Development of a melanoma-specific adenovirus.
Concerns regarding the hepatotoxicity of adenovirus for cancer gene therapy have led to attempts to engineer viruses for tissue-specific gene expression and tissue-specific replication. The Tyrex2 (a tandem murine melanocyte-specific enhancer) system was used to express luciferase, purine nucleoside phosphorylase (PNP), and the essential adenoviral gene E1A. In nonmelanoma cell lines, the CMV promoter/enhancer (CMV p/e) was 969 times stronger than the Tyrex2 construct, whereas in melanoma cells it was only 2.6 times stronger. An adenovirus with Tyrex2 regulating PNP (Ad2Tyr2-PNP) was tested for cytotoxicity. In melanoma cells, treatment with Ad2Tyr2-PNP plus the prodrug 6-methylpurine deoxyriboside (6-MPDR) resulted in 90% cytotoxicity by day 4. In non-melanoma cell lines, only the CMV p/e resulted in significant cytotoxicity. We compared the intrinsic E1A promoter/enhancer (E1A p/e) system with the melanoma-specific constructs and found that the Tyrex2 system achieved higher levels of luciferase than the E1A p/e in all melanoma lines tested. In non-melanoma cell lines, the E1A p/e is 12.4 times stronger than the Tyrex2 construct. Tyrex2 was then used to regulate adenoviral E1A expression to construct a melanoma-specific replicating adenovirus. We were unable to achieve selective replication. As E1A is a known transactivator of the adenovirus major late promoter (MLP), we studied the ability of the MLP to express a transgene in the context of tissue-selective E1A expression. We were able to demonstrate high levels of luciferase activity with this construct; however, selectivity was lost. Melanoma-specific adenovirus expression was achieved with the Tyrex2 construct, and this led to melanoma-specific cytotoxicity by the potent PNP suicide gene. Selective melanoma-specific replication was not successful. The MLP may be a useful promoter in the context of a tissue-specific replicating adenovirus.
McCart
J Andrea
JA
Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Wang
Zhong-Hui
ZH
Xu
Hui
H
Hu
Yun
Y
Park
Bernard
B
Alexander
H Richard
HR
Bartlett
David L
DL
D000256:Adenoviridae / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D017500:Adenovirus E1A Proteins / Q000235:genetics; D001483:Base Sequence; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000628:therapy / Q000821:virology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic
D017500:Adenovirus E1A Proteins