (APN) seemed to correlate with activation of certain secretory functions. Specifically, only APN-positive BC supported excretion of fluorescein diacetate (FDA) and 70-kd dextran, but had no relationship with secretion of horseradish peroxidase (HRP). Targeting of another BC protein, dipeptidyl peptidase IV (DPPIV), on the other hand, bore no association with any secretory activity examined. In addition, inhibition of enzymatic activity of APN could perturb canalicular differentiation without affecting cell proliferation. Our results suggest that targeting of APN proteins may reflect or even play an important role in the development and functional maturation of the canalicular structures.

Cordyceps sinensis increases the expression of major histocompatibility complex class II antigens on human hepatoma cell line HA22T/VGH cells

Previous studies suggest that down-regulation of the major histocompatibility complex (MHC) antigens on the cell surface of certain tumors results in an escape of immune surveillance. Cordyceps sinensis is well known for its modulatory effect on host immune system. To investigate the modulatory effect of Cordyceps sinensis on MHC class II antigen expression on hepatoma cells, immunostaining with monoclonal antibody (MAb) L243, against the HLA DR region of MHC class II antigens on human hepatoma cell line HA22T/VGH was analyzed by using flow cytofluorimetry. The degree of fluorescence intensity on L243(+) cells was expressed as relative mean fluorescence intensity (RMFI). The extract of Cordyceps sinensis (VGH-CS-ME-82, 40 micrograms/ml) was found to increase the MHC class II antigen expression on HA22T/VGH cells with the percentage of L243(+) cells 40.2 +/- 2.5 and RMFI 6.6 +/- 0.4; whereas cells without treatment disclosed the percentage of L243(+) cells 17.2 +/- 1.4 and RMFI 5.4 +/- 0.3, respectively (p < 0.05). There was a dose-related increase in the degree of fluorescence intensity in terms of RMFI on VGH-CS-ME-82 induced cells. The RMFI in cells treated with IFN-gamma 0, 0.2 and 5 ng/ml were 5.4 +/- 0.3, 8.2 +/- 0.4, and 24.9 +/- 1.5, respectively; whereas the RMFI in cells co-incubated with VGH-CS-ME-82 (40 micrograms/ml) and IFN-gamma 0, 0.2 ng/ml and 5 ng/ml were 6.7 +/- 0.2 (p < 0.05), 9.2 +/- 0.9 (p < 0.1) and 29.5 +/- 1.2 (p < 0.005), respectively. We conclude that VGH-CS-ME-82, either alone or with IFN-gamma induction, increases the MHC class II antigen expression on hepatoma cell line HA22T/VGH, which will shed light into the present immunotherapy, and make the host immune surveillance more effective against tumor cells with down-regulated MHC class II antigen expression.

Parallel hybridization analysis of multiple protein kinase genes: identification of gene expression patterns characteristic of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the major causes of human cancer deaths worldwide. To identify alterations of the genetic program associated with human HCC, we designed a new protocol based on the high-density replica method to analyze protein kinase gene expression in normal liver, HCC, and HCC-derived cell lines. RNA was prepared for reverse transcription and cDNA was used for PCR amplification of the conserved catalytic domain of protein kinase genes. Initially, from a pair of HCC and the adjacent noncancerous tissues, we sequenced 228 samples and identified 26 genes that represent different tyrosine kinase subfamilies. High-density grid filters were then prepared to assist the identification, by hybridization, of genes that are differentially expressed in normal vs HCC samples. Eleven tyrosine kinase genes were tested, and positive signals were reliably scored by doubly offset duplicates and by two independent gene-specific probes. Of the 11 genes tested, PDGF receptor-beta, MEKK-3, axl, and FGFR-4 are preferentially expressed in tumor samples. Additionally, we analyzed protein kinase gene expression in five HCC cell lines and identified distinct kinase gene expression patterns in different cell lines. Our results suggest that multiple kinases are activated in different tumors and confirm that there is molecular heterogeneity in the mechanisms sustaining autonomous cell growth in liver tumor formation.

