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.

Inhibitory effect of human telomerase antisense oligodeoxyribonucleotides on the growth of gastric cancer cell lines in variant tumor pathological subtype

AIM: To investigate the inhibitory effect of specialized human telomerase antisense oligodeoxyribonucleotides on the growth of well (MKN-28), moderately (SGC-7901)and poorly (MKN-45) differentiated gastric cancer cell lines under specific conditions and its inhibition mechanism,and to observe the correlation between the growth inhibition ratio and the tumor pathologic subtype of gastric cancer cells.METHODS: Telomerase activity in three gastric cancer cell lines of variant tumor pathologic subtype was determined by modified TRAP assay before and after the specialized human telomerase antisense oligodeoxyribonucleotides were dealt with under specific conditions. Effect of antisense oligomer under specific conditions of the growth and viability of gastric cancer cell lines was explored by using trypan blue dye exclusion assay, and cell apoptosis was detected by cell morphology observation, flow cytometry and TUNEL assay.RESULTS: Telomerase activity was detected in well,moderately and poorly differentiated gastric cancer cell lines (the quantification expression of telomerase activity was 43.7TPG, 56.5TPG, 76.7TPG, respectively).Telomerase activity was controlled to 30.2TPG, 36.3TPG and 35.2TPG for MKN-28, SGC-7901 and MKN-45 cell lines respectively after treatment with human telomerase antisense oligomers at the concentration of 5 μmol/L, and was entirely inhibited at 10 μmol/L, against the template region of telomerase RNA component, whereas no inhibition effect was detected in missense oligomers (P＜0.05). After treatment with antisense oligomers at different concentrations under specific conditions for 96 h, significant growth inhibition effects were found in MKN-45 and SGC-7901gastric cancer cell lines (the inhibition ratio was 40.89%and 71.28%), but not in MKN-28 cell lines (15.86%). The ratio of inactive SGC-7901 cells increased according to the prolongation of treatment from 48 to 96 h. Missense oligomers could not lead to the same effect (P＜0.05).Apoptosis of SGC-7901 and MKN-45 cells was detected not only by morphology and TUNEL assay but also by flow cytometry. The apoptotic rate reached 33.56% for SGC-7901 cells and 44.75% for MKN-45 cells.CONCLUSION: The viability and proliferation of gastric cancer cells can be inhibited by antisense telomerase oligomers. The growth inhibition of gastric cancer cells is correlated with concentration, time and sequence specialty of antisense oligomers. The inhibition mechanism of antisense human telomerase oligomers depends not only on the sequence specialty but also on the biological characteristics of gastric cancer cell lines.