[Curcumin promotes apoptosis of esophageal squamous carcinoma cell lines through inhibition of NF-kappaB signaling pathway].

BACKGROUND & OBJECTIVE: Activation of NF-kappaB signaling pathway plays a critical role in the initiation and progression of carcinogenesis. However, the role of NF-kappaB pathway in esophageal squamous cell carcinoma (ESCC) has not been fully elucidated. Studies have shown that curcumin possesses anti-infection and anti-oxidation effects. This study was to evaluate whether curcumin could induce apoptosis through inhibition of NF-kappaB signaling pathway in ESCC cells. METHODS: Expressions of pIkappaBalpha and Bcl-2 were detected using Western blott after incubation of ESCC cells with curcumin (50 micromol/L) at different time points. Apoptosis and the number of viable ESCC cells were analyzed using flow cytometry and MTT, respectively, after the treatment of curcumin, 5-FU, or the combination of curcumin and 5-FU. RESULTS: In two ESCC cell lines, EC9706 and Eca109,curcumin inhibited IkappaBalpha phosphorylation and Bcl-2 in a time-dependent manner; curcumin alone increased cell apoptosis (P<0.05), and the effect became more prominent when it was combined with 5-FU (P<0.05); curcumin plus 5-FU exerted a stronger inhibition effect on cell proliferation than curcumin alone (P<0.05) or 5-FU alone (P<0.05). CONCLUSION: Curcumin inhibits the phosphorylation of IkappaBalpha, leading to suppression of proliferation, induction of apoptosis and an increase of the sensitivity of ESCC cell lines towards 5-FU.

[Expression of Notch1 gene in esophageal squamous cell carcinoma cell line EC9706 and its effect on cell apoptosis].

BACKGROUND & OBJECTIVE: Notch1 signaling pathway is closely associated with carcinogenesis and plays a key role in cell growth, proliferation, differentiation, and apoptosis. This study was to investigate the expression of Notch1 gene in esophageal squamous cell carcinoma (ESCC) cell line EC9706 and its effects on cell apoptosis. METHODS: The expression of Notch1 gene in EC9706 cells was detected by immunocytochemistry. Notch1 gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR). A eukaryotic expression vector pcDNA3.1-Notch1 (termed pcNICD) was constructed and transfected into EC9706 cells; pcDNA3.1 was also transfected as control. After transfection, the expression of Notch1 in EC9706 cells was detected by RT-PCR and Western blot, cell apoptosis was measured by flow cytometry (FCM). RESULTS: The expression of Notch1 gene was detected in EC9706 cells. The mRNA and protein expression of Notch1 gene in pcNICD-transfected EC9706 cells were significantly increased by about 3 folds of those in untreated and pcDNA3.1-transfected cells (P<0.01). However, there was no difference in Notch1 expression between untreated and pcDNA3.1-transfected EC9706 cells (P>0.05). The apoptosis rate was significantly higher in pcNICD-transfected EC9706 cells than in untreated and pcDNA3.1-transfected cells (P<0.01); there was no prominent difference between untreated and pcDNA3.1-transfected EC9706 cells (P>0.05). CONCLUSION: The activated Notch1 signaling pathway gives rise to the apoptosis of EC9706 cells, suggesting that Notch1 gene may be a new therapeutic target for ESCC.

[Transformation of Dunaliella salina by using glass beads--a novel transformation method].

A novel transformation method was firstly established using glass beads in Dunaliella salina (D. salina). The results showed that the GUS gene, a reporter gene, was successfully expressed in D. salina. Cells of D. salina presented blue color under the microscope after stained. In addition, different factors which influenced transformation were optimized including the transformation consecutive time, rotate speed, concentration of the plasmid and PEG 6000. The experiment indicated that this fit together can obtain the best results for D. salina transformation: adding 150 microL PEG and 90 microL plasmid DNA to 800 microL culture of D. salina (10(6) cells/mL) containing 300 mg glass beads, swirling 12 seconds under the rotate speed 2400r/min. This newly method can be used as a potential tool in the research of D. salina gene engineering with the advantage of more simpleness, convenience, quickness and less expense.

Nuclear factor-kB signaling pathway constitutively activated in esophageal squamous cell carcinoma cell lines and inhibition of growth of cells by small interfering RNA.

