Knockdown of survivin gene expression by RNAi induces apoptosis in human hepatocellular carcinoma cell line SMMC-7721

AIM: To investigate the survivin gene expression in human hepatocellular carcinoma cell line SMMC-7721 and the effects of survivin gene RNA interference (RNAi) on cell apoptosis and biological behaviors of SMMC-7721 cells.METHODS: Eukaryotic expression vector of survivin gene RNAi and recombinant plasmid pSuppressorNeo-survivin (pSuNeo-SW), were constructed by ligating into the vector,pSupperssorNeo (pSuNeo) digested with restriction enzymes Xba I and Sa/I and the designed double-chain RNAi primers. A cell model of SMMC-7721 after treatment with RNAi was prepared by transfecting SMMC-7721 cells with the lipofectin transfection method. Strept-avidinbiotin-complex (SABC) immunohistochemical staining and RT-PCR were used to detect survivin gene expressions in SMMC-7721 cells. Flow cytometry was used for the cell cycle analysis. Transmission electron microscopy was performed to determine whether RNAi induced cell apoptosis, and the method of measuring the cell growth curve was utilized to study the growth of SMMC-7721 cells before and after treatment with RNAi.RESULTS: The eukaryotic expression vector of survivin gene RNAi and pSuNeo-SW, were constructed successfully. The expression level of survivin gene in SMMC-7721 cells was observed. After the treatment of RNAi, the expression of survivin gene in SMMC-7721 cells was almost absent,apoptosis index was increased by 15.6%, and the number of cells was decreased in G2/M phase and the cell growth was inhibited.CONCLUSION: RNAi can exert a knockdown of survivin gene expression in SMMC-7721 cells, and induce apoptosis and inhibit the growth of carcinoma cells.

Construction of a regulable gene therapy vector targeting for hepatocellular carcinoma

AIM: To construct a gene modified hepatocellular carcinoma (HCC) specific EGFP expression vector regulated by abbreviated cis-acting element of AFP gene.METHODS: The minimal essential DNA segments of AFP gene enhancer and promoter were synthesized through PCR from Genome DNA of HepG2 cells. Gene fragments were then cloned into the multiple cloning site of non-promoter EGFP vector pEGFP-t. Recombinant plasmid was transferred into positive or negative AFP cell lines by means of lipofectamine. The expression of EGFP was tested by fluorescence microscope and flow cytometry. The effect of all-trans retinoic acid (ATRA) on the expression of EGFP was tested in different concentrations.RESULTS: By the methods of restriction digestion and sequence analyses we confirmed that the length, position and orientation of inserted genes of cis-acting element of AFP were all correct. The transcription of EGFP was under the control of AFP cis-acting element. The expressing EGFP can only been detected in AFP producing hepatoma cells.The expression rate of EGFP in G418 screened cell line was 34.9±4.1%. 48 h after adding 1×10-7M retinoic acid, EGFP expression rate was 14.7±3.5%. The activity of AFP gene promoter was significantly suppressed by addition of 1×10-7M retinoic acid (P＜0.05, P=0.003, t=6.488).CONCLUSION: This recombinant expression vector can be used as a gene therapy vector for HCC. The expression of tumor killing gene will be confined within the site of tumor and the activity of which can be regulated by retinoic acid.

Localization of TRAIL/TRAILR in fetal pancreas

AIM: To observe the localization of TRAIL/TRAIR (DR4, DR5,DcR1, DcR2) in the fetal pancreas.METHODS: Fetal pancreas of 32 weeks of pregnancy wereobtained from induced abortions, embedded in paraffin, and4-μm sections were prepared. The localization of TRAIL/TRAILR in fetal pancreas was investigated by fluorescenceimmunohistochemical method combined with laser scanningconfocal microscopy.RESULTS: TRAIL immunoreactive cells were mainly locatedon the periphery of the pancreas islets. There were a fewDcR1 and DcR2 positive cells whereas there were noimmunoreactive cells of DR4 and DR5 in the pancreas islets.In the acini and the ducts of the exocrine pancreas therewere no TRAIL/TRAILR immunoreactive cells.CONCLUSION: This study not only describes thedistribution of TRAIL/TRAILR in the fetal pancreas, but alsoprovides a morphological basis for deducing the functionof TRAIL/TRAILR in pancreas, suggesting that in normalpancreatic islets, the pancreatic cells are resistant towardsapoptosis too.