Negatively regulating mechanism of Sirpal in hepatocellular carcinoma:an experimental study

BACKGROUND: Signal regulatory protein ( Sirp) is a recently isolated, cloned and identified inhibitor receptor distributed in the membrane of hematopoietic and nonhema-topoietic cells. Sirp alphal ( Sirpα1) is a member of Sirp families. Sirpal can bind SHP-2 in the form of tyrosine phosphorylation by SH2 effect and negatively regulate growth factor, oncogene, or insulin-induced responses as its substrate. This study aimed to preliminarily clarify the negatively regulating proliferation mechanism of Sirpal in liver cancer. METHODS: pLXSN, Sirpα1 and Sirpα1Δ4Y2 plasmids were respectively transfected into Sk-Hepl liver cancer cell line, and various stable Sk-Hepl cell lines were obtained with screening agent of G418 (1200 μg/ml). The expressing levels of cyclin D1, CDK4, Fas, β-catenin and gankyrin in various cell lines were determined with Western blotting. Cell cycles were determined at 0, 12 and 24 hours with flow cytotnetry after various synchronous cell lines were cultured without serum for 72. Cell apoptosis induced with agent of TNF-α (50 ng/ml) was determined with flow cytotnetry at 0,0.5,1,3,6 and 12 hours. RESULTS: Sirpα1 could significantly decrease the expression of cyclin D1, β-catenin and gankyrin, but it couldn't affect the expression level of CDK4 and Fas. When synchronous cells were cultured for 12 hours, S phase Sk-Hep1 cell transfected with Sirpal plasmid was the lowest [(31.92 ± 0.22)% vs. other cell lines, P <0.05], and the cell line was highly sensitive to TNF-α agent for 1 hour. (59.31 ±0.59)% of apoptotic cells occurred (vs. the other time points, P < 0.05). CONCLUSIONS: Sirpal might block the cell cycle of liver cancer, inhibit cell proliferation, promote cell apoptosis by decreasing the expression of cyclin D1, β-catenin and gankyrin. It is one of the important mechanisms inhibiting the occurrence and development of hepatocellular carcinoma.     

CADM1 regulates the G1/S transition and represses tumorigenicity through the Rb-E2F pathway in hepatocellular carcinoma

BACKGROUND: Increasing evidence indicates that down-regulation of cell adhesion molecule 1 (CADM1) contributes to tumorigenesis in various cancers. The present study was undertaken to investigate the CADM1 expression pattern in human hepatocellular carcinoma (HCC), and to elucidate the mechanism underlying CADM1-mediated tumor suppression.
METHODS: CADM1 expression in HCC cell lines was mea-sured by quantitative real-time PCR. The function of CADM1 in the context of tumor suppression in HCC cells was deter-mined using proliferation assays, cell cycle analysis, EdU in-corporation assays,in vitro colony formation analysis, andin vivo tumorigenicity assays. The mechanism by which CADM1 acts as a tumor suppressor gene in HCC was investigated us-ing Western blotting analysis.
RESULTS: Downregulation of CADM1 expression is fre-quently detected in both HCC cells and clinical samples. Res-toration of CADM1 expression in HCC cell lines signiifcantly inhibits cell growth and negatively regulates the G1/S transi-tion. CADM1 overexpression can inhibit the tumorigenicity of HCC cells bothin vitro andin vivo. Western blotting analysis revealed that ectopic expression of CADM1 in HCC cells is associated with increased expression of Retinoblastoma (Rb) protein.
CONCLUSIONS: Our results showed that suppression of tu-morigenesis by CADM1 may be mediated by the Rb-E2F path-way, involving upregulation of Rb protein levels. This pathway could therefore represent an attractive target for HCC therapy.     

