Human Hepatoma SMMC-7721 Cells Research Articles

Effects of oxymatrine on proliferation and apoptosis in human hepatoma cells

Oxymatrine, a natural quinolizidine alkaloid, has been known having cytotoxic and chemopreventive effects on various cancer cells. To investigate the possible mechanism of oxymatrine's role on cancer cells, in the present study, we examined further the effects of oxymatrine on the growth, proliferation, apoptosis and expression of bcl-2 and p53 gene in human hepatoma SMMC-7721 cells in vitro. Our results show that oxymatrine notably inhibits the growth and proliferation of SMMC-7721 cells and it present a dose-dependence and time-dependence manner within definite reacting dose and time. Oxymatrine block SMMC-7721 cells in G 2/M and S phase; prevent cells entering into G 0/G 1 phase. It results in an obvious accumulation of G 2/M and S phase cells while decrease of G 0/G 1 phase cells. Oxymatrine induce apoptosis of SMMC-7721 cells and apoptotic rate amount to about 60% after treatment with 1.0 mg/ml oxymatrine for 48 h. We also find that oxymatrine down-regulate expression of bcl-2 gene while up-regulate expression of p53 gene. These results demonstrate that oxymatrine inhibit the proliferation and induce apoptosis of human hepatoma SMMC-7721 cells, and suggest that this effect was mediated probably by a significant cell cycle blockage in G 2/M and S phase, down-regulation of bcl-2 and up-regulation of p53.

The hyper-radiosensitivity effect of human hepatoma SMMC-7721 cells exposed to low dose γ-rays and 12C ions

Hypersensitive response of mammalian cells in cell killing to X- and γ-rays has been reported at doses below 1Gy. The purpose of this study was to examine the low dose sensitivity of human hepatoma SMMC-7721 cells irradiated with 60Co γ-rays and 50MeV/u 12C ions. Experiments using γ-rays and charged particle irradiation were performed, particularly in the low dose range from 0 to 2Gy. The survival effect of SMMC-7721 cells was measured by means of standard clonogenic assay in conjunction with a cell sorter. The result indicates SMMC-7721 cells showed hyper-radiosensitive response at low doses and increased radio-resistance at larger single doses for the carbon ions (LET=45.2keV/μm) and the γ-rays. However, the HRS/IRR effect caused by high-LET irradiation is different from that by low-LET radiation. This might possibly be due to the difference in the mode of energy deposition by particle beam and low-LET irradiation.

Inhibition of human telomerase reverse transcriptase gene expression by gambogic acid in human hepatoma SMMC-7721 cells

The activation of human telomerase, a process regulated by the human telomerase reverse transcriptase (hTERT), is a crucial step during cellular immortalization and malignant transformation. We have reported that gambogic acid (GA), a natural product isolated from the gamboge resin of Garcinia hanburyi tree, is an effective telomerase inhibitor and thus displays potent anticancer activity both in vitro and in vivo. Here we present the direct interaction of GA with oncogene c-MYC, a ubiquitous transcription factor involved in the control of cell proliferation and differentiation, as the molecular mechanism of GA's inhibitory effect on telomerase activity. Consistent with the recently reported association between c-MYC overexpression and induction of telomerase activity, we find here that GA treatment of a human hepatoma cell line SMMC-7721 significantly reduced the expression of c-MYC in a time- and concentration-dependent manner accompanied with the down-regulation of the hTERT transcription and the ultimate reduction in telomerase activity. Our results indicate that the hTERT is a target of c-MYC activity and identify a feasible mechanism of GA's potent anticancer activity.

Inhibitory effects of thioredoxin reductase antisense RNA on the growth of human hepatocellular carcinoma cells