Characterization of glycine-N-methyltransferase-gene expression in human hepatocellular carcinoma

Messenger RNA differential display was used to study liver-gene expression in paired tumor and non-tumor tissues from hepatocellular carcinoma (HCC) patients. mRNA differential display and Northern-blot analyses showed that a 0.8-kb cDNA fragment was diminished or absent from the tumorous tissues of 7 HCC patients. The cDNA fragment was sequenced and found to have 98.7% nucleotide sequence homology with human glycine-N-methyltransferase cDNA (GNMT). In addition, there was no detectable level of GNMT expression in 4 human HCC cell lines, SK-Hep1, Hep 3B, HuH-7 and HA22T, examined by Northern-blot assay. A full-length GNMT cDNA clone-9-1-2 was obtained by screening a Taiwanese liver cDNA library. In comparison with the GNMT cDNA sequence reported elsewhere, clone 9-1-2 had 4 nucleotide differences resulting in 1 amino-acid change. Immunohistochemical staining with rabbit anti-recombinant GNMT serum showed that GNMT protein almost completely disappeared in liver-cancer cells, while it was abundant in the non-tumorous liver cells. Down-regulation of GNMT gene expression may be involved in the pathogenesis of liver cancer.

Secretory production of bioactive recombinant human granulocyte-macrophage colony-stimulating factor by a baculovirus expression system

The proliferation and differentiation of hematopoietic cells are stimulated by a group of glycoproteins called colony stimulating factors (CSFs). Previously, we found that the human hepatoma cell line HA22T/VGH secreted a high level of human granulocyte-macrophage colony-stimulating factor (hGM-CSF). The cDNA of hGM-CSF, including the signal peptide sequence, was amplified from the total RNA of HA22T/VGH by a reverse-transcription polymerase chain reaction and was cloned into the pUC18 vector. After confirming the nucleotide sequence, the cDNA was inserted into a pVL1393 baculovirus transfer vector. The recombinant baculovirus carrying hGM-CSF cDNA was generated by co-transfecting the hGM-CSF recombinant transfer vector and BaculoGold baculovirus DNA into the Sf9 insect cells. The expected hGM-CSF transcript was detected in the recombinant virus-infected Sf9 cells. The conditioned media of the infected cells were analyzed by a slot-blot immunoassay. The results indicate that the infected insect cells produced and secreted hGM-CSF. According to colony forming assay, a maximum titer of 2.1 x 10(6). U ml-1 of hGM-CSF in the medium was obtained on the third day after infection.

Cytokine regulation of HIV-1 LTR transactivation in human hepatocellular carcinoma cell lines

Human hepatocellular carcinoma (HCC) cell lines, HEP-G2, J5, and SK-HEP-1, which differ in their differentiation status, were compared for their trans-activating activities after treatment with cytokines or 12-O-tetradecanoylphorbol-13-acetate (TPA). These cells were transfected with a long terminal repeat (LTR) which was derived from human immunodeficiency virus type 1 (HIV-1) and ligated to chloramphenicol acetyl transferase (CAT) gene. After treatment with interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), interferon-gamma (IFN-gamma), or TPA, they exhibited various degrees of enhancement of transactivation. The well differentiated HEP-G2 cells exhibited the highest degree of enhancement with these agents, while the poorly differentiated SK-HEP-1 cells showed no enhancement with cytokines and slight enhancement with TPA. The J5 cells, which were intermediate in their status of differentiation, showed a moderate degree of enhancement with cytokines and TPA. These results suggest that HCC cells at different stages of differentiation may produce different levels of cellular transacting factors activated by each of these agents. To map the cytokine response elements (CREs) in the HIV-1-LTR, HEP-G2 cells were transfected with nested series of 5' deletion mutants of HIV-1-LTR and treated with each of these cytokines. It was found that not only the degrees but also the patterns of enhancement varied depending upon the presence of positive or negative regulatory sequences in HIV-1-LTR, and that the NF-kappa B sequence played an important role, either by itself or in conjunction with the 5'-proximal response elements (REs) to interact with cellular trans-activating factors elicited by the cascade of transduction responses to cytokines. Despite the presence of promoters including kappa B and IFN-gamma RE as well as IL-6RE sequence in HIV-1-LTR-transfected cells, the poorly differentiated SK-HEP-1 cells showed no enhancement of transactivation by these cytokines, suggesting the lack of receptors or activity of some signal transduction factors which are present in well differentiated HEP-G2 and moderately differentiated J5 cells.