Down-regulation of PTEN expression due to loss of promoter activity in human hepatocellular carcinoma cell lines

AIM: To investigate the regulation of phosphatase and tensin homolog deleted on chromosome ten (PTEN) gene expression in human hepatocellular carcinoma (HCC) cell lines. METHODS: The mRNA and protein levels of PTEN were detected by Northern blot and Western blot in HCC cell lines, respectively. Plasmids containing different fragments of PTEN promoter with Luciferase reporter were constructed and transiently transfected into HCC cell lines to study the promoter activity. DNA analysis and RT-PCR were performed to detect the mutation of PTEN promoter and PTEN cDNA. RESULTS: Either protein or mRNA levels of PTEN in L02 cells (as a control) were significantly higher than that in HCC cell lines. The profile of PTEN promoter activity in 8 cell lines was closely correlated with levels of PTEN mRNA and PTEN protein. Furthermore, the sequence analysis of 8 cells lines showed no mutation in the region of PTEN promoter and PTEN cDNA. CONCLUSION: PTEN expression is down-regulated in HCC cell lines probably due to loss of activity of PTEN promoter.     

Effects and mechanism of miR-214 on hepatocellular carcinoma

Objective:To explore the role of miR-214 in the progression of hepatocellular carcinoma(HCC) and its inhibitory mechanisms in depressing the signaling pathway of j3-catenin.this study was conducted.Methods:We ectopically expressed miR-214 in HepG2 cells to obtain cell lines Lv-miR-214-HepG2 and their control Lv-control-HepG2.Differences between the two cell lines were compared in cell growth,proliferation,colony forming ability and cell cycles.RT-PCR method was applied for the quantification of β-catenin mRNA expression.Western-blot method was applied for the determination of the protein level of β-catenin and their downstream targets(ie.Cyclin D1,c-Myc and TCF-1).The effect of miR-214 on cells was further explored through RNA interference and restoring miR-214 expression.Results:In comparison with negative(Lv-control-HepG2) and blank(HepG2) control,a significant inhibition of cell growth and proliferation caused by miR-214 was observed after 48~72h of cell culture experiments(P0.05).The miR-214 treatment resulted in a colony forming efficiency of(23.28±3.26)%,which was significantly lower than that of negative control[(51.31±3.97)%](P0.05).According to FCM results,the experimental group,compared with control,showed a higher proportion of cells in G_0/G_1 phase[(70.32±3.12)%]but a lower proportion in S phase[(18.42±2.90)%](P0.05).The MTT assay demonstrated a significant inhibition of the proliferation and β-catenin expression of HCC cells compared with control(P0.05).while no significant difference was observed after HCC cells being transfected withβ-catenin overexpression plasmid(P0.05).By comparing to the RT-PCR and Western-blot results of control,the miR-214 treatment led to a slightly decrease in the β-catenin mRNA expression(P0.05).but an extremely inhibition in the protein level of β-catenin and its downstream targets Cyclin Dl,c-Myc.and TCF-1(P0.05).Conclusions:miR-214 functions as a suppressor during the progression of HCC,and its inhibitory role was achieved by downregulating β-catenin signaling pathway.     

Degradation of retinoid X receptor α by TPA through proteasome pathway in gastric cancer cells

AIM: To investigate and determine the mechanism and signal pathway of tetradecanoylphorbol-1, 3-acetate (TPA) in degradation of RXRα.METHODS: Gastric cancer cell line, BGC-823 was used in the experiments. The expression level of R XRα protein was detected by Western blot. Nuclear and cytoplasmic protein fractions were prepared through lysis of cell and centrifugation.Localization and translocation of RXRα were observed under laser-scanning confocal microscope through labeling specific anti-RXRα antibody and corresponding immunofiuorescent antibody as secondary antibody. Different inhibitors were used as required.RESULTS: In BGC-823 cells, RXRα was expressed in the nucleus. When cells were treated with TPA, expression of RXRα was repressed in a time-dependent and TPAconcentration-dependent manner. Meanwhile, translocation of RXR from the nucleus to the cytoplasm occurred, also in a time-dependent manner. When cells were pre-incubated with proteasome inhibitor MG132 for 3 hrs, followed by TPA for another 12 hrs, TPA-induced RXRα degradation was inhibited. Further observation of RXRα translocation in the presence of MG132 showed that MG-132 could block TPAinduced RXRα redistribution. Conversely, when RXRαtranslocation was inhibited by LMB, an inhibitor for blocking protein export from the nucleus, TPA could not repress expression of RXRα.CONCLUSION: TPA could induce the degradation of RXRα protein in BGC-823 cells, and this degradation is time-and TPA-concentration-dependent. Furthermore, the degradation of RXRα by TPA is via a proteasome pathway and associated with RXRα translocation from the nucleus to the cytoplasm.     

