Gene therapy for human colorectal carcinoma using human CEA promoter controlled bacterial ADP-ribosylating toxin genes: PEA and DTA gene transfer

AIM To establish a tissue-specific gene therapy for colorectal carcinoma using bacterial ADP-ribosylating toxin genes. METHODS Pseudomonas exotoxin A domain II + ill (PEA) was cloned from genomic DNA of Pseudomonas aeruginosa. PEA and diphtheria toxin A chain gene (DTA) were modified to express eukaryotically. After sequencing, the toxin genes under the control of human carcinoembryonic antigen (CEA) promoter were cloned into retroviral vectors to construct CEAPEA and CEADTA respectively. In vitro cotransfection of the constructs with luciferase vectors and in vivo gene transfer in nude mice were subsequently carried out. RESULTS Both CEAPEA and CEADTA specifically inhibited the reporter gene expression in the CEA positive human colorectal carcinoma (CRC) cells in vitro. Direct injection of CEAPEA and CEADTA constructs into the established human tumors in BALB/c nude mice led to significant and selective reductions in CRC tumor size as compared with that in control groups. CONCLUSION The toxin genes, working as therapeutic genes, are suitable for the tissue-specific gene therapy for colorectal carcinoma.