Differentiating effect of sodium butyrate on human hepatoma cell lines PLC/PRF/5, HCC-M and HCC-T

Gut microbial metabolite butyrate improves anticancer therapy by regulating intracellular calcium homeostasis

BACKGROUND AND AIMS

Gut microbiota are recognized to be important for anticancer therapy, yet the underlying mechanism is not clear. Here, through the analysis of clinical samples, we identify the mechanism by which the gut microbial metabolite butyrate inhibits HCC and then explore new strategies for HCC treatment.

APPROACH AND RESULTS

In our study, we demonstrate that gut microbial metabolite butyrate improves anticancer therapy efficacy by regulating intracellular calcium homeostasis. Using liquid chromatography-mass spectrometry analysis, we found that butyrate metabolism is activated in HCC patients compared with healthy individuals. Butyrate levels are lower in the plasma of HCC patients by gas chromatography-mass spectrometry (GC-MS) analysis. Butyrate supplementation or depletion of short-chain Acyl-CoA dehydrogenase (SCAD) gene (ACADS), encoding a key enzyme for butyrate metabolism, significantly inhibits HCC proliferation and metastasis. The profiling analysis of genes upregulated by butyrate supplementation or ACADS knockdown reveals that calcium signaling pathway is activated, leading to dysregulation of intracellular calcium homeostasis and production of reactive oxygen species. Butyrate supplementation improves the therapy efficacy of a tyrosine kinase inhibitor sorafenib. On the basis of these findings, we developed butyrate and sorafenib coencapsulated mPEG-PLGA-PLL nanoparticles coated with anti-GPC3 antibody (BS@PEAL-GPC3) to prolong the retention time of drugs and enhance drug targeting, leading to high anticancer efficacy. BS@PEAL-GPC3 nanoparticles significantly reduce HCC progression. In addition, BS@PEAL-GPC3 nanoparticles display excellent HCC targeting with excellent safety.

CONCLUSIONS

In conclusion, our findings provide new insight into the mechanism by which the gut microbial metabolites inhibit HCC progression, suggesting a translatable therapeutics approach to enhance the clinical targeted therapeutic efficacy.

Butyrate prevents the migration and invasion, and aerobic glycolysis in gastric cancer via inhibiting Wnt/β-catenin/c-Myc signaling

Gastric cancer (GC) remains a common cause of cancer death worldwide. Evidence has found that butyrate exhibited antitumor effects on GC cells. However, the mechanism by which butyrate regulate GC cell proliferation, migration, invasion, and aerobic glycolysis remains largely unknown. The proliferation, migration, and invasion of GC cells were tested by EdU staining, transwell assays. Additionally, protein expressions were determined by western blot assay. Next, glucose uptake, lactate production, and cellular ATP levels in GC cells were detected. Furthermore, the antitumor effects of butyrate in tumor-bearing nude mice were evaluated. We found, butyrate significantly prevented GC cell proliferation, migration, and invasion (p < .01). Additionally, butyrate markedly inhibited GC cell aerobic glycolysis, as shown by the reduced expressions of GLUT1, HK2, and LDHA (p < .01). Moreover, butyrate notably decreased nuclear β-catenin and c-Myc levels in GC cells (p < .01). Remarkably, through activating Wnt/β-catenin signaling with LiCl, the inhibitory effects of butyrate on the growth and aerobic glycolysis of GC cells were diminished (p < .01). Moreover, butyrate notably suppressed tumor volume and weight in GC cell xenograft nude mice in vivo (p < .01). Meanwhile, butyrate obviously reduced nuclear β-catenin, c-Myc, GLUT1, HK2 and LDHA levels in tumor tissues in GC cell xenograft mice (p < .01). Collectively, butyrate could suppress the growth and aerobic glycolysis of GC cells in vitro and in vivo via downregulating wnt/β-catenin/c-Myc signaling. These findings are likely to prove useful in better understanding the role of butyrate in GC.

Sodium butyrate inhibits aerobic glycolysis of hepatocellular carcinoma cells via the c‐myc/hexokinase 2 pathway

Aerobic glycolysis is a well‐known hallmark of hepatocellular carcinoma (HCC). Hence, targeting the key enzymes of this pathway is considered a novel approach to HCC treatment. The effects of sodium butyrate (NaBu), a sodium salt of the short‐chain fatty acid butyrate, on aerobic glycolysis in HCC cells and the underlying mechanism are unknown. In the present study, data obtained from cell lines with mouse xenograft model revealed that NaBu inhibited aerobic glycolysis in the HCC cells in vivo and in vitro. NaBu induced apoptosis while inhibiting the proliferation of the HCC cells in vivo and in vitro. Furthermore, the compound inhibited the release of lactate and glucose consumption in the HCC cells in vitro and inhibited the production of lactate in vivo. The modulatory effects of NaBu on glycolysis, proliferation and apoptosis were related to its modulation of hexokinase 2 (HK2). NaBu downregulated HK2 expression via c‐myc signalling. The upregulation of glycolysis in the HCC cells induced by sorafenib was impeded by NaBu, thereby enhancing the anti‐HCC effect of sorafenib in vitro and in vivo. Thus, NaBu inhibits the expression of HK2 to downregulate aerobic glycolysis and the proliferation of HCC cells and induces their apoptosis via the c‐myc pathway.

Short chain fatty acids delay the development of hepatocellular carcinoma in HBx transgenic mice

Chronic infection with hepatitis B virus (HBV) is a major risk factor for the development of hepatocellular carcinoma (HCC). The HBV encoded oncoprotein, HBx, alters the expression of host genes and the activity of multiple signal transduction pathways that contribute to the pathogenesis of HCC by multiple mechanisms independent of HBV replication. However, it is not clear which pathways are the most relevant therapeutic targets in hepatocarcinogenesis. Short chain fatty acids (SCFAs) have strong anti-inflammatory and anti-neoplastic properties, suggesting that they may block the progression of chronic liver disease (CLD) to HCC, thereby identifying the mechanisms relevant to HCC development. This hypothesis was tested in HBx transgenic (HBxTg) mice fed SCFAs. Groups of HBxTg mice were fed with SCFAs or vehicle from 6 to 9 months of age and then assessed for dysplasia, and from 9 to 12 months of age and then assessed for HCC. Livers from 12 month old mice were then analyzed for changes in gene expression by mass spectrometry-based proteomics. SCFA-fed mice had significantly fewer dysplastic and HCC nodules compared to controls at 9 and 12 months, respectively. Pathway analysis of SCFA-fed mice showed down-regulation of signaling pathways altered by HBx in human CLD and HCC, including those involved in inflammation, phosphatidylinositol 3-kinase, epidermal growth factor, and Ras. SCFA treatment promoted increased expression of the tumor suppressor, disabled homolog 2 (DAB2). DAB2 depresses Ras pathway activity, which is constitutively activated by HBx. SCFAs also reduced cell viability in HBx-transfected cell lines in a dose-dependent manner while the viability of primary human hepatocytes was unaffected. These unique findings demonstrate that SCFAs delay the pathogenesis of CLD and development of HCC, and provide insight into some of the underlying mechanisms that are relevant to pathogenesis in that they are responsive to treatment.

