title: Development of a flexible and potent hypoxia-inducible promoter for tumor-targeted gene expression in attenuated Salmonella.
abstract: To increase the potential of attenuated Salmonella as gene delivery vectors for cancer treatment, we developed a hypoxia-inducible promoter system to limit gene expression specifically to the tumor. This approach is envisaged to not only increase tumor specificity, but also to target those cells that are most resistant to conventional therapies. We demonstrate that the exponential growth of the attenuated bacteria is identical under normoxia and hypoxia. A hypoxia-inducible promoter (HIP-1) was created from a portion of the endogenous Salmonella pepT promoter and was shown to drive reporter gene expression under both acute and chronic hypoxia, but not under normoxia. Genetic engineering of the TATA- and FNR-box within HIP-1 allowed fine-tuning of gene induction, resulting in hypoxic induction factors of up to 200-fold. Finally, we demonstrate that HIP-1 can drive hypoxia-mediated gene expression in bacteria which have colonized human tumor xenografts in mouse models. Expression of both GFP and RFP under control of HIP-1 demonstrated an approximately 15-fold increase relative to a constitutive promoter when tumors were made hypoxic. Moreover, the use of a constitutive promoter resulted in reporter gene expression in both tumors and normal tissues, whereas reporter gene expressing using HIP-1 was confined to the tumor.
authors.affiliation: Department of Radiation Oncology (Maastro Lab), GROW Research Institute, University of Maastricht, Maastricht, the Netherlands.
authors.forename: Asferd
authors.initials: A
authors.lastname: Mengesha
authors.forename: Ludwig
authors.initials: L
authors.lastname: Dubois
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: Willy
authors.initials: W
authors.lastname: Landuyt
authors.forename: Roland K
authors.initials: RK
authors.lastname: Chiu
authors.forename: Bradly G
authors.initials: BG
authors.lastname: Wouters
authors.forename: Jan
authors.initials: J
authors.lastname: Theys
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000693:Anaerobiosis / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D015972:Gene Expression Regulation, Neoplastic; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D045325:HCT116 Cells; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics* / Q000628:therapy*; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012475:Salmonella / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D023041:Xenograft Model Antitumor Assays
chemical_list: D018528:ATP-Binding Cassette Transporters; D007506:Iron-Sulfur Proteins; D014157:Transcription Factors; D010100:Oxygen