Detection of a novel lactate dehydrogenase isozyme and an apparent differentiation-associated shift in isozyme profile in hepatoma cell lines

A hitherto unreported lactate dehydrogenase (LD) isoenzyme, which migrates electrophoretically to the relative position between LD2 and LD3 has been identified in the electropheratogram in 7 of 7 (100%) cultured hepatoma cell lines with various degrees of differentiation and is thus given the name LD2-3. LD2-3 seems to be specific for hepatoma cells because this atypical isoenzyme can not be detected in other tumor cell lines. In addition, the hepatoma cell lines also show a distinct pattern of LD isoenzyme and the isoenzyme pattern varies with the degree of differentiation. Hence, the expression pattern of LD isoenzyme phenotypes may provide a good marker for the investigation of human hepatoma cell differentiation.

Stimulation of proliferation by 3,3',5-triiodo-L-thyronine in poorly differentiated human hepatocarcinoma cells overexpressing beta 1 thyroid hormone receptor

To understand the role of thyroid hormone nuclear receptors (TRs) in hepatocarcinogenesis, we characterized the TRs in nine human hepatocarcinoma cell lines. The expression of TR proteins is receptor subtype- and cell type-dependent. TR alpha 1 protein expresses similarly at a low level in each of the nine cell lines. In contrast, TR beta 1 is overexpressed in hepatocarcinoma cells which are poorly differentiated. Furthermore, thyroid hormone was found to stimulate the proliferation of cells in which TR beta 1 is overexpressed. These results suggest that TR beta 1 is most likely involved in the differentiation and proliferation of hepatocarcinoma cells. Our studies have shed new light in the understanding of the role of TRs in liver carcinogenesis.

Differentiated liver cell specificity of the second enhancer of hepatitis B virus

Hepatitis B virus is a hepatotropic virus. Its replication and gene expression are mainly restricted to hepatocytes in the infective process. The viral gene expression thus provides a unique system with which to study the control of tissue-specific gene expression. We have previously reported the identification and characterization of the second enhancer (enhancer II) of hepatitis B virus. In this report, we further demonstrate that the minimal functional constituents of the second enhancer, box alpha and box beta, display liver cell and differentiation state specificity. Moreover, box alpha exhibits the same liver cell and differentiation state specificity when functioning as an upstream regulator for the basal core promoter. Gel shift experiments reveal a unique box alpha-binding protein, protein a, which is present only in differentiated liver cells, where enhancer II is functional. The converse is true for another box alpha-binding protein, protein f, which is present only in poorly differentiated liver cells and nonliver cells. The simplest hypothesis that explains these results is that protein a activates and/or protein f suppresses the enhancer and upstream regulator functions. Although C/EBP is a candidate for a transcription factor that interacts with box alpha or box beta, none of the binding factors identified in the gel shift assays, including protein a and protein f, is likely to be C/EBP because they differ from C/EBP in heat lability and sequence preference.

Characterization and nucleotide sequences of the variable regions of a monoclonal antibody against alpha-fetoprotein

alpha-Fetoprotein (AFP) is a well-known tumor marker of hepatocellular carcinoma (HCC). Monoclonal antibodies against AFP possessing specific binding ability to HCC are potential candidates for immunoscintigraphy and immunotherapy. A new monoclonal antibody against AFP (0325-6-9) was isolated. Its specificity and targeting tumor ability were characterized by enzyme-linked immunosorbent assay (ELISA), cell immunostain and complement killing. These results suggest that 0325-6-9 is specific to hepatoma cells. The nucleotide sequences of variable regions of 0325-6-9 were determined by M13 dideoxynucleotide sequencing method. With the information of nucleotide sequence, this antibody then could be modified by recombinant technology for its usage in in vivo diagnosis and immunotherapy.