Chitosan-coated liposomes loaded with butyric acid demonstrate anticancer and anti-inflammatory activity in human hepatoma HepG2 cells

Butyric acid (BA) has been reported to induce anticancer effects on hepatocellular carcinoma (HCC) cells both in vitro and in vivo. However, its delivery and release in cancer tissues must be optimized. On the basis of these requirements, we prepared liposomes coated with chitosan and uncoated liposomes and both types were loaded with BA through a thin-film hydration method. The liposomes coated or uncoated with chitosan had a mean hydrodynamic size of 83.5 and 110.3 nm, respectively, with a homogeneous size distribution of the particles. For evaluation of the biological effects of the nanoformulations, the hepatoblastoma (HB) HepG2 cell line was utilized. BA-loaded liposomes coated with chitosan showed a considerable higher cytotoxicity than both uncoated liposomes and free BA, with IC50 values, after 72 h of incubation, of 7.5, 2.5 and 1.6 mM, respectively. Treatment of HepG2 cells for 5 h with the BA-loaded liposomes coated with chitosan at 5 mM lowered the extent of the increase in IL-8, IL-6, TNF-α and TGF-β expression of approximately 64, 58, 85 and 73.8%, respectively, when compared to the untreated cells. The BA-loaded liposomes coated with chitosan had marked capacity to be internalized in human HB cells showing an increased cytotoxic activity when compared with free BA and important anti-inflammatory effects by inhibiting production of cytokines with a central role in liver cell survival.

Development of a Non-Transformed Human Liver Cell Line with Differentiated-Hepatocyte and Urea-Synthetic Functions: Applicable for Bioartificial Liver

There is a need to develop human hepatocyte cell lines which retain both replicating capacity and highly differentiated functions to facilitate the development of an efficient bioartificial liver. The present study was undertaken to differentiate, using sodium butyrate, the actively replicating immortalized human liver cell line.

The effects of butyrate on cell growth and cell cycle were analyzed, and the albumin synthesis, cytochrome P450 and ammonia-detoxifying activity of the butyrate-treated cells were measured. Butyrate treatment resulted in G2/M arrest of the cell cycle and polygonal changes in the cell morphology. Neither the control nor the butyrate-treated cells showed transformed characteristics. Butyrate treatment increased the amount of albumin secretion, cytochrome P450 activity, and the urea production rate of the cells.

The present study provides non-transformed human hepatocytes, which can replicate unlimitedly and then restore differentiated hepatocyte-specific functions by butyrate, and therefore, have applications for the development of an efficient bioartiflcial liver

Oroxylin A activates PKM1/HNF4 alpha to induce hepatoma differentiation and block cancer progression

Liver cancer is the second cause of death from cancer worldwide, without effective treatment. Traditional chemotherapy for liver cancer has big side effects for patients, whereas targeted drugs, such as sorafenib, commonly have drug resistance. Oroxylin A (OA) is the main bioactive flavonoids of Scutellariae radix, which has strong anti-hepatoma effect but low toxicity to normal tissue. To date, no differentiation-inducing agents have been reported to exert a curative effect on solid tumors. Here our results demonstrated that OA restrained the proliferation and induced differentiation of hepatoma both in vitro and in vivo, via inducing a high PKM1 (pyruvate kinase M1)/PKM2 (pyruvate kinase M2) ratio. In addition, inhibited expression of polypyrimidine tract-binding protein by OA was in charge of the decrease of PKM2 and increase of PKM1. Further studies demonstrated that increased PKM1 translocated into the nucleus and bound with HNF-4α (hepatocyte nuclear factor 4 alpha) directly, promoting the transcription of HNF-4α-targeted genes. This work suggested that OA increased PKM1/PKM2 ratio, resulting in HNF-4α activation and hepatoma differentiation. Especially, OA showed reliable anticancer effect on both human primary hepatocellular carcinoma cells and patient-derived tumor xenograft model for hepatoma, and slowed down the development of primary hepatoma, suggesting that OA could be developed into a novel differentiation inducer agent for hepatoma.

Alterations of epigenetics and microRNA in hepatocellular carcinoma

Studies have shown that alterations of epigenetics and microRNA (miRNA) play critical roles in the initiation and progression of hepatocellular carcinoma (HCC). Epigenetic silencing of tumor suppressor genes in HCC is generally mediated by DNA hypermethylation of CpG island promoters and histone modifications such as histone deacetylation, methylation of histone H3 lysine 9 (H3K9) and tri-methylation of H3K27. Chromatin-modifying drugs such as DNA methylation inhibitors and histone deacetylase inhibitors have shown clinical promise for cancer therapy. miRNA are small non-coding RNA that regulate expression of various target genes. Specific miRNA are aberrantly expressed and play roles as tumor suppressors or oncogenes during hepatocarcinogenesis. We and other groups have demonstrated that important tumor suppressor miRNA are silenced by epigenetic alterations, resulting in activation of target oncogenes in human malignancies including HCC. Restoring the expression of tumor suppressor miRNA by inhibitors of DNA methylation and histone deacetylase may be a promising therapeutic strategy for HCC.

Dual effects of sodium butyrate on hepatocellular carcinoma cells

Sodium butyrate (NaBu), a histone deacetylase inhibitor, has been shown to inhibit cell growth, induce cell differentiation and apoptosis in multiple cell lines. In present study, we revealed the dual effects of NaBu in regulating hepatocellular carcinoma (HCC) cells. In two different HCC cell lines, SK-Hep1 and SMMC-7721, low concentrations of NaBu induced a significant increase in cell growth ratio and S-phase cell percentage, accompanied by a reduced p21 Cip1 expression at both mRNA and protein levels, while dissimilarly, high concentrations of NaBu inhibited cell growth and induced G1 arrest through up-regulation of p21 Cip1 and p27 Kip1 protein expression. The reduction of p45 Skp2 expression further indicated that the ubiquitin-mediated protein degradation might play a role in NaBu-induced up-regulation of p21 Cip1 and p27 Kip1. Moreover, the high concentration of NaBu was also able to trigger HCC cell apoptosis. Taken together, these results demonstrate the distinct effects of NaBu at different dosages. This finding may contribute to develop more effective tumor therapeutic protocols of NaBu in HCC.

Potentials of regenerative medicine for liver disease

Liver transplantation is still the only effective treatment for end-stage liver disease. However, because of the serious worldwide shortage of donated organs, an alternative cellular therapy would be desirable. Animal studies and preclinical trials have indicated that hepatocyte transplantation can serve as an alternative to liver transplantation. Unfortunately, however, the harvesting of hepatocytes is associated with the same problem as organ transplantation, i.e., a lack of a suitable cell source. Therefore, current stem cell technology, which is attempting to establish an unlimited supply of hepatocytes, would facilitate the clinical application of hepatocyte transplantation. This review summarizes current knowledge of embryonic and adult stem cell differentiation into hepatocytes and discusses how liver stem cells could be applied clinically in the future.