Degradation of retinoid X receptor α by TPA through proteasome pathway in gastric cancer cells

AIM: To investigate and determine the mechanism and signal pathway of tetradecanoylphorbol-1, 3-acetate (TPA) in degradation of RXRα.METHODS: Gastric cancer cell line, BGC-823 was used in the experiments. The expression level of RXRα protein was detected by Western blot. Nuclear and cytoplasmic protein fractions were prepared through lysis of cell and centrifugation.Localization and translocation of RXRcz were observed under laser-scanning confocal microscope through labeling specific anti-RXRα antibody and corresponding immunofluorescent antibody as secondary antibody. Different inhibitors were used as required.RESULTS: In BGC-823 cells, RXRα was expressed in thenucleus. When cells were treated with TPA, expression of RXRα was repressed in a time-dependent and TPA-manner. Meanwhile, translocation of RXRα from the nudeus to the cytoplasm occurred, also in a time-dependent manner. When cells were pre-incubated with proteasome inhibitor MG132 for 3 hrs, followed by TPA for another 12 hrs, TPA-induced RXRα degradation was inhibited. Further observation of RXRα translocation in the presence of MG132 showed that MG-132 could block TPA-induced RXRα redistribution. Conversely, when RXRα translocation was inhibited by LMB, an inhibitor for blocking protein export from the nucleus, TPA could not repress expression of RXRα.CONCLUSION:TPA could induce the degradation of RXRα protein in BGC-823 cells,and this degradation is time-and TPA-concentration-dependent.Furthermore,the degradation of RXRα by TPA is via a proteasome pathway and associated with RXRα transiocation from the nucleus to the cytoplasm.     

Overexpression of DNA methyltransferase 1 and its biological significance in primary hepatocellular carcinoma

AIM： To explore the relationship between DNA methyltransferase 1 （DNMT1） and hepatitis B virus （HBV）-related hepatocellular carcinoma （HCC） and its biological significance in primary HCC. METHODS： We carried out an immunohistochemical examination of DNMT1 in both HCC and paired nonneoplastic liver tissues from Chinese subjects. DNMT1 mRNA was further examined in HCC cell lines by real-time PCR. We inhibited DNMT1 using siRNA and detected the effect of depletion of DNMT1 on cell proliferation ability and cell apoptosis in the HCC celt line SMMC-7721. RESULTS： DNMT1 protein expression was increased in HCCs compared to histologically normal nonneoplastic liver tissues and the incidence of DNMT1 immunoreactivity in HCCs correlated significantly with poor tumor differentiation （P = 0.014）. There were more cases with DNMT1 overexpression in HCC with HBV （42.85%） than in HCC without HBV （28.57%）. However, no significant difference in DNMT1 expression was found in HBV-positive and HBV-negative cases in the Chinese HCC group. There was a trend that DNMT1 RNA expression increased more in HCC cell lines than in pericarcinoma cell lines and normal liver cell lines. In addition, we inhibited DNMT1 using siRNA in the SMMC-7721 HCC cell line and found depletion of DNMT1 suppressed cells growth independent of expression of proliferating cell nuclear antigen （PCNA）, even in HCC cell lines where DNMT1 was stably decreased. CONCLUSION： The findings implied that DNMT1 plays a key role in HBV-retated hepatocellular tumorigenesis. Depletion of DNMT1 mediates growth suppression in SMMC-7721 cells.     

