title: Targeted deletion of the ara operon of Salmonella typhimurium enhances L-arabinose accumulation and drives PBAD-promoted expression of anti-cancer toxins and imaging agents.
abstract: Tumor-specific expression of antitumor drugs can be achieved using attenuated Salmonella typhimurium harboring the PBAD promoter, which is induced by L-arabinose. However, L-arabinose does not accumulate because it is metabolized to D-xylulose-5-P by enzymes encoded by the ara operon in Salmonellae. To address this problem, we developed an engineered strain of S. typhimurium in which the ara operon is deleted. Linear DNA transformation was performed using λ red recombinase to exchange the ara operon with linear DNA carrying an antibiotic-resistance gene with homology to regions adjacent to the ara operon. The ara operon-deleted strain and its parental strain were transformed with a plasmid encoding Renilla luciferase variant 8 (RLuc8) or cytolysin A (clyA) under the control of the PBAD promoter. Luciferase assays demonstrated that RLuc8 expression was 49-fold higher in the ara operon-deleted S. typhimurium than in the parental strain after the addition of L-arabinose. In vivo bioluminescence imaging showed that the tumor tissue targeted by the ara operon-deleted Salmonella had a stronger imaging signal (~30-fold) than that targeted by the parental strain. Mice with murine colon cancer (CT26) that had been injected with the ara operon-deleted S. typhimurium expressing clyA showed significant tumor suppression. The present report demonstrates that deletion of the ara operon of S. typhimurium enhances L-arabinose accumulation and thereby drives PBAD-promoted expression of cytotoxic agents and imaging agents. This is a promising approach for tumor therapy and imaging.
authors.affiliation: a Department of Nuclear Medicine ; Chonnam National University Medical School and Hwasun Hospital ; Jeonnam , Republic of Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Hong
authors.forename: Daejin
authors.initials: D
authors.lastname: Lim
authors.forename: Geun-Joong
authors.initials: GJ
authors.lastname: Kim
authors.forename: Seung-Hwan
authors.initials: SH
authors.lastname: Park
authors.forename: Hyeon
authors.initials: H
authors.lastname: Sik Kim
authors.forename: Yeongjin
authors.initials: Y
authors.lastname: Hong
authors.forename: Hyon E
authors.initials: HE
authors.lastname: Choy
authors.forename: Jung-Joon
authors.initials: JJ
authors.lastname: Min
mesh_terms: D000818:Animals; D001089:Arabinose / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000473:pathology / Q000628:therapy; D049410:Luciferases, Renilla / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009876:Operon; D054353:Perforin / Q000235:genetics / Q000627:therapeutic use / Q000633:toxicity; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000627:therapeutic use / Q000633:toxicity; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development; D014184:Transplantation, Homologous
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; D054353:Perforin; D001089:Arabinose; D049410:Luciferases, Renilla
keywords: L-arabinose; PBAD promoter; Salmonella typhimurium; ara operon; bacterial cancer therapy; bioluminescence; cytolysin A