Chemoprevention of rat hepatocarcinogenesis with histone deacetylase inhibitors: efficacy of tributyrin, a butyric acid prodrug

Hepatocellular carcinoma (HCC) ranks in prevalence and mortality among top 10 cancers worldwide. Butyric acid (BA), a member of histone deacetylase inhibitors (HDACi) has been proposed as an anticarcinogenic agent. However, its short half-life is a therapeutical limitation. This problem could be circumvented with tributyrin (TB), a proposed BA prodrug. To investigate TB effectiveness for chemoprevention, rats were treated with the compound during initial phases of "resistant hepatocyte" model of hepatocarcinogenesis, and cellular and molecular parameters were evaluated. TB inhibited (p < 0.05) development of hepatic preneoplastic lesions (PNL) including persistent ones considered HCC progression sites. TB increased (p < 0.05) PNL remodeling, a process whereby they tend to disappear. TB did not inhibit cell proliferation in PNL, but induced (p < 0.05) apoptosis in remodeling ones. Compared to controls, rats treated with TB presented increased (p < 0.05) hepatic levels of BA indicating its effectiveness as a prodrug. Molecular mechanisms of TB-induced hepatocarcinogenesis chemoprevention were investigated. TB increased (p < 0.05) hepatic nuclear histone H3K9 hyperacetylation specifically in PNL and p21 protein expression, which could be associated with inhibitory HDAC effects. Moreover, it reduced (p < 0.05) the frequency of persistent PNL with aberrant cytoplasmic p53 accumulation, an alteration associated with increased malignancy. Original data observed in our study support the effectiveness of TB as a prodrug of BA and as an HDACi in hepatocarcinogenesis chemoprevention. Besides histone acetylation and p21 restored expression, molecular mechanisms involved with TB anticarcinogenic actions could also be related to modulation of p53 pathways.

A phase 1/2 trial of arginine butyrate and ganciclovir in patients with Epstein-Barr virus-associated lymphoid malignancies

Malignancies associated with latent Epstein-Barr virus (EBV) are resistant to nucleoside-type antiviral agents because the viral enzyme target of these antiviral drugs, thymidine kinase (TK), is not expressed. Short-chain fatty acids, such as butyrate, induce EBV-TK expression in latently infected B cells. As butyrate has been shown to sensitize EBV(+) lymphoma cells in vitro to apoptosis induced by ganciclovir, arginine butyrate in combination with ganciclovir was administered in 15 patients with refractory EBV(+) lymphoid malignancies to evaluate the drug combination for toxicity, pharmacokinetics, and clinical responses. Ganciclovir was administered twice daily at standard doses, and arginine butyrate was administered by continuous infusion in an intrapatient dose escalation, from 500 mg/(kg/day) escalating to 2000 mg/(kg/day), as tolerated, for a 21-day cycle. The MTD for arginine butyrate in combination with ganciclovir was established as 1000 mg/(kg/day). Ten of 15 patients showed significant antitumor responses, with 4 CRs and 6 PRs within one treatment cycle. Complications from rapid tumor lysis occurred in 3 patients. Reversible somnolence or stupor occurred in 3 patients at arginine butyrate doses of greater than 1000 mg/(kg/day). The combination of arginine butyrate and ganciclovir was reasonably well-tolerated and appears to have significant biologic activity in vivo in EBV(+) lymphoid malignancies which are refractory to other regimens.

Histone deacetylase 1-mediated histone modification regulates osteoblast differentiation

Osteogenesis is a complex process associated with dramatic changes in gene expression. To elucidate whether modifications in chromatin structure are involved in osteoblast differentiation, we examined the expression levels of histone deacetylases (HDACs) and the degree of histone acetylation at the promoter regions of osteogenic genes. During osteogenesis, total HDAC enzymatic activity was decreased with significant reduction in HDAC1 expression. Consistently, recruitment of HDAC1 to the promoters of osteoblast marker genes, including osterix and osteocalcin, was down-regulated, whereas histone H3 and H4 were hyperacetylated at those promoters during osteoblast differentiation. Moreover, suppression of HDAC activity with a HDAC inhibitor, sodium butyrate, accelerated osteogenesis by inducing osteoblast marker genes including osteopontin and alkaline phosphatase. Consistently, knockdown of HDAC1 by the short interference RNA system stimulated osteoblast differentiation. Taken together, these data propose that down-regulation of HDAC1 is an important process for osteogenesis.

Generation of hepatocyte-like cells from human embryonic stem cells

Use of human hepatocytes for therapeutic and drug discovery applications is hampered by limited tissue source and the inability of hepatocytes to proliferate and maintain function long term in vitro. Human embryonic stem (hES) cells are immortal and pluripotent and may provide a cell source for functional human hepatocytes. We report here that hES cells can be induced to differentiate into hepatocyte-like cells. Treatment with sodium butyrate induced hepatic differentiation as well as significant cell death, resulting in approximately 10-15% yield of a homogeneous population of cells. The differentiated cells have morphological features similar to that of primary hepatocytes and 70-80% of the cells express liver-associated proteins (albumin, alpha-1-antitrypsin, cytokeratin 8 and 18), accumulate glycogen, have inducible cytochrome P450 activity, and do not express alpha-fetoprotein. Because of the inherent proliferative capacity of hES cells, these cells may provide a reliable source of normal human hepatocytes for research and transplantation.

Identification of p21WAF1/CIP1 as a direct target of EWS-Fli1 oncogenic fusion protein

Translocation t(11;22) is a karyotypic abnormality detected in over 90% of Ewing's family tumors. This translocation results in the EWS-Fli1 fusion gene, which has been shown to be a potent, single-step transforming gene. We reported previously that suppression of the EWS-Fli1 fusion protein altered the expression of G(1) regulatory cyclins and cyclin-dependent kinase inhibitors both at mRNA and protein levels, resulting in G(1) growth arrest in Ewing's family tumor cell lines. These data suggest that the G(1) regulatory molecules may be targets of the EWS-Fli1 fusion protein, which functions as an aberrant transcription factor. By using electrophoretic mobility shift assays, we show here the direct association of EWS-Fli1 fusion protein with ETS consensus sequences, which are in the promoter of the p21(WAF1/CIP1) gene. Reporter gene assays revealed that the activity of the p21(WAF1/CIP1) promoter is negatively regulated by EWS-Fli1 fusion protein through at least two ETS-binding sites in the promoter. EWS-Fli1 interacted with p300 cotransactivator and suppressed its histone acetyltransferase activity, which may explain the down-regulation of p21(WAF1/CIP1) by EWS-Fli1. In the presence of a histone deacetylase inhibitor, the histone acetyltransferase activity of the Ewing's family tumor cell was recovered resulting in the induction of p21, and the cell growth was dramatically inhibited. These results demonstrated that p21(WAF1/CIP1) might be one of the direct targets of EWS-Fli1, and that p21(WAF1/CIP1) could serve as a target for a molecularly based therapy for Ewing's family tumors.