Although constitutive nuclear factor (NF)-kappaB activation has been reported in many human tumors, the role of the NF-kappaB pathway in esophageal squamous cell carcinoma (ESCC) has not been known. In this study, NF-kappaB pathway in two ESCC cell lines was investigated using immunocytochemistry, Western blot and reverse transcription-polymerase chain reaction. The activation of NF-kappaB DNA binding was determined by electrophoretic mobility-shift assay. RNA interference was used to specifically inhibit the expression of p65. Growth of cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The results showed that p50, p65, IkappaBalpha p-IkappaBalpha and IkappaB kinase beta were expressed and mainly localized in the cytoplasm. Reverse transcription-polymerase chain reaction results showed the constitutive expressions of p50, p65 and IkappaBalpha mRNA in the two ESCC cell lines. Furthermore, the nuclear extracts revealed that p50 and p65 translocated to the nucleus had DNA-binding activity. Finally, small interfering RNA of p65 decreased the expression of p65, and the viability of cells transfected with p65 small interfering RNA was significantly suppressed at the same concentration of 5-fluorouracil (P < 0.05) compared to untransfected cells. The results of this study showed that there was the constitutively activated NF-kB signaling pathway in the ESCC cell lines. RNA interference targeting at p65 increased the sensitivity of the ESCC cell lines to 5-fluorouracil, suggesting that NF-kappaB might be a good target for cancer treatment.

Expression of recombinant kringle 1-5 domains of human plasminogen by a prokaryote expression system.

Kringle1-5 (K1-5), a proteolytic fragment containing five kringle domains of human plasminogen generated by plasmin-mediated proteolysis, has been already identified by Cao et al. with relation to anti-angiogenesis and proliferation of endothelial cells. To investigate anti-angiogenesis activity of recombinant human K1-5 (rhK1-5) expressed in Escherichia coli BL21, the cDNA of human K1-5 obtained from cloning vector pUC57-K1-5 by PCR, was inserted into an expression vector pET30(+) to construct a prokaryotic expression vector pET-K1-5. Recombinant K1-5 efficiently expressed in E. coli BL21 after IPTG induction was monitored by SDS-PAGE and Western blotting with an anti-angiostatin monoclonal antibody and an anti-hexahistidine tag antibody. The expressed K1-5 accounted for approximately 32% of the total bacterial proteins as estimated by densitometry, and existed mainly as inclusion bodies. The inclusion bodies were washed, lysed, purified, and refolded to a purity of 96% as estimated by capillary electrophoresis and the final purification yield of K1-5 in E. coli system was approximately 5.8 mg/L. Purified K1-5 protein was tested on chicken embryo chorioallantoic membranes (CAMs), and a large number of newly formed blood vessels were significantly regressed. In the present study, we demonstrated that bacterial-expressed K1-5 effectively inhibited angiogenesis of the chicken embryo in a dose-dependent manner through CAM assay. In addition, the rhK1-5 potently inhibited endothelial cell proliferation but not non-endothelial cells. For the first time, these findings demonstrate that the rhK1-5 produced by a prokaryote expression system effectively inhibited angiogenesis of the chicken embryo in a dose-dependent manner and specially suppressed in vitro the proliferation of human umbilical vein endothelial cells. This fact derived from the present study further suggests the rhK1-5 can be used for anti-angiogenesis therapy of cancer.

[Cloning and analysis of psaB cDNA of Dunaliella salina].

One pair of degenerate primer was designed according to conserved motifs of the psaB (A2 subunit of photosystem I) of Chlamydomonas reinhardtii, Chlamydomonas moewusii, Chlorella vulgaris and Mesostigma viride, and a total RNA of Dunaliella salina (D. salina) was extracted with TRIzol reagent. A cDNA fragment, about 1.8kb in length, from green algal D. salina was obtained through RT-PCR method. The resulting PCR product was cloned into T-vector and screened to determine its sequence. Homologous analysis of the deduced amino acid sequence was performed by BLAST and subsequeqtly compared with GenBank data. The obtained cDNA sequence was 1815 bp long, which encodes 605 amino acids (GenBank accession number: AY820754). The sequence shared high homologue with the following psaB: Chlamydomonas reinhardtii 92%, Chlamydomonas moewusii 91%, Chlorella vulgaris 86%, Mesostigma viride 85%, Physcomitrella patens subsp. Patens 85% and Nephroselmis olivacea 84%. It can be concluded that the cloned sequence is psaB cDNA fragment from D. salina.

[Preparation of human recombinant kringle 1-5 and its bioactivity].

To investigate antiangiogenesis activity and effects on endothelial cell proliferation of human recombinant K1-5 expressed in E.coli BL21, the cDNA of human K1-5 obtained from a cloning vector pUC57K1-5 by PCR, was inserted into an expression vector pET30(+) to construct a prokaryotic expression vector pET-K1-5. Recombinant K1-5 efficiently expressed in E.coli BL21 after IPTG induction was monitored by SDS-PAGE and Western blotting with an anti-angiostatin monoclonal antibody. The expressed K1-5 accounted for approximately 32% of the total bacterial proteins as estimated by densitometry, and existed mainly as inclusion bodies. The inclusion bodies were washed, lysed and purified to a purity of 96% by the nickel affinity chromatography. Refoled K1-5 protein was tested on chicken CAMs, and a large number of newly formed blood vessels were significantly regressed. In the present study, we demonstrated that bacterial-expressed K1-5 effectively inhibited angiogenesis of the chicken embryo in a dose-dependent manner through CAM assay. In addition, human recombinant K1-5 potently inhibited endothelial cell proliferation with no inhibition on non-endothelial cells. Taken together, these findings demonstrated that human recombinant K1-5 effectively inhibited angiogenesis of the chicken embryo in a dose-dependent manner and specially suppressed in vitro the proliferation of human umbilical vein endothelial cells.

