ABSTRACT
Objective To investigate the cytotoxic effects and mechanism of PNP-CD chimeric gene vector originated from PNP/MeP-dR system on HCC cells. Methods The fusion suicide gene PNP-CD obtained by site directed mutagenesis technique was subcloned into pcDNA3.0 to construct a eukaryotic expression vector containing a chimeric gene, pcDNA3.0/ PNP-CD. After being identified by recombinant enzyme, PCR and subsequent sequencing, it was transfected into HepG2 cells by liposome-mediation method. The G418-resistant cellular clone with stable transfection of pcDNA3.0/PNP-CD, HepG2/PNP-CD was established by selection. The expression of PNP-CD gene was also verified by RT-PCR and Western blotting. The curve of cellular growth was assayed by Trypan blue exclusion. The cellular sensitivity of HepG2/PNP-CD to its specific prodrugs and its bystander effects were also assayed by MTT method. Results The chimeric gene, PNP-CD, was inserted into pcDNA3.0 correctly, and the stable expression of pcDNA3.0/PNP-CD in HepG2 cells was confirmed.This cellular clone was highly sensitive to its corresponding prodrugs. It was indicated that its bystander effects with the synergetic treatment of its specific prodrugs were substantially higher than those caused by the same vector with the administration of only a single prodrug, MeP-dR. Conclusion The bi-functional fusion suicide gene vector, pcDNA3.0/PNP-CD, yields powerful cytotoxic effects on HCC cells in the presence of the synergetic treatment of its specific prodrugs, which would be a high-performance therapeutic vector in gene therapy for liver cancer.
ABSTRACT
To investigate the killing effect of PNP/MeP-dR suicide gene system on hepatoma cells,pcDNA3. 0/PNP, an eukaryotic expression vector harboring E. coli PNP gene, was transfected into human hepatoma HepG2 cells by liposome-mediated method. A HepG2 cell line with stable PNP gene expression, HepG2/PNP, was established with presence of G418 selection. The cell growth curves were determined with trypan blue staining. The sensitivity of HepG2/PNP to MePdR and bystander effects were assayed by MTT and FCM methods. The enzymatic activity of the product of PNP gene was determined by HPLC method. The cytotoxic effects of MeP-dR on HepG2/PNP cells were obvious (IC50 =4.5μmol/L) and all HepG2/PNP cells were killed 4 days after the treatment with 100μmol/L MeP～dR. In mixed cultures containing increasing percentages of HepG2/PNP cells, total population killing was demonstrated when HepG2/PNP cells accounted for as few as 5% of all HepG2 cells 8 days after the treatment with 100μmol MeP-dR. Highpressure liquid chromatography (HPLC) demonstrated that the PNP enzyme could convert MePdR into 6-MP. PNP/MeP-dR suicide gene system had an advantage over traditional suicide gene systems for hepatoma gene therapy. Our e results suggest that high-level bystander effects of this system result in significant anti-tumor responses to hepatoma gene therapy, especially in vivo.
ABSTRACT
Objective To construct an expression vector harboring CYP2B1 suicide gene, and detect its expressions in tumor cell lines. Methods PCR amplification was performed using primers based on murine CYP2B1 gene sequence from gene bank and pc3/2B1 as template. PCR product was directly inserted an eukaryotic expression plasmid pcDNA3.0. The recombinants were analyzed and identified by restriction enzyme analysis, PCR and sequencing. Then the recombinant vector pcDNA3.0/CYP2B1 was transfected into three tumor cell lines by liposome-mediated method. The expressions of CYP2B1 gene in all the cell lines were detected by RT-PCR method. Results pCDNA3.0/CYP2B1 vector was successfully constructed, and could express CYP2B1 mRNA in the three tumor cell lines. Conclusion Eukaryotic expression vector pcDNA3.0/CYP2B1 containing CYP2B1 gene under the control of a CMV promoter is an novel effective expression vector for tumor gene therapy.