Annexin A1: A new immunohistological marker of cholangiocarcinoma

AIM: To evaluate a new immunohistological marker, annexin A1 (ANXA1), in cholangiocarcinoma (CCA) and hepatocellular carcinoma (HCC). METHODS: Expression of ANXA1 protein was investigated in liver tissues from patients with CCA and HCC by immunohistochemistry. Its expression on differences stages of tumor development was investigated in hamster CCA tissues induced by Opisthorchis viverrini and N -nitrosodimethylamine. Moreover, mRNA expression of ANXA1 was assessed in CCA cell lines by quantitative real-time polymerase chain reaction and silencing of ANXA1 gene expression using small interfering RNA. RESULTS: In human CCA tissue arrays, immunohistochemical analysis revealed that the positive expression of ANXA1 was 94.1% (64/68 cases) consisting of a high expression (66.2%, 45/68 cases) and a low expression (33.8%, 23/68 cases). However, expression of ANXA1 protein was negative in all histologic patterns for HCC (46/46 cases) and healthy individuals (6/6 cases). In hamster with opisthorchiasis-associated CCA, the expression of ANXA1 was observed in the cytoplasm of inflammatory cells, bile duct epithelia and tumor cells. Grading scores of ANXA1 expression were significantly increased with tumor progression. In addition, mRNA expression of ANXA1 significantly increased in all of the various CCA cell lines tested compared to an immortalized human cholangiocyte cell line (MMNK1). Suppressing the ANXA1 gene significantly reduced the matrix metalloproteinase (MMP) 2 and MMP9, and transforming growth factor-β genes, but increased nuclear factor-kB gene expression. CONCLUSION: ANXA1 is highly expressed in CCA, but low in HCC, suggesting it may serve as a new immunohistochemical marker of CCA. ANXA1 may play a role in opisthorchiasis-associated cholangiocarcinogenesis.     

Annexin A2 silencing inhibits invasion,migration, and tumorigenic potential of hepatoma cells

AIM: To investigate the effects of Annexin A2 (ANXA2) silencing on invasion, migration, and tumorigenic potential of hepatoma cells. METHODS: Human hepatoma cell lines [HepG2, SMMC-7721, SMMC-7402, and MHCC97-H, a novel human hepatocellular carcinoma (HCC) cell line with high metastasis potential] and a normal hepatocyte cell line(LO2) were used in this study. The protein and mRNA expression levels of ANXA2 were analysed by western blotting and real-time polymerase chain reaction, re-spectively. The intracellular distribution profile of ANXA2 expression was determined by immunofluorescence and immunohistochemistry. Short hairpin RNA target-ing ANXA2 was designed and stably transfected into MHCC97-H cells. Cells were cultured for in vitro analy-ses or subcutaneously injected as xenografts in mice for in vivo analyses. Effects of ANXA2 silencing on cell growth were assessed by cell counting kit-8 (CCK-8) as-say (in vitro ) and tumour-growth assay (in vivo ), on cell cycling was assessed by flow cytometry and propidium iodide staining (in vitro ), and on invasion and migration potential were assessed by transwell assay and wound-healing assay, respectively (both in vitro ). RESULTS: The MHCC97-H cells, which are known to have high metastasis potential, showed the highest lev-el of ANXA2 expression among the four HCC cell types examined; compared to the LO2 cells, the MHCC97-H expression level was 8-times higher. The ANXA2 expres-sion was effectively inhibited (about 80%) by ANXA2-specific small hairpin RNA (shRNA). ANXA2 expression in the MHCC97-H cells was mainly localized to the cel-lular membrane and cytoplasm, and some localization was detected in the nucleus. Moreover, the proliferation of MHCC97-H cells was obviously suppressed by shR-NA-mediated ANXA2 silencing in vitro , and the tumour growth inhibition rate was 38.24% in vivo . The per-centage of MHCC97-H cells in S phase dramatically de-creased (to 27.76%) under ANXA2-silenced conditions. Furthermore, ANXA2-silenced MHCC97-H cells showed lower invasivenes     

Transfection of apoptosis related gene Fas ligand in human hepatocellular carcinoma cells and its significance in apoptosis