The actin gene promoter-driven bar as a dominant selectable marker for nuclear transformation of Dunaliella salina.

A 5'-flanking region of an actin gene from the green unicellular alga Dunaliella salina (D. salina) was cloned using a genome-walking method by PCR and its structural features were characterized. Two repetitive sequences found, over 75 bp in length each, were located at position -573 and -424 bp,respectively, relative to the AUG codon. The actin gene promoter region of D. salina displayed a consensus sequence of GCTC (G/C) AAGGC, a CCAAT motif and two TATA-like motifs that did not have a canonical sequence of a TATA box. The 5' flanking region of the actin gene was exploited to direct expression of the bialaphos resistance gene (bar) from Streptomyces hygroscopicus as a dominant marker in the nuclear transformation of D. salina. Direct selection of bar resistant transformants was achieved by allowing a 24 h period of recovery of cells transformed by biolistic procedure, followed by growth of the cells for one week under standard condition prior to harvesting and plating on the solid medium containing 0.5 microg/mL of phosphinothricin (PPT). Five colonies picked from the plate were analyzed, of which the integration of the bar gene was demonstrated in the nuclear genome. Southern blotting revealed that only one of five transformants contained a single copy of the bar gene whereas others contained multiple copies,suggesting that nuclear transformation of D. salina mainly occurred through illegitimate recombination events,resulting in ectopic integration of the introduced DNA. The integration patterns of the foreign DNA in this experiment appeared not to influence the bar gene expression in the transformants containing single or multiple inserts. The bar gene expression in the five transformants was verified by RT-PCR, confirming transcription of the chimeric DNA. These transformants were maintained on agar plates in the absence of PPT for more than seven months and retained resistance to the herbicide at 1 microg/mL. This work demonstrates that the actin gene promoter-driven expression of the bar gene may be used as a dominant selectable marker for nuclear transformation of D. salina.

[Construction of randomly matrix attachment regions library from the green alga: Dunaliella salina].

Matrix attachment region (MAR) is DNA fragment that can bind to the nuclear matrix. In order to isolate the MAR fragment from the halotolerant green alga Dunaliella salina, we created a library of randomly obtained MAR from D. salina. Firstly the intact nuclei were released using 0.5% Triton X-100, then purification was carried out by discontinuous centrifugation using 30% and 70% Percoll gradients. Histones of nuclear matrices were removed using 25mmol/L lithium dioodosalicylate, the DNAs not closely associated with the matrices were removed using restriction enzymes. The remained matrices DNAs were digested by proteinase K, extracted with phenol/chloroform and precipitated with ethanol, and then cut with four kinds of restriction enzymes, the resulting DNAs were subsequently ligated to pUC18-vector and transferred to E. coli JM109 strains, DNA sequencing showed that the DNA fragments had the features of MAR DNA fragments.

Nuclear matrices and matrix attachment regions from Green alga: Dunaliella salina.

Nuclear DNA of eukaryotic organism attaches to the proteinaceous nuclear matrices via specific matrix attachment regions (MARs). In order to investigate the interactions between chromosomal DNA and nuclear matrices,we isolated the MARs from unicellular alga Dunaliella salina. As the first step,a random MAR library was set up and then the binding affinity of the selected clones to nuclear matrices was tested in this study. Three DNA fragments were found to bind specifically to the nuclear matrices in vitro,of which two were strong binders and all contained known consensus motifs and a hairpin loop structure of MAR.

Recombinant mouse canstatin inhibits chicken embryo chorioallantoic membrane angiogenesis and endothelial cell proliferation.