The formation of bile canaliculi in human hepatoma cell lines

Hepatocytes, known as polarized epithelial cells, are composed of sinusoid, basolateral and bile canalicular domains. Each domain contains proteins specific for it. Our studies indicate that the well-differentiated human hepatoma cell lines HepG2 and HuH-7 formed bile canaliculi in tissue culture, whereas the poorly differentiated hepatoma cell lines HA22T/VGH and SK-HEP-1 did not. We also used the 9B2 monoclonal antibody, previously shown to be specific for the human bile canalicular domain, to study formation of bile canaliculi in these human hepatoma cell lines. All four cell lines synthesize the 140-kD 9B2 antigen. Studies using peroxidase-antiperoxidase staining and immunoelectron microscopy revealed that the 9B2 antigen was first detected in cytoplasm and packaged in microvilli-lined vesicles, then vectorially transported to the cell surface and eventually fused with microvilli-lined vesicles from neighboring cells to form bile canaliculi in well-differentiated hepatoma cell lines. However, the 9B2 antigen of poorly differentiated lines was synthesized in cytoplasm, then transported directly to and evenly distributed on the cell membrane. These results lead us to conclude that human hepatoma cell lines could serve as a good in vitro model to study the formation of bile canaliculi in human hepatocytes. The bile canaliculi of human hepatocytes may be preformed and assembled in the intracellular, microvilli-lined vesicles, then vectorially transported to the cell surface, where they form the bile canaliculi through vesicles fusion. Finally, formation of bile canaliculi and transport of 9B2 antigen may be related to the differentiation of hepatocytes or progression stages of human hepatoma cells.

Expression of high- and low-affinity epidermal growth factor receptors in human hepatoma cell lines

Data are presented from a comparative research on expression of epidermal growth factor (EGF) receptors and response to EGF of six independently established cell lines derived from human hepatoma. These lines differ in terms of the degree of differentiation, presence of hepatitis B virus (HBV) DNA copies in integrated form and expression of HBV genes. Our results indicate differential expression of membrane EGF receptors and differential response to EGF under serum- and hormone-free culture conditions. Furthermore, a significant difference in affinity could be detected between EGF receptors of the two highly dedifferentiated cell lines (HA22T/VGH and Li7A) whose replication is inhibited by EGF concentrations capable of stimulating more differentiated phenotypes.

The surface gene promoter of the human hepatitis B virus displays a preference for differentiated hepatocytes

By transfections of hepatitis B virus (HBV) DNA into five human hepatoma cell lines with the characteristics of differentiated human hepatocytes, three human hepatoma cell lines possessing partial hepatocyte-associated markers, and one non-liver cell line, we demonstrated that the expression of hepatitis B surface and core genes preferentially occurred in hepatoma cell lines with differentiated hepatocyte-associated characteristics. With a heterologous CAT gene as a reporter, the transcriptional activity of the promoter region containing both the distal (SPI) and the proximal (SPII) promoters of hepatitis B surface gene was found to show a preference for differentiated hepatoma cell lines. The SPI promoter which produces a RNA transcript for the synthesis of the large surface protein shows a strong preference, at least 750-fold, for differentiated hepatoma cells, while the SPII promoter which produces RNA transcripts for the synthesis of the middle and major surface proteins shows a moderate preference, about 20- to 59-fold. Further study indicates that this 750-fold preference of the SPI transcriptional activity for differentiated hepatoma cell lines can be attributed to the regulatory sequences of both the SPI and the HBV enhancer regions. These results also imply the important role of the large surface protein of HBV on the hepatocyte-specific infectivity of this virus.