AIM: To evaluate the expression of apoptosis related gene Fas ligand (FasL) in human hepatocellular carcinoma (HCC) cells HepG2 and its significance in apoptosis. METHODS: Levels of soluble Fas ligand (sFasL) in a group of patients with hepatitis B virus (HBV)-induced chronic hepatitis, HBV-positive liver cirrhosis and HCC were evaluated. In a further study, the recombinant eukaryotic expression plasmid pcDNA3.1hisB-FasL was transfected into HCC cells HepG2 by lipofection, and then soluble FasL was examined in the supernatant of culture cells by EIA, FasL expression in HepG2 cells was detected by immuohistochemistry. After being stained by annexin V and propidium iodine, cells were passed through a flow cytometer and examined by a fluorescence microscope and a laser scanning microscope. RESULTS: The sFasL levels were significantly lower in patients with HCC when compared to the patients with hepatitis or liver cirrhosis. In comparison with untransfected cells, the soluble FasL could be detected in the supernatant of transfected cells. FasL was expressed on the membranes and cytoplasm of transfected cells. The apoptotic cell rate was 36.30% in transfected cells, and was 11.53% in untransfected cells. Moreover, the different stage of apoptotic cells could be distinguished by annexin V and propidium iodine staining. CONCLUSION: Fas ligand is an apoptotic pathway of HCC cells.     

CacyBP/SIP nuclear translocation induced by gastrin promotes gastric cancer cell proliferation

AIM:To investigate the role of nuclear translocation of calcyclin binding protein,also called Siah-1 interacting protein(CacyBP/SIP),in gastric carcinogenesis.METHODS:The expression of CacyBP/SIP protein in gastric cancer cell lines was detected by Western blot.Immunofluorescence experiments were performed on gastric cancer cell lines that had been either unstimulated or stimulated with gastrin.To confirm the immunofluorescence findings,the relative abundance of CacyBP/SIP in nuclear and cytoplasmic compartments was assessed by Western blot.The effect of nuclear translocation of CacyBP/SIP on cell proliferation was examined using MTT assay.The colony formation assay was used to measure clonogenic cell survival.The effect of CacyBP/SIP nuclear translocation on cell cycle progression was investigated.Two CacyBP/SIPspecific siRNA vectors were designed and constructed to inhibit CacyBP/SIP expression in order to reduce the nuclear translocation of CacyBP/SIP,and the expression of CacyBP/SIP in stably transfected cells was determined by Western blot.The effect of inhibiting CacyBP/SIP nuclear translocation on cell proliferation was then assessed.RESULTS:CacyBP/SIP protein was present in most of gastric cancer cell lines.In unstimulated cells,CacyBP/SIP was distributed throughout the cytoplasm;while in stimulated cells,CacyBP/SIP was found mainly in the perinuclear region.CacyBP/SIP nuclear translocation generated a growth-stimulatory effect on cells.The number of colonies in the CacyBP/SIP nuclear translocation group was significantly higher than that in the control group.The percentage of stimulated cells in G1phase was significantly lower than that of control cells(69.70%±0.46%and 65.80%±0.60%,control cells and gastrin-treated SGC7901 cells,P=0.008;72.99%±0.46%and 69.36%±0.51%,control cells and gastrin-treated MKN45 cells,P=0.022).CacyBP/SIPsi1effectively down-regulated the expression of CacyBP/SIP,and cells stably transfected by CacyBP/SIPsi1 were then chosen for further cellular assays.In CacyBP/SIPsi1 stably transfected cells,CacyBP/SIP was shown to be distributed throughout the cytoplasm,irregardless of whether they were stimulated or not.After CacyBP/SIP nuclear translocation was reduced,there had no major effect on cell proliferation,as shown by MTT assay.There had no enhanced anchoragedependent growth upon stimulation,as indicated by colony formation in flat plates.No changes appeared in the percentage of cells in G0-G1 phase in either cell line(71.09%±0.16%and 70.86%±0.25%,control cells and gastrin-treated SGC7901-CacyBP/SIPsi1 cells,P=0.101;74.17%±1.04%and 73.07%±1.00%,control cells and gastrin-treated MKN45-CacyBP/SIPsi1cells,P=0.225).CONCLUSION:CacyBP/SIP nuclear translocation promotes the proliferation and cell cycle progression of gastric cancer cells.     