Histone deacetylase inhibitor trichostatin A induces cell-cycle arrest/apoptosis and hepatocyte differentiation in human hepatoma cells

Remodeling of the chromatin template by inhibition of HDAC activities represents a potential transcriptional therapy for neoplastic disease. A number of HDAC inhibitors that modulate in vitro cell growth and differentiation have been developed. We analyzed the effects of TSA, a specific and potent HDAC inhibitor, on the human hepatoma cell lines HepG2 and Huh-7. TSA increased levels of acetylated histones H3 and H4 in both HepG2 and Huh-7. It inhibited cell proliferation in vitro and induced G(0)/G(1) arrest in HepG2 and apoptosis in Huh-7. Gene expression of liver-specific functions and liver-enriched transcription factors was upregulated by TSA. TSA upregulated the ammonia removal rate and the albumin synthesis rate of HepG2 and Huh-7. Our results indicate that TSA can induce cell-cycle arrest/apoptosis and hepatocyte differentiation in human liver cancer cell lines.

Effect of the molar ratio of branched-chain to aromatic amino acids on growth and albumin mRNA expression of human liver cancer cell lines in a serum-free medium

Supplementation of branched-chain amino acids (BCAAs) is often used for the treatment of hepatic encephalopathy and low albuminemia in Japan. In this scenario, although many cases are complicated with hepatocellular carcinoma in chronic viral infection, the effect of BCAA levels on hepatocellular carcinoma cells remains unclear. We investigated the effect of the molar ratios of BCAAs to aromatic amino acids (AAAs) on the growth and albumin mRNA expression of cultured human liver cancer cell lines, HCC-M, HCC-T, PLC/PRF/5, and Hep G2. To exclude the effect of fetal serum in culture media on modification of the growth and albumin transcription of cell lines, we used a synthetic serum-free medium. We found that an increase in the molar ratio of BCAAs to AAAs reduced the growth of Hep G2 cells, and it increased albumin mRNA expression in this cell line at a molar ratio of 0.1-10. These results suggest that the molar ratio of BCAAs to AAAs affect the growth and mRNA expression of some liver cancer cells, and supplementation of BCAAs may at least be beneficial to patients with cirrhosis, even complicated with liver cancer.

In vitro effects of cholesteryl butyrate solid lipid nanospheres as a butyric acid pro-drug on melanoma cells: evaluation of antiproliferative activity and apoptosis induction

Literature data show that butyric acid derivatives bear a dose-dependent differentiative anti-proliferative activity on cancer cell lines and that apoptosis induction may play a major role. Although it was recently shown that solid lipid nanospheres (SLNs) are a suitable tool for several in vivo drug administration routes, there is little available information on melanoma cell lines. This study was aimed at evaluating the anti-proliferative and apoptotic in vitro effects of cholesteryl butyrate (chol-but) SLNs on melanoma cells. Increasing concentrations of chol-but SLNs were used to test two melanoma cell lines. Both cell lines were treated with Na-butyrate (Na-but) and chol-but SLNs for viability. Those tested with chol-but SLNs were more effective than Na-butirate (3 to 72 h). The apoptotic effects of chol-but SLNs were evaluated between 3 and 72 h by annexin-V (ANX-V)/propidium iodide (PI) staining and the antiproliferative effect by PI staining. Apoptosis anti-proliferative-regulatory proteins as bcl-2, Fas/APO1 (CD95) and PCNA (PC10) were also investigated. Flow cytometric analyses evidenced a G(0/1)-S transition block and a 'sub-G(0/1)' apoptotic peak from 0.5 to 1.0 mM butyric acid. In ANX-V/PI flow cytometric staining, a dose- and time-dependent increase in the apoptotic cell percentage (ANX-V+) coupled with a down-regulation of PC10 and bcl-2 and a parallel up-regulation of Fas/APO1 (CD95) were found in both lines started after 3 to 24 h of chol-but SLNs treatment. Results show that chol-but SLNs exerts a dose/time-dependent effect in melanoma cell apoptosis induction between 3 and 24 h and a dose but not time-dependent effect after 24 h of treatment.

Reduction of c-myc expression by an antisense approach under Cre/loxP switching induces apoptosis in human liver cancer cells

c-Myc has been documented to be both a positive and a negative signal for the induction of apoptosis. It is well known that overexpression of the c-myc gene induces apoptosis of normal cells, but the result of a reduction in its expression is not fully understood. We examined whether a reduction in c-myc expression would induce apoptosis in human liver cancer cells. Specifically, antisense and sense oligodeoxynucleotides (oligos) against the human c-myc mRNA were synthesized, mixed with a liposome reagent at various ratios, and were applied to the liver cancer-derived cell lines, HCC-T, HepG2, and PLC/PRF/5. To exclude effects resulting from using oligos, plasmid vectors expressing the full-length c-myc cDNA in both sense and antisense orientations under the control of the Cre/loxP system were generated. Monoclonal cell lines including these plasmid vectors were produced and Cre was supplied by adenovirus infection. Apoptosis was determined morphologically and c-Myc and Bcl-2 expression was examined by Western blotting. The antisense myc significantly inhibited the proliferation of the cells within two days, while neither the liposome reagent alone nor sense myc did so. Most of the cells were rounded up by the antisense-treatment and nuclear fragmentation and DNA ladder formation were detected after two days in antisense c-myc-treated cells. Antisense c-myc largely reduced c-Myc and partially Bcl-2 expression; overexpression of Bcl-2 partially rescued from apoptosis in HCC-T and HepG2 cells. These results suggest that the massive reduction in c-myc mRNA induces apoptosis in liver cancer cell lines and consequent decrease in Bcl-2 enhances the cell death. c-Myc reduction under the Cre/loxP switching system may be a useful tool for the clarification of c-myc-related cellular mechanisms in differentiation and proliferation.

Reduction of telomerase activity in human liver cancer cells by a histone deacetylase inhibitor

The presence of telomerase has been demonstrated recently in many different malignancies. Several reports documented that in human hepatocellular carcinoma, the level of telomerase activity parallels its differentiation stage. In the present study, the effect of the differentiation-inducing agent sodium butyrate on telomerase activity in four human liver cancer cell lines was investigated using the telomeric repeat amplification protocol. We assayed telomerase activity before and after butyrate treatment and in cell cycle synchronized non-dividing quiescent cells. In addition, telomerase reverse transcriptase levels were measured at the mRNA level. All four cell lines possessed high but not identical levels of telomerase activity. Telomerase activity was significantly reduced by treatment with sodium butyrate as well as trichostatin A in a dose- and time-dependent fashion, paralleling the reduction of cell proliferation. Although methotrexate, hydroxyurea, and colchicine synchronized the cell cycle at G1, S, and G2/M, respectively, and thereby also caused proliferating cells to cease dividing and become quiescent, in this case telomerase activity remained essentially unaltered compared to the control cultures. Moreover, levels of mRNA encoding telomerase reverse transcriptase were not always significantly altered by either sodium butyrate treatment or cell cycle synchronization. These results suggest that sodium butyrate, as a histone deacetylase inhibitor, effectively reduces telomerase activity without affecting transcription levels of the reverse transcriptase component.