Thioredoxin reductase (TrxR) in conjunction with thioredoxin (Trx) is a ubiquitous intracellular oxidoreductase system with antioxidant and redox regulatory roles. In some human tumors, the thioredoxin system is found overexpressed. We have used an antisense approach to investigate whether inhibition of TrxR overexpression can suppress the growth of human hepatocellular carcinoma SMMC-7721 cells. TrxR cDNA fragment was inserted in the antisense direction into pcDNA3.1/myc-His and SMMC-7721 cells were stably transfected with the plasmid construct. The results showed that TrxR antisense RNA could significantly reduce TrxR mRNA level and activity, and suppress the growth of SMMC-7721 cells. Cell-cycle analysis showed G2/M phase arrest in SMMC-7721 cells transfected with TrxR antisense plasmid. TrxR antisense RNA could significantly increase p53 mRNA level and decrease Bcl-2 mRNA level by reverse transcriptase-polymerase chain reaction (RT-PCR). Furthermore a significant decrease in human telomerase reverse transcriptase (hTERT) mRNA level was found in SMMC-7721 cells transfected with TrxR antisense plasmid. Flow cytometry and telomere fluorescence in situ hybridization (Flow FISH) showed that TrxR antisense RNA could significantly reduce the telomere fluorescence in SMMC-7721 cells. The results suggested that TrxR antisene RNA inhibited the growth of SMMC-7721 cells through an accumulation of cell cycle at G2/M phase, an increase in p53 mRNA level and a reduction in telomere fluorescence and Bcl-2, hTERT mRNA levels.

Therapeutic Effect of Fe<SUB>2</SUB>O<SUB>3</SUB> Nanoparticles Combined with Magnetic Fluid Hyperthermia on Cultured Liver Cancer Cells and Xenograft Liver Cancers

The therapeutic effect of Fe2O3 nanoparticles combined with magnetic fluid hyperthermia (MFH) on human hepatocarcinoma SMMC-7721 cells in vitro and xenograft liver cancer in nude mice is studied. We examined growth and apoptosis of SMMC-7721 cells treated with MFH containing Fe2O3 nanoparticles at various concentrations (2, 4, 6, and 8 g/liter) for 30-60 min by using MTT, flow cytometry (FCM), and transmission electron microscopy (TEM). We also observed weight and volume inhibitory rates of the tumors of SMMC-7721-bearing nude mice by using animal experiments. The results showed that Fe2O3 nanoparticles combined with MFH could significantly inhibit the proliferation and increase the ratio of apoptosis of SMMC-7721 cells, and the effect was dose-dependent. The inhibitory rate was 26.5%, 33.53%, 54.4%, and 81.2%, respectively, and the apoptosis rate was 30.26%, 38.65%, 50.28%, and 69.33%, respectively. Animal experiments showed that tumors became small. The weight inhibitory ratio was 42.10%, 66.34%, 78.5%, and 91.46%, and the volume inhibitory ratio was 58.77%, 80.44%, 93.40%, and 98.30%, respectively. Compared with the control and experimental groups, each group had statistically significant difference (p < 0.05). So, Fe2O3 nanoparticles combined with MFH could inhibit the proliferation and induce apoptosis of SMMC-7721 cells and also has a significant inhibitory effect on the weight and volume of xenograft liver cancer. However, the mechanism remains to be further investigated.

Docetaxel shows radiosensitization in human hepatocellular carcinoma cells

To determine the radiosensitizing potential of docetaxel in human hepatocellular carcinoma SMMC-7721 cells and its mechanisms. SMMC-7721 cells were incubated with docetaxel at 0.125, 0.25, and 0.5 nmoL/L for 24 h and at 0.125 and 0.25 nmol/L for 48 h before irradiation. Radiation doses were given from 0 to 10 Gy. Cell survival was measured by a standard clonogenic assay after a 9-d incubation. The reactive oxygen species (ROS) and glutathione (GSH) are detected after being given the same dose of docetaxel for the same time. The sensitization enhancement ratios (SER) for SMMC-7721 cells determined at the 50% survival level were 1.15, 1.21 and 1.49 at 0.125, 0.25, and 0.5 nmol/L for pre-incubation of 24 h, respectively; the SER were 1.42, 1.67 at 0.125 and 0.25 nmol/L, for pre-incubation of 48 h, respectively. The ROS of SMMC-7721 cells increased and GSH decreased after pretreatment with the same doses of docetaxel for 24 or 48 h. A radiosensitizing effect of docetaxel could be demonstrated unambiguously in this cell line used. In addition, our data showed that the mechanism of radiopotentiation by docetaxel probably does not involve a G2/M block in SMMC-7721 cells, and ROS generation and GSH deletion may play a key role in the radiosensitizing effect of docetaxel.

