Effective combination gene therapy using CEACAM6-shRNA and the fusion suicide gene yCDglyTK for pancreatic carcinoma in vitro

The incidence of pancreatic carcinoma, a gastrointestinal malignancy, is on the increase and effective therapeutic strategies are therefore required. This study aimed to construct a recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK from CEACAM6 targeting shRNA and the fusion suicide gene yCDglyTK for inhibition of SW1990 human pancreatic carcinoma cell growth and invasion. A plasmid containing hU6 promoter and CEACAM6 targeting short hairpin RNA (CEACAM6-shRNA) frame was constructed. It was subcloned to a CEA promoter-driven fusion suicide gene pcDNA3.1(-)yCDglyTK. The recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK was identified by restriction endonuclease analysis and DNA sequencing. The recombinant plasmid was delivered into SW1990 human pancreatic carcinoma cells, the mRNA and protein expression of yCDglyTK and CEACAM6 was examined by RT-PCR, western blot analysis and immunofluorescence. SW1990 cells were treated with the prodrug 5-fluorocytosine (5-FC), and the cell viability was evaluated using the 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The invasiveness and migration of SW1990 cells were evaluated by transwell migration assays. The restriction endonuclease analysis and DNA sequencing confirmed the construction of the recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK. Reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis outcomes showed that yCDglyTK was expressed in SW1990 cells and expression of CEACAM6 in SW1990 cells was significantly knocked down. MTT assay showed that the mean viability of SW1990 cells was significantly reduced after administration of the prodrug 5-FC in vitro. Transwell migration assays showed that invasion and migration action of SW1990 cells was significantly inhibited. In conclusion, recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK was successfully constructed. The recombinant plasmid may therefore serve as a novel gene therapy approach for pancreatic carcinoma.