Up-regulation of E-cadherin and I-catenin in human hepatocellular carcinoma cell lines by sodium butyrate and interferon-alpha

Human E-cadherin is a homophilic cell adhesion molecule and its expression is well preserved in normal human hepatocytes; a decrease in its expression has been observed in poorly differentiated hepatocellular carcinoma cells. We examined the alteration of E-cadherin and catenin expressions caused by differentiation inducers in human hepatocellular carcinoma cells. Hepatocellular carcinoma cell lines, HCC-T and HCC-M, were cultured with all-trans retinoic acid (ATRA), dexamethasone (DEX), sodium butyrate, and interferon-alpha. E-cadherin expression was only up-regulated by butyrate and interferon-alpha (IFN-alpha) in both cell lines, studied by means of fluorescence immunostaining and flow cytometry. The localization of E-cadherin staining was shown at their cell membrane. According to the increase in E-cadherin expression, beta-catenin expression appeared at the cell membrane of both cell lines when treated with butyrate and IFN-alpha. Such an appearance was not observed when cells were treated with ATRA and DEX. Western blotting showed that alpha- and y-catenin expression was not changed, while only the expression of beta-catenin increased. Beta-catenin oncogenic activation as a result of amino acid substitutions or interstitial deletions within or including parts of exon 3, which has been demonstrated recently, was not detected in these cell lines by direct deoxyribonucleic acid sequencing. These results suggest that the expression and interaction between E-cadherin and wild-type beta-catenin are potentially modulated by butyrate and IFN-alpha, and that these two agents are potent inhibitors of hepatocellular carcinoma cell invasion and metastasis.

Two-dimensional electrophoresis map of the human hepatocellular carcinoma cell line, HCC-M, and identification of the separated proteins by mass spectrometry

Currently, one of the most popular applications of proteomics is in the area of cancer research. In Africa, Southeast Asia, and China, hepatocellular carcinoma is one of the most common cancers, occurring as one of the top five cancers in frequency. This project was initiated with the purpose of separating and identifying the proteins of a human hepatocellular carcinoma cell line, HCC-M. After two-dimensional gel electrophoresis separation, silver staining, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analyses, tryptic peptide masses were searched for matches in the SWISS-PROT and NCBI nonredundant databases. Approximately 400 spots were analyzed using this approach. Among the proteins identified were housekeeping proteins such as alcohol dehydrogenase, alpha-enolase, asparagine synthetase, isocitrate dehydrogenase, and glucose-6-phosphate 1-dehydrogenase. In addition, we also identified proteins with expression patterns that have been postulated to be related to the process of carcinogenesis. These include 14-3-3 protein, annexin, prohibitin, and thioredoxin peroxidase. This study of the HCC-M proteome, coupled with similar proteome analyses of normal liver tissues, tumors, and other hepatocellular carcinoma cell lines, represents the first step towards the establishment of protein databases, which are valuable resources in studies on the differential protein expressions of human hepatocellular carcinoma.

Secretion of phospholipid transfer protein by human hepatoma cell line, Hep G2, is enhanced by sodium butyrate

Hep G2 cells were used to study the synthesis and secretion of phospholipid transfer protein (PLTP). Upon incubation of the cells at confluence with serum-free Dulbecco's modified Eagle's medium (DMEM), phosphatidylcholine (PC) transfer activity was found to accumulate in the culture media. The PC transfer activity in the media was effectively inhibited by rabbit anti-human PLTP immunoglobulin (Ig)G, thus indicating that the PC transfer activity was due to secreted PLTP. The molecular weight of Hep G2 PLTP was approximately 78 kDa by Western blot analysis, in agreement with the molecular weight obtained for purified human plasma PLTP. The PLTP secreted by Hep G2 also possessed an HDL conversion activity similar to that of human plasma PLTP. The addition of butyrate to the cell culture media resulted in a marked increase in the secretion of PLTP. After 24 h incubation with 4 mmol/L sodium butyrate, a more than twofold increase (P < 0.01) of PC transfer activity in the cell-conditioned media was obtained. The dose-dependent increase in the PC transfer activity in the media upon butyrate treatment was well correlated (r = 0.80, P < 0.01) with that of PLTP mass as determined by immuno-slot blot analysis of cell-conditioned media. The increased secretion of PLTP by Hep G2 treated with sodium butyrate was accompanied by a greater increase in the level of PLTP mRNA in the cells as determined by ribonuclease protection assay. In the presence of 4 mmol/L sodium butyrate, a fourfold increase (P < 0. 01) in mRNA level was obtained at 24 h. No stabilizing effect of butyrate on PLTP mRNA was apparent upon treatment of the cultured cells with the RNA synthesis inhibitor, actinomycin D. Thus, the up-regulatory effect of butyrate on PLTP gene expression seemed to have occurred at the transcriptional level.

Sodium butyrate induces alkaline phosphatase gene expression in human hepatoma cells

BACKGROUND AND AIMS

Butyrate, a natural product of colonic bacterial flora, has been reported to increase the activities of a number of enzymes, including alkaline phosphatase, (ALP) in several cancer cell lines. However, butyrate-induced ALP gene expression in human hepatoma cells has not been previously demonstrated. In the present study, the effects of sodium butyrate on cell growth and proliferation, cellular activity and expression of ALP gene in human hepatoblastoma-derived HepG2 cells were investigated.

METHODS

The HepG2 cells were treated with sodium butyrate (0-1 mmol/L) and the number of viable cells were counted at 24, 48 and 72 h after treatment. A [3H]-thymidine incorporation study was performed at different concentrations of sodium butyrate for 48 h. The cellular activity of ALP in HepG2 cells by sodium butyrate was measured by a substrate-specific enzymatic assay. To elucidate the effects of sodium butyrate on ALP gene expression, a northern blotting experiment employing hybridization with mouse placental ALP cDNA was performed.

RESULTS

Cell growth and proliferation were dose-dependently inhibited by sodium butyrate. Cellular ALP activity was significantly increased in HepG2 cells in a time- and dose-dependent fashion by treatment with sodium butyrate and a maximum activity was observed at 48 h. These effects were reversible when sodium butyrate was removed from the culture medium. By northern blot analysis, the level of ALP messenger RNA was dose-dependently elevated by sodium butyrate.

CONCLUSION

Butyrate, at a concentration relevant to the normal physiology of the liver, causes augmented expression of ALP mRNA in HepG2 cells. We assume that increased ALP synthesis in HepG2 cells by sodium butyrate results from an enhanced rate of transcription rather than translation of mRNA.