Human canstatin, a 24 kD fragment of the alpha2 chain of type IV collagen, has been proved to be one of the most effective inhibitors of angiogenesis and tumor growth. To investigate in vivo antiangiogenesis activity and in vitro effects on endothelial cell proliferation of recombinant mouse canstatin, the cDNA of mouse canstatin was introduced into an expression vector pQE40 to construct a prokaryotic expression vector pQE-mCan. The recombinant mouse canstatin efficiently expressed in E. coli M15 after IPTG induction was monitored by SDS-PAGE and by Western blotting with an anti-hexahistidine tag antibody. The expressed mouse canstatin, mainly as inclusion bodies, accounted for approximately 35% of the total bacterial proteins. The inclusion bodies were washed, lysed and purified by the nickel affinity chromatography to a purity of approximately 93%. The refolded mouse canstatin was tested on the chicken embryo chorioallantoic membranes (CAM), and a large number of newly formed blood vessels were significantly regressed. In addition, recombinant mouse canstatin potently inhibited endothelial cell proliferation with no inhibition on non-endothelial cells. Taken together, these findings demonstrate that the recombinant mouse canstatin effectively inhibited angiogenesis of the chicken embryo in a dose-dependent manner and specially suppressed in vitro the proliferation of human umbilical vein endothelial cells.

[Cloning and functional analyses of promoters of two carbonic anhydrase genes from Dunaliella salina].

The cloning vectors pMD-DCA1 and pMD-CA containing the promoters of duplicated carbonic anhydrase 1 (DCA1) and carbonic anhydrase (CA) genes, respectively, from Dunaliella salina, and expression vector pDM307 containing bar-NOS polyA fragment were digested with EcoR I. The bar-NOS polyA fragment was fused, respectively, to the fragments of the vectors pMD-DCA1 and pMD-CA to form transgenic D. salina expression vectors pMDDC-B and pMDC-B. The micro-shots were prepared by coating two constructs (pMDDC-B and pMDC-B) with gold particle. Each sample was bombarded once, twice, and thrice, respectively, with micro-projectile gun at a rupture pressure of 690 kPa in helium gas. The screening culture of the bombarded alga cells was performed in PKS liquid and solid medium containing 3 mg/L phosphinothricin (PPT) to develop the transformed cells of D. salina. Analyses of the transformed cells were carried out through PCR, Southern blotting, and Northern blotting. The results of screening culture showed that the expression of the external bar gene of vectors pMDDC-B and pMDC-B was stable and transient, respectively, in the transformed D. salina cells. In the meantime, the transformed efficiency of particle bombardment twice was higher than that of once or thrice particle bombardment at a rupture pressure of 690 kPa in helium gas. PCR and Southern blotting analyses indicated that the external bar gene was integrated into the genome of the cells. Northern analysis indicated that expression efficiency of the bar gene driven by DCA1 promoter was regulated by the gradient concentration of sodium chloride, and the positive blotting signal intensity of the bar mRNA was highest in the medium containing 2 mol/L of sodium chloride. The findings of the present study suggest that promoter of the DCA1 gene may be an inducible promoter following a hyperosmotic shock with high activity and safety in the research of transgenic D. salina. The tandem GT sequences of the promoter region of DCA1 and CA genes may be related to the molecular mechanisms of the extreme halo-toleration of the unicellular green alga, D. salina.

[Expression of mouse canstatin and its N-domain in E. coli BL21].

The mouse canstatin and its N-domain cDNA were amplified from total RNA of mouse liver by RT- PCR and cloned into vector pMD18-T for sequencing. Prokaryotic expression vectors pET/Can and pET/Can-N were constructed and expressed in E.coli BL21(DE3) with induction of IPTG.. Mouse canstatin cDNA is 684bp in length encoding 227 amino acids. The sequences of both cDNA and amino acids share high homology with human canstatin, with cDNA identity at 89% and amino acids identity at 96% to human canstatin. N-domain of mouse canstatin is the same amino acid sequence as that of human canstatin. In the present study, prokaryotic expression vector pET/Can and pET/Can-N were expressed in E.coli BL21 with amount of 35% and 18% of the total bacterial proteins after being induced by IPTG for 4h. The expressed products existed mainly as inclusion bodies. This work has laid down the basis for further study of its angiogenic activity and potential application for tumor dormancy therapy.

[Cloning and characterization of Hsp70a cDNA fragment of Dunaliella salina].

The present study is to obtain heat shock protein 70a cDNA fragment from Dunaliella salina. Two pairs of degenerate primers were designed according to conserved motifs of DIDLGTT,DQGNRTTP,PAYFNDS and ATKDAG of the homologous amino acid sequences and used to amplify hsp70a cDNA fragment from heat-shock-treated Dunaliella salina by nest PCR technique. The resulting PCR products were inserted into T-vector then transformed into JM109. Ten colonies were selected to determine their sequences. Homologous analysis of the deduced amino acid sequences were performed by BLAST and subsequently compared with GenBank data. Three of ten nucleotide sequences were obtained,of which there was 372 bp coding 126 amino acids. The sequences shared high homology with hsp70a,with identity 96% to Chlamydomonas reinhardtii, 94% to Petunia, 93% to Pisumsativum, 92% to tomato, 92% to human,90% to Drosophila and 89% to yeast respectively. It can be concluded that the cloned sequence is putatively hsp70a cDNA fragment from Dunaliella salina.