Suicide gene therapy using keratin 19 enhancer and promoter in malignant mesothelioma cells.

To achieve the specific expression of a transfected suicide gene in malignant mesothelioma cells, we applied the enhancer-promoter fusion sequence of the keratin 19 (K19) gene. Northern blot analysis of three mesothelioma cell lines demonstrated that K19 mRNA was expressed most abundantly in the H2052 mesothelioma cell line. Subsequently, in a luciferase reporting assay, K19 promoter (260 bp) exhibited higher promoter activity in H2052 cells than in the other two cell lines. In addition, ligation of a 3' enhancer (80 bp) of the K19 gene to upstream of the K19 promoter sufficiently enhanced the promoter activity. After transfecting an expression vector containing the K19 enhancer-promoter bound thymidine kinase gene (pK19-TK) into the H2052 cells, the pK19-TK transfected cells became more sensitive to GCV than non-transfected cells in vitro and in vivo. In a mouse peritoneal model of malignant mesothelioma, in vivo transfection of pK19-TK by cationic liposome and systemic administration of GCV inhibited the growth of peritoneal tumors. The K19 enhancer-promoter sequence seemed to be specific and efficient enough for the expression of the transfected suicide gene in malignant mesothelioma cells.