Identification and chromosomal localization of CTNNAL1, a novel protein homologous to alpha-catenin

Sodium butyrate (NaB) was shown to induce growth inhibition and apoptosis in a human pancreatic cancer cell line (AsPC-1). To identify the genes that are differentially regulated by NaB, we generated subtracted EST libraries highly enriched for up- or down-regulated transcripts using the suppression subtraction hybridization technique. One of the ESTs identified in the down-regulated library showed significant homology to human alpha-catenin. A cDNA of 2.45 kb that codes for a putative protein of 734 aa was cloned. The cloned cDNA was used as a template in an in vitro transcription-translation reaction. This produced a protein product of about 82 kDa in size. The gene designated as CTNNAL1 (catenin (cadherin-associated protein), alpha-like 1) was found to be ubiquitously expressed in many tissues including pancreas, heart, and skeletal muscle. A human BAC clone containing the gene was isolated and used as a probe for fluorescence in situ hybridization (FISH). Both radiation hybrid and FISH analysis mapped the gene to chromosome band 9q31.2, a region where frequent abnormalities have been observed in bladder carcinoma, esophageal cancers, and several other tumors.

Phenotypic characterization of rat hepatoma cell lines and lineage-specific regulation of gene expression by differentiation agents

Hepatoma cell lines can be characterized by their expression of hepatocyte- and biliary-specific genes and by their response to differentiating agents in a lineage-dependent manner. These characteristics can be used to map the maturational lineage position of the cell lines. Tissue-specific gene expression and regulation by heparin, dimethylsulfoxide (DMSO), and sodium butyrate (SB) were examined in three rat hepatoma cell lines and two rat liver epithelial cell lines. Based on antigenic profiles and gene expression in serum-supplemented medium, the hepatoma cell lines could be organized in distinct categories of hepatic differentiation. All three hepatomas expressed the following five genes: gamma-glutamyl transpeptidase (GGT), glutathione-S-transferase pi (Yp), glutamine synthetase, and alpha 5 and beta 1 integrin. Cell line H4AzC2 also expressed alpha-fetoprotein (AFP), albumin. IGF II receptor, and the biliary/oval cell antigens OC.2 and OC.3, a phenotype characteristic of fetal hepatocytes. FTO-2B cells lacked AFP, OC.2, and OC.3 but expressed albumin and IGF II receptor in addition to the five commonly expressed genes, consistent with a more hepatocyte-like phenotype. Cell line H5D-7 expressed neither albumin nor the IGF II receptor, but did express OC.2, OC.3, and alpha 3 integrin in addition to the five commonly expressed genes, characteristic of biliary epithelial cells. Regulation of gene expression by heparin, DMSO, and SB was examined in cells cultured in hormonally defined medium. The patterns of regulation of AFP, albumin, GGT, and Yp were dependent upon the state of differentiation of the cell. FTO-2B cells regulated genes in a manner similar to that of E16 fetal hepatocytes, H4AzC2 regulated genes characteristic of both hepatocytic and biliary lineages, and H5D.7 regulated only biliary genes. Suppression of GGT by DMSO was uniformly observed. The three cell lines expressed equal amounts of HNF-4, but FTO-2B cells expressed more HNF-3 beta and less HNF-3 alpha, while the reverse was true of H4AzC2 and H5D.7 cells.

Loss of butyrate-induced apoptosis in human hepatoma cell lines HCC-M and HCC-T having substantial Bcl-2 expression

We have demonstrated that sodium butyrate induces differentiation in human hepatoma cells; however, recent studies have shown that this agent causes apoptosis in some types of cancer cells. In this study, we examined whether sodium butyrate causes apoptosis in the human hepatoma cell lines, HCC-M and HCC-T. The growth of human hepatoma cells was dose-dependently reduced by sodium butyrate. Flow cytometric analysis showed cell-cycle arrest at the G1 phase in the sodium butyrate-treated cells. Apoptotic change was never found in treated cells at concentration levels of less than 5 mmol/L. Sodium butyrate decreased p53 expression and increased p21WAF-1 expression in HCC-T and HCC-M cells having the wild-type p53 gene. Western blot analysis showed that Bcl-2 was expressed in the HCC-T and HCC-M cells, and its expression was increased after exposure to sodium butyrate. Antisense oligodeoxynucleotide against bcl-2 easily caused apoptosis. These results indicate that sodium butyrate hardly induces apoptotic change in the human hepatoma cell lines, HCC-T and HCC-M, with the increase of Bcl-2 expression. Cell-cycle arrest in the G1 phase caused by sodium butyrate was suggested to be induced by the increase in p21WAF-1 expression, but this change did not link with the p53 increase.

Downregulation of a human colonic sialyltransferase by a secondary bile acid and a phorbol ester

Fecal constituents such as bile acids and increased sialylation of membrane glycoproteins by alpha-2,6-sialyltransferase (HST6N-1) may contribute to colorectal tumorigenesis. We hypothesized that bile acids and phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] would upregulate HST6N-1 in colonic cells. However, deoxycholate (DOC) (300 mumol/l), a secondary bile acid, and TPA (20 ng/ml) decreased expression of an approximately 100-kDa glycoprotein bearing alpha-2,6-linked sialic acid in a colon cancer cell line (T84) in vitro. HST6N-1 mRNA levels were reduced approximately 80% by treatment (< or = 24 h) with DOC or TPA but not by cholate, a primary bile acid. Treatment (24 h) with DOC or TPA decreased activity of this enzyme to 30% and 13% of control, respectively. These effects of DOC and TPA were transcriptional and were mediated by Ca2+ and protein kinase C, respectively. Thus DOC and TPA both downregulated, and did not upregulate, alpha-2,6-sialyltransferase expression in vitro, but by different transduction pathways. As colorectal tumors grow, their progressive removal from the fecal milieu that normally downregulates this enzyme may favor invasion and metastasis.

Inhibition of platelet-derived growth factor BB-induced expression of glyceraldehyde-3-phosphate dehydrogenase by sodium butyrate in rat vascular smooth muscle cells

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key regulatory enzyme of glycolysis, which exists in nuclei and functions as a DNA-binding protein as well as a nuclear protein, appears to be modulated by cellular activities. Exposure of quiescent rat smooth muscle cells (SMCs) to platelet-derived growth factor BB (PDGF-BB), which stimulates SMCs proliferation, caused a time-dependent increase in mRNA for GAPDH and its catalytic activity. Treatment of quiescent SMCs with sodium butyrate (SB), which is shown to inhibit PDGF-BB-induced SMC proliferation, caused a time- and concentration-dependent decrease in PDGF-BB-induced GAPDH mRNA expression and its catalytic activity. Nuclear run-on studies revealed that the PDGF-BB-induced rate of GAPDH gene transcription was reduced by about 50% in the presence of 5 mmol/L SB. The protein synthesis inhibitor, cycloheximide, failed to abolish the SB-inhibited PDGF-BB-induced rate of transcription of GAPDH, suggesting that SB is not dependent on ongoing protein synthesis to exert its effects on PDGF-BB-induced GAPDH transcription. Furthermore, measurement of GAPDH mRNA stability at various times after the inhibition of transcription with actinomycin D indicated that 5 mmol/L SB has no significant effect on the half-life of PDGF-BB-induced mRNA. The reduction in PDGF-BB-induced GAPDH expression by SB is probably caused by a cycloheximide-insensitive transcriptional mechanism. Thus, the inhibition of PDGF-BB-induced expression of GAPDH by SB suggests a link between SMC proliferation, energy consumption, and GAPDH gene upregulation.