Antitumor efficacy of lidamycin on hepatoma and active moiety of its molecule

To study the in vitro and in vivo antitumor effect of lidamycin (LDM) on hepatoma and the active moiety of its molecule. MTT assay was used to determine the growth inhibition of human hepatoma BEL-7402 cells, SMMC-7721 cells and mouse hepatoma H22 cells. The in vivo therapeutic effects of lidamycin and mitomycin C were determined by transplantable hepatoma 22 (H22) in mice and human hepatoma BEL-7402 xenografts in athymic mice. In terms of IC(50) values, the cytotoxicity of LDM was 10 000-fold more potent than that of mitomycin C (MMC) and adriamycin (ADM) in human hepatoma BEL-7402 cells and SMMC-7721 cells. LDM molecule consists of two moieties, an aproprotein (LDP) and an enediyne chromophore (LDC). In terms of IC(50) values, the potency of LDC was similar to LDM. However, LDP was 10(5)-fold less potent than LDM and LDC to hepatoma cells. For mouse hepatoma H22 cells, the IC(50) value of LDM was 0.025 nmol/L. Given by single intravenous injection at doses of 0.1, 0.05 and 0.025 mg/kg, LDM markedly suppressed the growth of hepatoma 22 in mice by 84.7%, 71.6% and 61.8%, respectively. The therapeutic indexes (TI) of LDM and MMC were 15 and 2.5, respectively. By 2 iv. injections in two experiments, the growth inhibition rates by LDM at doses of 0.1, 0.05, 0.025, 0.00625 and 0.0125 mg/kg were 88.8-89.5%, 81.1-82.5%, 71.2-74.9%, 52.3-59.575%, and 33.3-48.3%, respectively. In comparison, MMC at doses of 5, 2.5, and 1.25 mg/kg inhibited tumor growth by 69.7-73.6%, 54.0-56.5%, and 31.5-52.2%, respectively. Moreover, in human hepatoma BEL-7402 xenografts, the growth inhibition rates by LDM at doses of 0.05 mg/kg X2 and 0.025 mg/kg X2 were 68.7% and 27.2%, respectively. However, MMC at the dose of 1.25 mg/kg X2 showed an inhibition rate of 34.5%. The inhibition rate of tumor growth by LDM was higher than that by MMC at the tolerated dose. Both LDM and its chromophore LDC display extremely potent cytotoxicity to hepatoma cells. LDM shows a remarkable therapeutic efficacy against murine and human hepatomas in vivo.

Proteomic analysis of differential protein expression in a human hepatoma revertant cell line by using an improved two-dimensional electrophoresis procedure combined with matrix assisted laser desorption/ionization-time of flight-mass spectrometry.

The proteomic profiles of a human hepatoma revertant, CL1, and its original cell line, SMMC7721, were compared by using an improved two-dimensional electrophoresis (2-DE) procedure, with multi-IPGstrips gels (length <or= 13 cm) run simultaneously on one sodium dodecyl sulfate (SDS) gel (shortened MSOG method). Nineteen proteins, showing significant difference in expression (P < 0.01), were selected and identified by matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and database search. In the revertant CL1 cells, compared to human hepatoma SMMC7721 cells, upregulated expression levels of some proteins related to tumor suppression, like maspin, were found, whereas some proteins related to tumor growth, like cathepsin D, were downregulated. These facts suggest that the phenotypic reversion of the CL1 cells was at least partially due to changes at the translational level of the proteins which favored the reconstruction of the normal phenotype of the cell.

Preparation and characteristics of DNA-nanoparticles targeting to hepatocarcinoma cells.

To prepare thymidine kinase gene (TK gene) nanoparticles and to investigate the expression of TK gene. Poly(D,L-lactic-co-glycolic acid) (PLGA), a biodegradable and biocompatible polymer, was used to prepare recombinant plasmid P(EGFP-AFP) nanoparticles by a double-emulsion evaporation technique. Characteristics of the nanoparticles were investigated in this study, including morphology, entrapment efficiency, and tissue distribution. The expression of TK gene was also investigated by MTT assay, by which the viable cells were determined after the addition of ganciclovir (GCV). The enhanced green fluorescent protein (EGFP) expression in human hepatocellular carcinoma SMMC-7721 cells and normal parenchymal Chang liver cells were assessed by flow cytometry. The prepared plasmid-nanoparticles had regular spherical surface and narrow particle size span with a mean diameter of 72+/-12 nm. The mean entrapment efficiency was 91.25%. A total of 80.14% DNA was found to be localized in the livers after 1-h injection with (32)P-DNA-PLGA nanoparticles in mouse caudal vein. The expression of DNA encapsulated in nanoparticles was much higher than that in naked DNA, and human hepatocellular carcinoma SMMC-7721 cells were more sensitive to GCV than human normal parenchymal Chang liver cells. The enhanced transfection efficiency and stronger ability to protect plasmid DNA from being degraded by nucleases are due to nanoparticles encapsulation.

