Long-term and stable expression of transgene mediated by piggyBac transposon in gynecological malignant tumor cells

Abstract

To investigate the expression of exogenous gene transferred by piggyBac (PB) transposon in various gynecological malignant cell lines and reveal its potential application of gene therapy in gynecological cancer. Amplified herpes simplex virus thymidine kinase (HSV-tk) gene coding region by PCR and integrated it into PB expression vector, PB[Act-RFP]DS, for reconstructing PB[Act-RFP, HSV-tk]DS (pPB/TK). By using different transfection reagents: FuGENE HD, jetPEI, lipofectamine 2000, pPB/TK together with helper plasmid Act-PBase were cotransfected into four mostly common gynecological malignant tumor cell lines HeLa, JEG-3, SKOV3 and HEC-1B. The mRFP1 report gene expressions was observed and detected by fluorescence microscope and flow cytometry to analyze transfection efficiency. The expressions of HSV-tk and mRFP1 gene were detected by reverse transcription PCR (RT-PCR). The cytotoxic effect of various concentration of pro-drug ganciclovir (GCV) for transfected cells was detected by methyl thiazole tetrazolium assay. The transfected cells were positive sorted by flow cytometry and limiting diluted to obtain the stable transfected cell line. The insertion sites of foreign gene transferred by PB transposon in genome were analyzed by inverse PCR. (1) Double digests analysis and sequences test demonstrated that pPB/TK vector was reconstructed successfully. (2) Using three different transfective reagents, PB transposon transferred HSV-tk gene and mRFP1 gene into HeLa, HEC-1B, SKOV3 and JEG-3 cell efficiently, and the transfection efficiency of pPB/TK for the same cell was different by using different transfective reagents; in Hela cell, the transfection efficiency of FuGENE HD [(78.7+/-9.2)%] was higher than that of lipofectamine 2000 [(54.1+/-11.4)%] and jetPEI [(46.5+/-7.4)%, all P<0.05]; using the same transfective reagent, the transfection efficiency of pPB/TK was also different on various cell lines, using FuGENE HD, the transfection efficiency of pPB/TK on HeLa, JEG-3 and SKOV3 cell was (78.7+/-9.2)%, (74.4+/-8.9)% and (83.2+/-9.7)% respectively, which all were higher than that on HEC-1B [(39.5+/-8.7)%, P<0.05]. (3) RT-PCR showed that there were the mRNA expression of HSV-tk and mRFP1 in all cell lines. (4) 50% inhibitory concentration of GCV for transfected cells, HeLa, JEG-3, SKOV3 and HEC-1B, was 1.29, 3.35, 0.09 and 13.28 microg/ml respectively. Inhibitory effect of GCV (10 microg/ml) on SKOV3 transfected with pPB/TK was (86+/-9)%, which was superior to that transfected with pORF-HSVtk alone [(52+/-12)%, P<0.05]. (5) The insertion sites of PB transposon in the target cells genome were located at TTAA sites. mRFP1 expression still could be detected in three months after transfected. PB transposon could transfer exogenous gene into various gynecological malignant cells, which could integrated into genome and obtain a long-term and stable expression. It is expected that PB transposon may supply a more efficient and safer transgene technology platform for gene therapy in gynecological cancer.