title: Viral and nonviral factors causing nonspecific replication of tumor- and tissue-specific promoter-dependent oncolytic adenoviruses.
abstract: Restricted replication-competent adenoviruses (RRCAs) using tumor- and tissue-specific promoters (ttsP's) are new tools for cancer gene therapy. In this study we investigated viral and nonviral factors affecting "leakiness" of several ttsP's and their relevance for nonspecific ttsP-dependent RRCA (ttsP-RRCA) replication. The leakiness of the ttsP's in nontarget cells was per se highly variable and correlated with levels of nonspecific ttsP-RRCA replication. Transcriptional regulator elements fused to ttsP's showed variable effects: a hypoxic response element reduced leakiness of an alpha-fetoprotein promoter. In contrast, a mouse tyrosinase enhancer increased leakiness of a tyrosinase promoter, although it was not affected by a human tyrosinase enhancer. Furthermore, leakiness of ttsP's was enhanced by 5'-terminal adenoviral E1A enhancers, and adenoviral E1A-13S was found to be a strong transactivator of ttsP's, leading to "autoactivation" of leaky ttsP-RRCAs. In a proof-of-principle study, ttsP-RRCA replication was shown to be inhibited by a tetracycline-controlled transcriptional silencer via direct ttsP silencing. This opens up the prospect of pharmacological regulation of ttsP-RRCAs. Together, these data indicate that leakiness of ttsP's induced by several factors is a major cause of nonspecific ttsP-RRCA replication. Consideration of these factors may help optimize ttsP-dependent RRCA vectors and may thereby improve their safety.
authors.affiliation: Department of Cardiology and Pneumonology, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany.
authors.forename: Almudena
authors.initials: A
authors.lastname: Hurtado Picó
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Wang
authors.forename: Isaac
authors.initials: I
authors.lastname: Sipo
authors.forename: Ulrike
authors.initials: U
authors.lastname: Siemetzki
authors.forename: Jürgen
authors.initials: J
authors.lastname: Eberle
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Poller
authors.forename: Henry
authors.initials: H
authors.lastname: Fechner
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D017500:Adenovirus E1A Proteins / Q000235:genetics; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D020868:Gene Silencing; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics*; D006801:Humans; D014442:Monophenol Monooxygenase / Q000235:genetics; D009369:Neoplasms / Q000235:genetics*; D011401:Promoter Regions, Genetic; D013752:Tetracycline / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology; D014407:Tumor Cells, Cultured; D014779:Virus Replication / Q000187:drug effects / Q000235:genetics*; D000509:alpha-Fetoproteins / Q000235:genetics
chemical_list: D017500:Adenovirus E1A Proteins; D014157:Transcription Factors; D000509:alpha-Fetoproteins; D014442:Monophenol Monooxygenase; D013752:Tetracycline