Growth arrest and apoptosis of human hepatocellular carcinoma cells induced by hexamethylene bisacetamide.

To investigate the cellular effects of hybrid polar compound hexamethylene bisacetamide (HMBA) on the growth and apoptosis of human hepatocellular carcinoma cells and to provide the molecular mechanism for potential application of HMBA in the treatment of liver cancer. Effects of HMBA on the growth of human hepatocellular carcinoma SMMC-7721 cells were assayed by MTT chronometry. Apoptosis induced by HMBA was detected by phase-contrast microscopy, flow cytometry, propidium iodide staining and immunocytochemical analysis. The growth of SMMC-7721 cells was significantly inhibited by HMBA, and the growth inhibitory rate was 51.1%, 62.6%, 68.7% and 73.9% respectively after treatment with 5.0, 7.5, 10.0 and 12.5 mmol/L of HMBA. In the cells treated with 10 mmol/L of HMBA for 72 h, the population of cells at sub-G(1) phase significantly increased, and the apoptotic bodies and condensed nuclei were detected. Moreover, treatment of SMMC-7721 cells with 10 mmol/L of HMBA down-regulated the expression of Bcl-2 anti-apoptotic protein, while slightly up-regulated the level of pro-apoptotic protein Bax. Treatment with 10.0 mmol/L of HMBA can significantly inhibit the growth and induce apoptosis of human hepatocellular carcinoma SMMC-7721 cells by decreasing the ratio of Bcl-2 to Bax.

Down-modulation of heat shock protein 70 and up-modulation of Caspase-3 during schisandrin B-induced apoptosis in human hepatoma SMMC-7721 cells.

To investigate the effect of schisandrin B (Sch B) on proliferation and apoptosis of human hepatoma SMMC-7721 cells in vitro and regulation of Hsp70 and Caspases-3, 7, 9 expression by Sch B. Human hepatoma cell line SMMC-7721 was cultured and treated with Sch B at various concentrations. Growth suppression was detected with MTT colorimetric assay. Cell apoptosis was confirmed by DNA ladder detection and flow cytometric analysis. The expression of Hsp70, Caspases-3, 7, 9 were analyzed by Western blot analysis. Sch B inhibited the growth of hepatoma SMMC-7721 cells in a dose-dependent manner, leading to a 50% decrease in cell number (LC50) value of 23.50 mg/L. Treatment with Sch B resulted in degradation of chromosomal DNA into small internucleosomal fragments, evidenced by the formation of a 180-200 bp DNA ladder on agarose gels. FCM analysis showed the peak areas of subdiploid at the increased concentration of Sch B. The results of Western bolt analysis showed that Hsp70 was down-regulated and Caspase-3 was up-regulated, while the activity of Caspases-7, -9 had no significant change. Sch B is able to inhibit the proliferation of human hepatoma SMMC-7721 cells and induce apoptosis, which goes through Caspase-3-dependent and Caspase-9-independent pathway accompanied with the down-regulation of Hsp70 protein expression at an early event.

Transforming growth factor-β1 stimulated protein kinase B serine-473 and focal adhesion kinase tyrosine phosphorylation dependent on cell adhesion in human hepatocellular carcinoma SMMC-7721 cells

