Complete regression of human malignant mesothelioma xenografts following local injection of midkine promoter-driven oncolytic adenovirus.
BACKGROUND
Malignant mesothelioma is a highly aggressive tumor with poor prognosis. We hypothesized that the tumor-specific midkine (Mdk) promoter could confer transcriptional targeting to oncolytic adenoviruses for effective treatment of malignant mesothelioma.


METHODS
We analysed Mdk expression by quantitative reverse transcription-polymerase chain reaction in six human mesothelioma cell lines, and tested Mdk promoter activity by luciferase reporter assay. On the basis of these data, we constructed a replication-selective oncolytic adenovirus designated AdMdk-E1-iresTK. This virus contains a Mdk promoter-driven adenoviral E1 gene and herpes simplex virus-thymidine kinase (TK) suicide gene and cytomagalovirus promoter-driven enhanced green fluorescent protein marker gene. Selectivity of viral replication and cytolysis were characterized in normal versus mesothelioma cells in vitro, and intratumoral spread and antitumor efficacy were investigated in vivo.


RESULTS
Mdk promoter activity was restricted in normal cells, but highly activated in mesothelioma cell lines. AdMdk-E1-iresTK was seen to efficiently replicate, produce viral progeny and spread in multiple mesothelioma cell lines. Lytic spread of AdMdk-E1-iresTK mediated the efficient killing of these mesothelioma cells, and its in vitro cytocidal effect was significantly enhanced by treatment with the prodrug, ganciclovir. Intratumoral injection of AdMdk-E1-iresTK caused complete regression of MESO4 and MSTO human mesothelioma xenografts in athymic mice. In vivo fluorescence imaging demonstrated intratumoral spread of AdMdk-E1-iresTK-derived signals, which vanished after tumor eradication.


CONCLUSIONS
These data indicate that transcriptional targeting of viral replication by the Mdk promoter represents a promising general strategy for oncolytic virotherapy of cancers with up-regulated Mdk expression, including malignant mesothelioma.
Kubo
Shuji
S
Laboratory of Host Defenses, Institute for Advanced Medical Sciences, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan. s-kubo@hyo-med.ac.jp
Kawasaki
Yoshiko
Y
Yamaoka
Norie
N
Tagawa
Masatoshi
M
Kasahara
Noriyuki
N
Terada
Nobuyuki
N
Okamura
Haruki
H
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D016207:Cytokines / Q000235:genetics*; D005822:Genetic Vectors; D006801:Humans; D007267:Injections; D008654:Mesothelioma / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008819:Mice, Nude; D000078792:Midkine; D050130:Oncolytic Virotherapy; D011401:Promoter Regions, Genetic; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D016207:Cytokines; D000078792:Midkine; D013937:Thymidine Kinase