Butyrate activates the WAF1/Cip1 gene promoter through Sp1 sites in a p53-negative human colon cancer cell line

Butyrate is a well known colonic luminal short chain fatty acid, which arrests cell growth and induces differentiation in various cell types. We examined the effect of butyrate on the expression of WAF1/Cip1, a potent inhibitor of cyclin-dependent kinases, and its relation to growth arrest in a p53-mutated human colon cancer cell line WiDr. Five millimolar butyrate completely inhibited the growth of WiDr and caused G1-phase arrest. WAF1/Cip1 mRNA was rapidly induced within 3 h by treatment with 5.0 mM butyrate, and drastic WAF1/Cip1 protein induction was detected. Using several mutant WAF1/Cip1 promoter fragments, we found that the butyrate-responsive elements are two Sp1 sites at -82 and -69 relative to the transcription start site. We also found that a TATA element at -46 and two overlapping consensus Sp1 sites at -60 and -55 are essential for the basal promoter activity of WAF1/Cip1. These findings suggest that butyrate arrests the growth of WiDr by activating the WAF1/Cip1 promoter through specific Sp1 sites in a p53-independent fashion.

Modulation effects of hexamethylene bisacetamide on growth and differentiation of cultured human malignant glioma cells

The modulation effects of hexamethylene bisacetamide (HMBA), a differentiation-inducing agent, on growth and differentiation of cells from human malignant glioma cell line SHG-44 were studied. At cytostatic doses (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 15 days), HMBA exerted a marked inhibitory effect on cell proliferation. Exposure to HMBA (5 mM and 10 mM for 12 days) also resulted in an accumulation of cells in G0/G1 phase and a decrease of cells in S phase as analyzed by flow cytometry. The reversible effects of 7.5 mM HMBA and 10 mM HMBA on cell proliferation and 10 mM HMBA on disruption of cell cycle distribution were observed when HMBA was removed from culture media on Day 6 and replaced with HMBA-free media. Colony-forming efficiency (CFE) in soft agar was remarkably decreased by HMBA (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 14 days), and in 7.5 mM HMBA- and 10 nM HMBA treated cells, the CFEs were reduced to 25% and 12.5%, respectively, of that in untreated cells. Cells treated with HMBA (5 mM and 10 mM for 15 days) remained tumorigenic in athymic nude mice, but the growth rates of the xenografts were much slower than those in the control group. The effects of HMBA on cell proliferation, cell cycle distribution, CFE, and growth of xenografts were dose dependent. A more mature phenotype was confirmed by the morphological changes from spindle shape to large polygonal stellate shape and remarkably elevated expression of glial fibrillary acidic protein in cells exposed to HMBA (5 mM, 10 mM for 15 days). Our results showed that a more differentiated phenotype with marked growth arrest was induced in SHG-44 cells by HMBA.

Sodium butyrate inhibits platelet-derived growth factor-induced proliferation of vascular smooth muscle cells

Sodium butyrate (SB), a naturally occurring short-chain fatty acid, was investigated for its therapeutic value as an antiproliferative agent for vascular smooth muscle cells (SMCs). At 5-mmol/L concentration, SB had no significant effect on rat SMC proliferation. However, at the same concentration, SB inhibited platelet-derived growth factor (PDGF)-AA-, -AB-, and -BB-induced proliferation of SMCs. Exposure of SMCs to PDGF-BB resulted in activation of receptor intrinsic tyrosine kinase activity and autophosphorylation of beta-PDGF-receptor (beta-PDGFR). The activated beta-PDGFR physically associated and phosphorylated signaling molecules such as ras-GTPase activating protein (GAP) and phospholipase C gamma (PLC gamma). SB, in the absence of PDGF-BB, caused neither beta-PDGFR tyrosine phosphorylation nor phosphorylation and association of GAP and PLC gamma with beta-PDGFR. PDGF-BB-enhanced activation of receptor intrinsic tyrosine kinase activity and autophosphorylation of tyrosine residues of beta-PDGFR were unaffected by SB irrespective of whether SMCs were preincubated with SB before exposure to PDGF-BB plus SB or incubated concomitantly with PDGF-BB plus SB. Likewise, phosphorylation and association of GAP and PLC gamma with PDGF-BB-activated beta-PDGFR were unaffected. In addition, SB did not block PDGF-BB-stimulated, PLC gamma-mediated production of inositol triphosphate. Similarly, PDGF-BB-induced beta-PDGFR degradation was unaffected when SMCs were exposed to PDGF-BB plus SB, and SB by itself had no influence on beta-PDGFR degradation. Unlike beta-PDGFR kinase activity, mitogen-activated protein kinase (MAP-kinase) activity was stimulated by SB by about 2.7-fold. Exposure of SMCs to PDGF-BB caused an approximately 11.4-fold increase in MAP-kinase activity and this increase in activity was not significantly affected when cells were coincubated with PDGF-BB and SB (10.3-fold). However, pretreatment of SMCs with SB for 30 minutes and subsequent incubation in PDGF-BB plus SB abolished most of the PDGF-BB-induced MAP-kinase activity (4.6-fold). Transcription of growth response genes such as c-fos, c-jun, and c-myc were induced by PDGF-BB, and their induction was suppressed, particularly c-myc, by incubating SMCs with PDGF-BB plus SB. Similarly, preincubation of cells with SB for 30 minutes and subsequent incubation in PDGF-BB plus SB diminished PDGF-BB-induced transcription of c-fos, c-jun, and c-myc. However, SB by itself had no significant effect on c-fos, c-jun, and c-myc transcription.(ABSTRACT TRUNCATED AT 400 WORDS)

Maturation-dependent changes in the regulation of liver-specific gene expression in embryonal versus adult primary liver cultures