Transforming growth factor-β1 (TGF-β1) is a potent growth inhibitor and apoptosis inducer for most normal cells. However, tumor cells are commonly nevertheless sensitive to the tumor-suppressing effects of TGF-β1. In this paper, we focus on the effects of TGF-β1 on two important anti-apoptotic protein kinases, protein kinase B (PKB), and focal adhesion kinase (FAK), in SMMC-7721 cells. We found that PKB-Ser-473 phosphorylation was apparently up-regulated by TGF-β1. In the meantime, PKB-Thr-308 phosphorylation was slightly up-regulated by TGF-β1. TGF-β1 could also enhance FAK-Tyr phosphorylation. We observed that integrin-linked kinase (ILK) was also up-regulated by TGF-β1 in good accordance with PKB-Ser-473 phosphorylation. We first found that TGF-β1 could stimulate PKB-Ser-473 phosphorylation possibly via up-regulating ILK expression. Furthermore, we also failed to detect PKB-Ser-473 and FAK-Tyr phosphorylation with various concentrations of TGF-β1 treatment when cells were kept in suspension. The above results indicate that PKB-Ser-473 and FAK-Tyr phosphorylation stimulated by TGF-β1 are both dependent on cell adhesion.

TGF-beta1-promoted epithelial-to-mesenchymal transformation and cell adhesion contribute to TGF-beta1-enhanced cell migration in SMMC-7721 cells.

Transforming growth factor-b1 (TGF-beta1), a multi-function polypeptide, is a double-edged sword in cancer. For some tumor cells, TGF-beta1 is a potent growth inhibitor and apoptosis inducer. More commonly, TGF-beta1 loses its growth-inhibitory and apoptosis-inducing effects, but stimulates the metastatic capacity of tumor cells. It is currently little known about TGF-beta1-promoted cell migration in hepatocellular carcinoma (HCC) cells, let alone its mechanism. In this study, we found that TGF-beta1 lost its tumor-suppressive effects, but significantly stimulated cell migration in SMMC-7721 human HCC cells. By FACS and Western blot analysis, we observed that TGF-beta1 enhanced the expression of alpha5beta1 integrin obviously, and subsequently stimulated cell adhesion onto fibronectin (Fn). Furthermore, we observed that TGF-beta1 could also promote SMMC-7721 cells adhesion onto laminin (Ln). Our data also provided evidences that TGF-beta1 induced epithelial-to-mesenchymal transformation (EMT) in SMMC-7721 cells. First, SMMC-7721 cells clearly switched to the spindle shape morphology after TGF-beta1 treatment. Furthermore, TGF-beta1 induced the down-regulation of E-cadherin and the nuclear translocation of beta-catenin. These results indicated that TGF-beta1-promoted cell adhesion and TGF-beta1-induced epithelial-to-mesenchymal transformation might be both responsible for TGF-beta1-enhanced cell migration.

Effects of tachyplesin on the regulation of cell cycle in human hepatocarcinoma SMMC-7721 cells.

To investigate the effects of tachyplesin on the cell cycle regulation in human hepatcarcinoma cells. Effects of tachyplesin on the cell cycle in human hepatocarcinoma SMMC-7721 cells were assayed with flow cytometry. The protein levels of p53, p16, cyclin D1 and CDK4 were assayed by immunocytochemistry. The mRNA levels of p21(WAF1/CIP1) and c-myc genes were examined with in situ hybridization assay. After tachyplesin treatment, the cell cycle arrested at G0/G1 phase, the protein levels of mutant p53, cyclin D1 and CDK4 and the mRNA level of c-myc gene were decreased, whereas the levels of p16 protein and p21(WAF1/CIP1) mRNA increased. Tachyplesin might arrest the cell at G0/G1 phase by upregulating the levels of p16 protein and p21(WAF1/CIP1) mRNA and downregulating the levels of mutant p53, cyclin D1 and CDK4 proteins and c-myc mRNA, and induce the differentiation of human hepatocacinoma cells.

Docetaxel inhibits SMMC-7721 human hepatocellular carcinoma cells growth and induces apoptosis.

To investigate the in vitro anti-hepatocellular carcinoma (HCC) activity of docetaxel against SMMC-7721 HCC cells and its possible mechanism. The HCC cells were given different concentrations of docetaxel and their growth was measured by colony forming assay. Cell cycle and apoptosis were analyzed by flow cytometry and fluorescence microscopy (acridine orange/ethidium bromide double staining, AO/EB), as well as electronic microscopy. The SMMC-7721 HCC cell reactive oxygen species (ROS) and glutathione (GSH) were measured after given docetaxel. Docetaxel inhibited the hepatocellular carcinoma cells growth in a concentration dependent manner with IC(50) 5 x 10(-10)M. Marked cell apoptosis and G2/M phase arrest were observed after treatment with docetaxel >=10(-8)M. Docetaxel promoted SMMC-7721 HCC cells ROS generation and GSH deletion. Docetaxel suppressed the growth of SMMC-7721 HCC cells in vitro by causing apoptosis and G2/M phase arrest of the human hepatoma cells, and ROS and GSH may play a key role in the inhibition of growth and induction of apoptosis.