Natural and activated cytotoxic lymphocytes reactivity to human hepatocellular carcinoma cell lines in hepatocellular carcinoma patients

The status of cellular cytotoxic activity in Hepatocellular Carcinoma (HCC) patients was compared to that in normal individuals by testing the cytotoxicity against K562 and five established HCC cell line targets. Natural killer (NK) activity of fresh peripheral blood mononuclear (PBM) cells in HCC patients to K562 cell line target was lower than that in normal donors. NK activity of unstimulated PBM cells from either source was minute against all five HCC cell line targets. Three different activation systems were employed to examine the cellular cytotoxicity of activated PBM cells: (1) conventional mixed lymphocyte culture (MLC), (2) allogeneic mixed lymphocyte tumor culture (MLTC), and (3) lymphokine-activated killer (LAK) cell culture. The cytotoxic effects of PBM cells in all three activation conditions were significantly lower in HCC patients than in normal donors (P less than 0.05 to P less than 0.01). These results suggest that, in addition to naturally present NK cells, the degree of in vitro activation of PBM cells may also have decreased in HCC patients.

Nuclear antigens reacted with sera and ascites of hepatocellular carcinoma patients

In order to study hepatocellular carcinoma-associated antigens, screening of sera and ascites was done from hepatocellular carcinoma patients having antibodies reactive with three hepatocellular carcinoma cell lines (PLC/PRF/5, Hep 3B and HA22T/VGH). The indirect immunofluorescent antibody test was used. Ten of 86 (11.6%) sera and 3 of 14 (21.4%) ascites from hepatocellular carcinoma patients showed positive bindings, whereas only 1 of 35 (2.8%) sera, none of 4 (0%) ascites from chronic hepatitis patients and 3 of 60 (5%) normal human sera had positive immunofluorescent antibody activity. The binding specificities of these positive specimens were further defined by other human cancer cell lines and mouse NIH/3T3 fibroblasts. The antinuclear antibody test against mouse liver sections was also performed. The results suggested that antigens identified by the two tests may not be identical. The nature of nuclear antigens reactive with one of the serum samples, S83, and ascites A83 were characterized. These antigens were sensitive to trypsin but not to RNase A and DNase I. Further studies by radioimmunoprecipitation and two-dimensional gel electrophoresis with serum S83 and ascites A83 showed two acidic phosphorylated antigens with molecular weights of 77 and 79 kd, which had a pI around pH 5.2. The presence of a large amount of these two phosphorylated proteins in 5 of 7 human hepatocellular carcinoma cell lines suggests that these two antigens might play some roles in the carcinogenesis or progression of human hepatocellular carcinoma.

Regulation of hepatitis B virus S gene promoter in transfected cell lines

Hepatitis B virus (HBV) contains an enhancer element that activates the viral core and X gene promoters. To investigate the transcriptional regulation of the viral S gene promoter, we transfected SK-Hep1 cells with circularized forms of HBV DNAs and their enhancerless mutants. We have found that expression of the S gene, determined by measurement of the appearance of HBsAg in the media and by RNA analysis, is to a large extent enhancer-dependent. This observation was further confirmed by analysis of a series of plasmids containing the chloramphenicol acetyl-transferase (CAT) gene under the control of the S gene promoter and the HBV enhancer element. Interestingly, in contrast to its behavior in SK-Hep1 cells, the S gene promoter is highly active in Alexander cells, in the absence of the enhancer element. This implies that activity of the S gene promoter is cell-type specific.

Differential response of the human hepatoma-derived cell line HA22T/VGH to polypeptide mitogens

Several human cell lines derived from primary cancer of the liver are able to grow under serum-free conditions and produce spreading and growth factors which are released into the culture medium. Since this autocrine growth under hormone-free conditions might play a basic role in malignant transformation, we studied the effect on cell replication and the presence of specific membrane receptors of epidermal growth factor (EGF) and insulin on a dedifferentiated human hepatoma cell line, named HA22T/VGH. Our results point to a similar inhibitory effect on cell replication in the presence of both EGF and insulin, in spite of detecting different affinities of binding.