Wortmannin influences hypoxia-inducible factor-1 alpha expression and glycolysis in esophageal carcinoma cells

AIM: To investigate the influence of phosphatidylinositol-3-kinase protein kinase B(PI3K/AKT)-HIF-1α signaling pathway on glycolysis in esophageal carcinoma cells under hypoxia. METHODS: Esophageal carcinoma cell lines Eca109 and TE13 were cultured under hypoxia environment, and the protein, m RNA and activity levels of hypoxia inducible factor-1 alpha(HIF-1α), glucose transporter 1, hexokinase-Ⅱ, phosphofructokinase 2 and lactate dehydrogenase-A were determined. Supernatant lactic acid concentrations were also detected. The PI3K/AKT signaling pathway was then inhibited with wortmannin, and the effects of hypoxia on the expression or activities of HIF-1α, associated glycolytic enzymes and lactic acid concentrations were observed. Esophageal carcinoma cells were then transfected with interference plasmid with HIF-1α-targeting si RNA to assess impact of the high expression of HIF-1α on glycolysis.RESULTS: HIF-1α is highly expressed in the esophageal carcinoma cell lines tested, and with decreasing levels of oxygen, the expression of HIF-1α and the associated glycolytic enzymes and the extracellular lactic acid concentration were enhanced in the esophageal carcinoma cell lines Eca109 and TE13. In both normoxia and hypoxic conditions, the level of glycolytic enzymesand the secretion of lactic acid were both reduced by wortmannin. The expression and activities of glycolytic enzymes and the lactic acid concentration in cells were reduced by inhibiting HIF-1α, especially the decreasing level of glycolysis was significant under hypoxic conditions.CONCLUSION: The PI3K/AKT pathway and HIF-1α are both involved in the process of glycolysis in esophageal cancer cells.     

Potential roles of EZH2, Bmi-1 and mi R-203 in cell proliferation and invasion in hepatocellular carcinoma cell line Hep3B

AIM: To investigate the potential roles of enhancer of zeste homolog2(EZH2), Bmi-1 and mi R-203 in cell proliferation and invasion in hepatocellular carcinoma(HCC) cell line Hep3 B.METHODS: A total of 73 patients who underwent surgical resection at Fuzong Clinical Medical College of Fujian Medical University were enrolled in this study. Hep3 B cells were cultivated in RPMI 1640 medium supplemented with 10% fetal bovine serum at 37?℃. Vectors that containing c DNA of the EZH2 gene or mi R-203 targeted sh RNA plasmid were constructed, and then transfected into Hep3 B cells. The m RNA expression of mi R-203, EZH2, and Bmi-1 was analyzed using quantitative real-time polymerase chain reaction analysis, and the protein levels of EZH2 and Bmi-1 were detected by Western blot analysis. Effect of EZH2 or mi R-203 on cell proliferation was observed by methyl thiazolyl tetrazolium assay, and cell apoptosis was assessed using flow cytometry. Besides, effect of EZH2 or mi R-203 on tumor cell invasion was detected using Transwell assay.RESULTS: The m RNA levels of EZH2 and Bmi-1 in HCC tissues and in Hep3 B cells were significantly higher compared with those in normal samples(P 0.01), while mi R-203 level was significantly lower in HCC tissues(P 0.01). Hep3 B cells transfected with EZH2-sh RNA or mi R-203-sh RNA showed lower expression levels of EZH2 and Bmi-1(P 0.05). Compared with controls, Hep3 B cells transfected with EZH2-sh RNA had relative slow cell proliferation, indicating that low expression of EZH2 and Bmi-1 and overexpression of mi R-203 could inhibit Hep3 B cell proliferation(P 0.05). The average apoptosis rate of Hep3 B cells transfected with EZH2-sh RNA vector was about 18.631%, while that of Hep3 B cells transfected with sh RNA vector was about 5.33%, suggesting that EZH2 was down-regulated by transfecting with EZH2-sh RNA, and the down-regulated EZH2 contributed to the cell apoptosis. Low expression of EZH2 and Bmi-1 and overexpression of mi R-203 could reduce Hep3 B cell invasion(P 0.05).CONCLUSION: Our study suggests that EZH2 and Bmi-1 are up-regulated while mi R-203 is downregulated in Hep3 B cells. Mi R-203 may contribute to the metastasis and enhance apoptosis of HCC cells by regulating EZH2 and Bmi-1. Our study may provide a theoretical basis for metastasis of HCC and targeted therapy of HCC.     