Expression of IGF-II in early experimental hepatocellular carcinomas and its significance in early diagnosis.

To investigate the serum level and expression of insulin growth factor II (IGF-II) in liver tissues of rats with early experimental hepatocellular carcinomas (HCC) and its significance in early diagnosis. Early experimental hepatocellular carcinomas were induced by diethylnitrosamine (DENA) in 180 male SD rats. Another 20 male SD rats served as control. The IGF-II serum level was measured by ELISA. Immunohistochemistry and electron microscopic immunohistochemistry were used to observe the expression of IGF-II in normal and tumor liver tissues and its ultrastructural location in malignant hepatocytes. The expressions of IGF-II in human hepatoma cell lines HepG2, SMMC7721 and human embryonic liver cell line L-02 were measured by immunocytochemistry. IGF-II mRNA level was studied by in situ hybridization. IGF-II was expressed in the cytoplasm of both sinusoidal cells in paracancerous cirrhotic liver tissue and malignant hepatocytes in early experimental HCC tissues. Gold particles were seen on the rough endoplasmic reticulum and the mitochondrion in malignant hepatocytes. IGF-II was expressed in the human hepatoma cell lines. The mRNA level of IGF-II was higher in rat liver tumor tissue than in normal rat liver tissue. The serum IGF-II level of the early experimental HCC group was 34.67+/-10.53 ng.ml(-1) and that of the control group was 11.75+/-5.84 ng.ml(-1). The rank sum test was used for statistical analysis. There was a significant difference between the two groups (P<0.01). During the induction of early experimental HCC by DENA, IGF-II may promote hepatocytic proliferation via a paracrine mechanism in the pre-cancerous stage. When hepatocytes are transformed into malignant cells, they may secrete IGF-II and promote malignant cell proliferation by an autocrine mechanism. IGF-II may be a possible biological marker in the early diagnosis of HCC.

Effects of tachyplesin on proliferation and differentiation of human hepatocellular carcinoma SMMC-7721 cells.

To investigate the antitumor activities of tachyplesin on human hepatocellular carcinoma (HCC) cells. Tachyplesin, isolated from acid extracts of Chinese horseshoe crab (Tachypleus tridentatus) hemocytes, was used to treat the human HCC cell line SMMC-7721. Effects of tachyplesin on the proliferation of SMMC-7721 cells were measured with trypan blue dye exclusion test and HE staining. The morphology and ultrastructure of the cells were examined by light microscopy and transmission electron microscopy, respectively. The activities of gamma-glutamyltransferase (gamma-GT) and tyrosine aminotransferase (TAT) were assayed with biochemical methods. The levels of alpha fetoprotein (alpha-FP), proliferating cell nuclear antigen (PCNA), p21( WAF1/CIP1) and c-myc were examined by immunocytochemistry. After treatment with tachyplesin 3.0 mg/L, the proliferation of SMMC-7721 cells was inhibited significantly, with the cell growth inhibitory rate amounted to 55.57 % and the maximum cell mitotic index declined by 43.68 %. The morphology and ultrastructure underwent restorational alteration. The activity of gamma-GT declined while TAT activity increased obviously, and the levels of alpha-FP and PCNA decreased. Moreover, the expression of p21(WAF1/CIP1) protein was up-regulated and that of c-myc protein was down-regulated. Tachyplesin could effectively inhibit the proliferation of hepatocarcinoma cells, reverse the malignant morphological and ultrastructural characteristics, alter the levels of enzymes and antigens, regulate the expression of differentiation-associated oncogene and tumor suppressor gene, and induce hepatocarcinama cell differentiation.

Over expression of integrin alpha 5 beta 1 in human hepatocellular carcinoma cell line suppresses cell proliferation in vitro and tumorigenicity in nude mice.

