Insertion of nuclear factor-kB binding sequence into plasmid DNA for increased transgene expression in colon carcinoma cells

To increase plasmid DNA (pDNA)-based transgene expression, 5, 10 or 20 repeats of nuclear factor kB (NF-kB) binding sequences were inserted upstream of the cytomegalovirus (CMV) promoter region of a conventional pDNA encoding firefly luciferase (pCMV-Luc) to obtain PCMV-kB5-Luc, PCMV-kB10-Luc and PCMV-kB20-Luc. Murine carcinoma colon 26 cells, in which NF-kB was constitutively activated, were co-transfected with a firefly luciferase-expressing pDNA and a renilla luciferase-expressing pDNA having no NF-kB binding sequences using cationic liposomes. The expression efficiency of pCMV-kB(n)-Luc was evaluated using the ratio of the luciferase activities. Increasing numbers of NF-kB binding sequences significantly increased transgene expression. The expression was increased by NF-kB activators and the effects were marked with pDNA having many NF-kB binding sequences. These results indicate that insertion of NF-kB binding sequences into pDNA is an effective approach to increase transgene expression in cancer cells in which NF-kB is activated. (C) 2007 Elsevier B.V. All rights reserved.