Karyotypic characterization of an established human hepatoma cell line HA22T/VGH

The karyotype of an established human hepatoma cell line HA22T/VGH was characterized by G-banding. A majority of the 200 cells counted had around 70 chromosomes at passage 24, and 60 at passage 338. Of the 50 cells karyotyped from each of passage 24 and passages 338-339, chromosomes #13 and #18 were absent. The presence of the Y chromosome was reduced dramatically from a mean value of 1.12/cell at passage 24 to 0.12/cell at passages 338-339. In general, most of the chromosomes--particularly chromosomes #5, #7, #9, #15, and #21--tended to be less represented in the course of propagation in vitro. The presence of multiple copies of a normal chromosome in a single cell was quite common for chromosomes #5 and #7 at both early and late passages. Numerous structural rearrangements of the chromosomes were observed.

Genomic clones of the human liver-type phosphofructokinase

Genomic clones of human liver phosphofructokinase (PFK) were isolated by screening a gene bank enriched for chromosome 21 sequences with two synthetic oligonucleotide probes designed from peptide sequences of purified human liver PFK. A 3.3 Kb fragment derived from the genomic clones was sub-cloned and designated to pG-PFKL 3.3. It hybridized with a 3.5 Kb mRNA on Northern blots and was able to enrich selectively for liver PFK mRNA by hybrid-selection. These results demonstrated that the isolated clones contain sequences homologous to human PFKL mRNA. When hybridized to genomic DNA blots pG-PFKL 3.3 reacted with the same 3.3 Kb BamHI fragment in both human DNA and DNA of the mouse/human hybrid line WA17 which contains human chromosome 21 as the only human chromosome. These data confirm the assignment of the PFKL gene to chromosome 21.

Monoclonal antibodies against antigens expressed on human hepatocellular carcinoma cells

Monoclonal antibodies with selectivity for human hepatoma cell lines were produced by immunizing BALB/c mice with human hepatoma cell lines, HA22T/VGH or Hep 3B, and fusing sensitized mouse spleen cells with mouse myeloma cells. Two monoclonal antibodies recognizing antigens present only on human hepatoma cell lines were investigated. The monoclonal antibody IB1 was found to react with 3 of 9 hepatoma cell lines. Monoclonal antibody 9B2 reacted with all nine hepatoma cell lines. None of the other 20 cell lines tested was bound by IB1 and 9B2. The immunoperoxidase staining of monoclonal antibodies on frozen sections of paired hepatoma and normal liver tissues from the same individuals were studied. Antibody IB1 reacted with 3 of 13 hepatoma tissues, but with none of the normal liver and other tissues, and antibody 9B2 was reactive with antigens appearing on the bile canalicular domain of hepatoma and normal liver tissues. The antibody 9B2 stained no normal tissues with the exception of proximal tubules of kidney. Radioimmunoprecipitation tests identified two antigens reacting with 9B2. The major antigen had an apparent molecular weight of 140,000 and a minor one of 130,000. Therefore, antibody IB1 seems to be specific for antigens present on a group of human hepatoma cells and may be useful for classification and diagnosis of human hepatomas. Antibody 9B2 is quite specific to human liver cells and may be used to provide clues for the characterization of tumor cell lines, identification of metastatic tumors with hepatocytic origin, and study of the structure and function of bile canaliculi.

Hepatocellular carcinoma after thorotrast exposure: establishment of a new cell line (Mz-Hep-1)

A human hepatoma cell line, associated with thorotrast exposure, from an hepatitis B marker-negative patient was established as a permanent cell line (Mz-Hep-1) in tissue culture. Histology of the primary tumor, as well as phase contrast, transmission and scanning electron microscopy of the cultured cells showed typical characteristics of liver cells. Mz-Hep-1 cells secreted complement components (C2, C3, C4), carcinoembryonic antigen, lactate dehydrogenase, chymotrypsin, haptoglobin and retinol-binding protein and expressed HLA-, transferrin-, blood group B-related determinants and complement component C5 and carcinoembryonic antigen on their cell surface. Mz-Hep-1 cells represent the first human hepatoma cell line, which is strongly associated with a carcinogen.