Cell growth- and P53-dependent transcriptional activity of the midkine promoter confers suicide gene expression in tumor cells.
Midkine (MK) is preferentially expressed in a number of human tumors, while the expression in adult normal tissues is restricted. Previous studies showed that a 2.3-kb regulatory region of the human MK gene could selectively activate a linked suicide gene in tumors. In this study, we explored the minimal promoter region using genomic fragments deleted from the 5'-upstream side and analyzed the mechanism of the preferential activation in tumor cells. Luciferase assays showed that the 0.3-kb fragment from the transcription start site contained a cis-acting element(s) for the promoter activity. Expression of the herpes simplex virus-thymidine kinase gene under the control of the MK promoter followed by ganciclovir administration produced antitumor effects in vivo. Transfection of the wild-type p53 gene into the immortalized fibroblasts bearing mutated p53 and tumor cell lines, which induced cell cycle arrest, decreased the MK promoter-mediated transcription more effectively than the SV40 or the cytomegalovirus promoter-mediated transcription. The P53-mediated downregulation of the MK promoter activity was stronger in p53-defective tumors than in wild-type p53-bearing tumors. Moreover, the MK promoter-mediated luciferase activity was greater in p53-deficient mouse embryonic fibroblasts than in those bearing wild-type p53 gene. The transcriptional activity of the MK promoter could be regulated by cell growth and in part P53-dependent pathways.
Yu
Ling
L
Division of Pathology, Chiba Cancer Center Research Institute, Chiba, Japan.
Ugai
Shin-Ichi
S
O-Wang
Jiyang
J
Namba
Masayoshi
M
Kadomatsu
Kenji
K
Muramatsu
Takashi
T
Matsubara
Shuichiro
S
Sakiyama
Shigeru
S
Tagawa
Masatoshi
M
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D016923:Cell Death; D002455:Cell Division; D016207:Cytokines; D003587:Cytomegalovirus / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D016158:Genes, p53; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D000078792:Midkine; D009154:Mutation; D009369:Neoplasms / Q000235:genetics; D011401:Promoter Regions, Genetic; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection
D002352:Carrier Proteins; D016207:Cytokines; D000078792:Midkine; D008156:Luciferases; D013937:Thymidine Kinase