Integrin alpha 5 beta 1 and alpha 2 beta 1 are the major integrin receptors in human hepatocytes. However, in human hepatocellular carcinoma cells it was found that the expression of integrin alpha 5 beta 1 was decreased and another integrin alpha 6 beta 1 increased. In this study, the SMMC7721 human hepatocellular carcinoma cells cotransfected or singly transfected with integrin alpha 5 and/or beta 1 cDNAs were established, and designated alpha 5 beta 1.6-7721, alpha 5.3-7721, and beta 1.6-7721 cell lines, respectively. Transfection with cDNAs of integrin alpha 5 and beta 1 subunits resulted in the over expression of each integrin and modified biological properties, including a slowed growth rate, changes in the cell cycle from 15.5% of control cells in the G2/M phase to 12.1%, 9.6% and 9.4% in alpha 5.3-7721, beta 1.6-7721, alpha 5 beta 1.6-7721, respectively, and a decrease in the Cell Mitosis Index from 1.6 in controls to 0.96, 0.95, and 0.72, and 34%, 28% and 52% derived from colony forming ability, respectively. Tumorigenicity was also tested in nude mice with inoculation of cells subcutaneously. Tumor masses growing in nude mice following inoculation with beta 1.6-7721, and alpha 5 beta 1.6-7721 cells weighed only 52% or 31% those of control cells. These results indicated that deletion or low expression of integrin alpha 5 beta 1 may play an important role in the development of hepatocellular carcinoma. Therefore, induction of expression of the integrin alpha 5 beta 1 in malignant cells could be a potential means of treating hepatocellular carcinoma.

Growth induction of hepatic stimulator substance in hepatocytes through its regulation on EGF receptors.

The cytosolic liver-specific growth factor-hepatic stimulator substance (HSS) has been shown to be able to amplify the rat hepatocyte proliferation responded to EGF. In order to get more insight into the mechanism, the regulatory effect of HSS on EGF-receptor (EGF-R) and the receptor phosphorylation at molecular level was studied. HSS partially purified from weanling rat liver was given to cultured hepatocytes and its influence on EGF-R specific binding and internalization as well as mRNA expression were investigated. The results showed that preincubation of hepatocytes with HSS could lead to an increase in [125I]-EGF binding to its receptors and inhibit EGF-induced receptor down-regulation. Furthermore, the over-expression of EGF-R mRNA stimulated by HSS was seen during 2-12 h after the incubation. Additionally, it was demonstrated with human hepatoma SMMC-7721 cells in Western blot that the EGF-R expression and the receptor autophosphorylation were increased with dose/time-dependency after HSS treatment. These results strongly suggest that the mechanism of HSS action on hepatocyte growth might be related to its modulation on EGF-R and receptor-mediated signaling transduction.

Inhibitory activity of polysaccharide extracts from three kinds of edible fungi on proliferation of human hepatoma SMMC-7721 cell and mouse implanted S180 tumor.

AIM:To determine the activities of polysaccharide extracts from Flammulina velutipes (Curt. ex Fr.) Sing (FV), Lentinus edodes (LE)and Agaricus bispo-rus Sing (AB) on the proliferation of human hepatoma SMMC-7721 cells in vitro and on mouse implanted S-180 tumors in vivo.METHODS:The polysaccharide extracts were isolated from the fruit bodies of FV, LE and AB by the methods of hot-water extraction,Sevag's removal of proteins, ethanol precipitation, trypsin digestion and ethanol fractional precipitation. Human hepatoma SMMC-7721 cells were treated with 50mg/L polysaccharide extracts, and the mitosis index, mitochondria activity and cell proliferation were detected at different times in both control and experimental groups. The mice with S-180 implanted tumors were injected with the polysaccharide extracts at 24mg/kg body weight for 9d and the tumor weight was measured on the 15th day.RESULTS:The mitosis index of hepatoma cells in vitro could be significantly decreased by treatment with the polysaccharide extracts from the three kinds of edible fungi (P< 0.005). The cell numbers and mitochondria activity of SMMC-7721 cells treated with polysaccharide extracts were lower than those in control groups (P<0.005). The inhibition rates of polysaccharide extracts against implanted S-180 tumors in mice were 52.8%, 56.6% and 51.9% respectively compared with that in control groups.CONCLUSION:The polysaccharide extracts from the three kinds of edible fungi could inhibit not only the cultured malignant cells in vitro but also implanted S-180 tumor in vivo.