During rat liver development, which starts on day 10 of embryogenesis (E10), and until E15, all parenchymal cells are thought to be a homogeneous population of bipotential progenitors, able to give rise to both hepatocytes and bile duct epithelial cells. We established primary liver cultures from embryonic livers at various developmental stages, from E14 to neonates, as well as adult rats. Gene expression and regulation by three known differentiating agents, heparin, dimethylsulfoxide (DMSO), and sodium butyrate, were examined in these primary cultures. Alpha-fetoprotein (alpha-FP), albumin, gamma-glutamyltranspeptidase (GGT), and glutathione-S-transferase-P (Yp) were expressed by cultured liver cells through fetal development, whereas insulin-like growth factor-II (IGF II) receptor, expressed in fetal parenchymal cells, was not present in cultured neonatal cells. Heparin increased alpha-FP levels in fetal liver cells, but not in cells obtained after birth. The expression of GGT and Yp was coordinately regulated. The two genes were up-regulated by sodium butyrate and down-regulated by DMSO in cultured liver cells from all embryonal ages tested. However, the regulation of these two genes by sodium butyrate and DMSO was not apparent in neonatal and adult liver cultures. Sodium butyrate increased alpha-FP and albumin mRNA expression in E14 and E15 cells, but not in E16, neonatal or adult cultures, and its addition caused heterogenous expression of albumin. We conclude that the regulation of gene expression in primary liver cultures by the three agents tested is altered after birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody-dependent cell-mediated cytotoxicity against cell lines generated by liver-specific idiotype-bearing antibody

We produced a murine monoclonal antibody (mAb), designated H2-mAb, against a fractionated soluble phase of human liver homogenate which antibody reacted with human liver cells. A human antibody possessing the same idiotype as the H2-mAb, designated LSIA (liver-specific idiotype-bearing antibody), can be measured by a sandwich enzyme-linked immunosorbent assay, using the anti-H2 idiotype antibody. The serum level of LSIA in patients with histologically proven chronic hepatitis (CH) was significantly higher than that in healthy subjects and it was also higher than that in subjects with other diseases, including systemic lupus erythematosus. In a comparison between patients with CH type B and those with CH type C, there was no significant difference in serum levels of LSIA. It was possible to purify LSIA from the sera of patients with CH. The purified LSIA bound to the human cell lines Chang and HCC-M, derived from liver cells and a hepatoma respectively, but not to HeLa cells, a uterine carcinoma derivative. The reactivity of this mAb to HCC-M was weaker than that to Change. Moreover, the presence of LSIA caused an antibody-dependent cell-mediated cytotoxic challenge against Change cells in vitro.

Analysis of c-fos expression in the butyrate-induced F-98 glioma cell differentiation

The functional induction of c-fos in the sodium butyrate-induced differentiation of F-98 glioma cells was studied. Fos protein level was increased by butyrate. In contrast, c-Jun protein was constitutively expressed and was not affected by butyrate. Gel-retardation assay indicates Fos as a component of the complex formed between the consensus oligonucleotide of the TPA (PMA, phorbol 12-myristate 13-acetate) response element (TRE) and nuclear extract prepared from butyrate-treated cells. Transfection studies showed that butyrate increased transcription from a multimeric TRE-driven reporter construct, and the effect was mimicked by transfecting cells with fos-expression plasmid. Furthermore, under conditions of c-fos over-expression, transactivation by butyrate was essentially abolished. These data suggest that Fos induction had a functional role in gene activation. Characterization of stable c-fos transfectants demonstrated that these cells displayed alterations in morphology, showed serum-dependent growth, had slower growth rates and grew to lower saturation densities than did untransfected F-98 cells or transfected cells that did not express c-fos. Immunofluorescent staining indicated that fos transfectants also had elevated glial fibrillary acidic protein ('GFAP') expression. Transfection of the c-fos promoter-chloramphenicol acetyltransferase fusion gene into F-98 cells revealed that activation of c-fos by butyrate was exerted at the promoter level, and sequences located within nucleotides -757 to -402 of the c-fos promoter were responsible for butyrate induction. Our data indicate that transcriptional activation of c-fos through its promoter by butyrate resulted in increased Fos protein expression. Transfection studies show that both c-fos and butyrate activate TRE-containing genes, and fos may be a downstream mediator of butyrate. Furthermore, expression of c-fos plays a major role in modulating the growth properties of F-98 cells.

Changes of antigen expression on human hepatoma cell lines caused by sodium butyrate, a differentiation inducer

We have previously reported the effect of a differentiation inducer, sodium butyrate (SB), on human hepatocellular carcinoma (HCC) cell lines, demonstrating that it was a potent inducer of differentiation. In the present study, we investigated the alteration in expression of an antigen defined by a murine monoclonal antibody, H2, as well as alterations in the expression of other antigens, on the HCC cell lines HCC-T, HCC-M, and PLC/PRF/5, since it is known that specific antigenic changes occur during the differentiation of leukemic cells. The expression of the antigen defined by H2 increased immunocytochemically on HCC-T, HCC-M, and PLC/PRF/5 during treatment with SB. A flowcytometric study showed that almost all the HCC-T and HCC-M cells treated with SB highly expressed this antigen after 5 days' treatment. The antigen expression detected by H2 decreased after the removal of SB from the medium. On the other hand, antigen expression detected by another monoclonal antibody, 5C11, was not changed by this treatment. The expression of intracellular adhesion molecule (ICAM)-1 in HCC-T increased slightly, but that of beta 2-microglobulin and HLA-DR did not change. These results demonstrated that some antigen expression was changed by SB treatment and that the antigen defined by H2 seemed to be highly expressed on human HCC cells in the differentiated state.

Reciprocal regulation of alpha-fetoprotein and albumin gene expression by butyrate in human hepatoma cells

BACKGROUND/AIMS

Butyrate, a product of colonic bacterial flora, functions as an antiproliferative agent and induces cell differentiation in a variety of cell types. In the present study, the effects of butyrate on cell growth and expression of alpha-fetoprotein (AFP) and albumin genes in HuH-7 human hepatoma cells were investigated.

METHODS

The HuH-7 cells were treated with sodium butyrate (0-1 mmol/L), and numbers of viable cells were counted at 24, 48, and 72 hours after treatment. To elucidate the effects of sodium butyrate on AFP and albumin gene expression, Northern blotting and transient chloramphenicol acetyltransferase plasmid transfection experiments were performed.

RESULTS

Cell growth was dose dependently inhibited by sodium butyrate. By Northern blot analysis, the level of AFP messenger RNA was reduced by treatment with sodium butyrate, whereas the level of albumin messenger RNA was elevated by this treatment. In transient chloramphenicol acetyltransferase plasmid transfection experiments, sodium butyrate repressed the AFP promoter activity but did not change the AFP enhancer or silencer activities. In contrast, the albumin promoter activity was stimulated by sodium butyrate.

CONCLUSIONS

These results suggest that butyrate leads to the reciprocal differentiating regulation of AFP and albumin gene expression at the transcriptional level in human hepatoma cells.

The expression of human plasma cholesteryl-ester-transfer protein in HepG2 cells is induced by sodium butyrate. Quantification of low mRNA levels by polymerase chain reaction

Although human plasma cholesteryl-ester-transfer protein (CETP) is primarily synthesized in the liver, its expression in a number of transformed liver cell lines is very low. However the use of the human hepatoma cell line HepG2 as a model system for the regulation of CETP on mRNA level is facilitated by a quantitative reverse-transcribed polymerase chain reaction. We demonstrate a time-dependent and concentration-dependent 3-4-fold induction of CETP mRNA by sodium butyrate. CETP mass in the medium is also augmented; however, the effect on protein level is less pronounced.