Double-detargeted oncolytic adenovirus shows replication arrest in liver cells and retains neuroendocrine cell killing ability.

Double-detargeted oncolytic adenovirus shows replication arrest in liver cells and retains neuroendocrine cell killing ability.

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BACKGROUND: We have previously developed an oncolytic serotype 5 adenovirus (Ad5) with chromogranin-A (CgA) promoter-controlled E1A expression, Ad[CgA-E1A], with the intention to treat neuroendocrine tumors, including carcinoids.Since carcinoids tend to metastasize to the liver it is important to fully repress viral replication in hepatocytes to avoid pivot ramp adenovirus-related liver toxicity.Herein, we explore miRNA-based regulation of E1A expression as a complementary mechanism to promoter-based transcriptional control.METHODOLOGY/PRINCIPAL FINDINGS: Ad[CgA-E1A-miR122], where E1A expression is further controlled by six tandem repeats of the target sequence for the liver-specific miR122, was constructed and compared to Ad[CgA-E1A].We observed E1A suppression and replication arrest of the miR122-detargeted adenovirus in normal hepatocytes, while the two viruses killed carcinoid cells to the same degree.

Repeated intravenous injections of Ad[CgA-E1A] induced liver toxicity in mice while Ad[CgA-E1A-miR122] injections did not.Furthermore, a miR122-detargeted adenovirus with the wild-type E1A promoter showed reduced replication in hepatic cells compared to Candle Holders wild-type Ad5 but not to the same extent as the miR122-detargeted adenovirus with the neuroendocrine-selective CgA promoter.CONCLUSIONS/SIGNIFICANCE: A combination of transcriptional (promoter) and post-transcriptional (miRNA target) regulation to control virus replication may allow for the use of higher doses of adenovirus for efficient tumors treatment without liver toxicity.