Roles of PLC-γ2 and PKCα in TPA-induced apoptosis of gastric cancer cells

AIM: To investigate the roles of PLCγ2 and PKCα in TPA-induced apoptosis of gastric cancer cells. METHODS: Human gastric cancer cell line MGCS0-3 was used. Protein expression levels of PLCγ2 and PKCα were detected by Western blot. Protein localization of PLCγ2 and PKCα was shown by immunofluoscence analysis under laser-scanning confocal microscope. Apoptotic morphology was observed by DAPI fluorescence staining, and apoptotic index was counted among I 000 cells randomly. RESULTS: Treatment of gastric cancer cells MGCS0-3 with TPA not only up-regulated expression of PLC-γ2 protein, but also induced PLC-γ2 translocation from the cytoplasm to the nucleus. However, this process was not directly associated with apoptosis induction. Further investigation showed that PKCa translocation from the cytoplasm to the nucleus was correlated with initiation of apoptosis. To explore the inevitable linkage between PLC-γ2 and PKCα during apoptosis induction, PLC inhibitor U73122 was used to block PLC-γ2 translocation,in which neither stimulating PKCα translocation nor inducing apoptosis occurred in MGC80-3 cells. However, when U73122-treated cells were exposed to TPA, not only PLC-γ2, but also PKCα was redistributed. On the other hand, when cells were treated with PKC inhibitor alone, PLC-γ2 protein was still located in the cytoplasm. However, redistribution of PLC-γ2 protein occurred in the presence of TPA, no matter whether PKC inhibitor existed or not. CONCLUSION: PLC-γ2 translocation is critical in transmittingTPA signal to its downstream molecule PKCα. As an effector, PKCα directly promotes apoptosis of MGC80-3 cells. Therefore, protein translocation of PLCγ2 and PKCα is critical event in the process of apoptosis induction.     

Subcellular daunorubicin distribution and its relation to multidrug resistance phenotype in drug—resistant cell line SMMC—7721／R

AIM：To investigate the correlation between subcellular daunorubicin distribution and the multidrug resistance phenotype in drug-resistant cell line SMMC-7721/R.METHODS:The multidrug resistant cell line SMMC-7721/R,a human hepatocellular carcinoma cell line,was established.Antisenes oligonucleotides(AS-ODN)were used to obtain different multidrug resistance phenotypes by inhibiting the expression of mdr1 gene and/or multidrug resistance-related protein gene(mrp)using Lipofectamine as delivery agent.Expression of mdr1 and mrp genes was evaluated by RT-PCRand Western blotting.Intracellular daunorubicn(DNR)concentration was measured by flow cytometry.Subcellular DNR distribution was analyzed by confocal laser scanning microscopy.Adriamycin(ADM)and DNR sensitivity was examined by MTTmethod.RESULTS:Low level expression of mdr1 and mrpmRNAs and no expression of P-Glycoprotein(P-gp)and multidrug resistance-related protein(P190)were detected in parental sensitive cells SMMC-7721/S,but over-expression of these two genes was observed in drug-resistant cell SMMC-7721/R,The expression of mdr1 and mrp genes in SMMC-7721/Rcells was down-regulated to the level in the SMMC-7721/Scells by AS-ODN.Intracellular DNAconcentration in SMMC-7721/Scells was 10times higher than that in SMMC-7721/Rcells.In SMMC7721/Scells intracellular DNA distributed evenly in the nucleus and cytoplasm.while in SMMC-7721/Rcells DNR distributed in a punctate pattern in the cytoplasm and was reduced in the nucleus.DNR concentration in SMMC-7721/Rcells co-transfected with AS-ODNs targeting to mdr1and rpmRNAs recovered to 25percent of that in SMMC7721/Scells.Intracellular DNA distribution pattern in drug-resistant cells treated by AS-ODN was similar to drug-sensitive cell.and the cells resistance index(RI)to DNA and AMD decreased at most from 88.0and 116.0to4.0and 2.3,repectively.Co-Transfection of two AS-ODNs showed a stronger synergistic effect than separate transfection.CONCLUSIONS:P-gp and P190are two members mediatingMDR in cellline SMMC7721/R,Intracellular drug concentration increase and subcellular distribution change are two important factos in multidrug resistance(MDR)formation.The second facto,drugs transport by P-gp andP190from cell nucleus to organell in cytoplasm,may play a more important role.