For specific transduction of herpes simplex virus thymidine kinase (HSV-tk) into human small-cell lung carcinoma (SCLC) cells, we explored the 5'-flanking region (-1.1 kb) of the gastrin-releasing peptide (GRP) gene as a lung cancer-specific promoter. RT-PCR analysis demonstrated expression of GRP mRNA in the SBC5 human SCLC cell line but not in the RERF human SCLC cell line, the A549 human lung adenocarcinoma cell line or the HeLa human uterine cervix epithelioid carcinoma cell line. A reporting vector containing the GRP promoter (pGL2-GRP) exhibited higher luciferase activity in SBC5 than in the other 3 cell lines. After transfecting an expression vector containing the GRP promoter-bound HSV-tk gene (pGRP-TK) into the cells, we measured their sensitivity to ganciclovir (GCV). In SBC5, pGRP-tk-transfected cells became about 100 times more sensitive to GCV than parental cells in vitro. In nude mice, tumors of pGRP-tk-transfected SBC5 regressed completely after i.p. administration of GCV. GRP promoter might be a good tool for tumor-specific transduction of suicide genes in GRP-expressing SCLC cells.
Copyright 2000 Wiley-Liss, Inc.