title: The engineered Salmonella typhimurium inhibits tumorigenesis in advanced glioma.
abstract: OBJECTIVE
  To explore the antitumor role of the attenuated Salmonella typhimurium ΔppGpp with inducible cytolysin A (ClyA) in advanced stage of glioma.
  
  
  METHODS
  The C6 rat glioma cells were orthotopically implanted by surgery into the caudate nucleus of rat brains. The rats were then randomly divided into the treatment group (SL + ClyA) (n=12), negative control group (SL) (n=12), and control group (phosphate-buffered saline [PBS]) (n=12). In the treatment group, the attenuated S. typhimurium were transformed with the plasmid-encoded antitumor gene ClyA. The expression of ClyA was controlled by the TetR-regulated promoter in response to extracellular doxycycline. The plasmid also contained an imaging gene lux to allow illumination of the tumor infected by the bacteria. The rat glioma C6 cells were implanted into the caudate nucleus of all rats. The engineered S. typhimurium and respective controls were injected intravenously into the rats 21 days after initial tumor implantation. The pathological analysis of the glioma tumor was performed at 21 days and 28 days (7 days after doxycycline treatment) postimplantation. All rats underwent MRI (magnetic resonance imaging) and bioluminescence study at 21 days and 28 days postimplantation to detect tumor volume. The differences between the three groups in tumor volume and survival time were analyzed.
  
  
  RESULTS
  Advanced stage glioma was detected at 21 days postimplantation. Bioluminescence showed that the engineered S. typhimurium accumulated in glioma tumors and disappeared in the normal reticuloendothelial tissues 3 days after intravenous injection. MRI showed that the tumor volume in the S. typhimurium with ClyA group were significantly reduced compared to the bacteria alone and no bacteria groups 7 days post-doxycycline treatment (P<0.05), while the necrotic tumor volume in the S. typhimurium with ClyA group and S. typhimurium alone group increased significantly compared to the control group (P<0.01). In addition, the survival time was significantly prolonged in the bacteria-treated group compared to the PBS-treated control group (P<0.01).
  
  
  CONCLUSIONS
  The engineered S. typhimurium can significantly induce cancer cell apoptosis in the tumor center and inhibit cancer cell proliferation in the outer zone of advanced glioma tumor, leading to a prolonged survival time in rats. In addition, the engineered S. typhimurium that carried the antitumor and imaging genes controlled by the TetR-regulated promoter have high delivery efficiency with tolerable side effects in rats.
authors.affiliation: Department of Radiology, The Third Xiangya Hospital, Central South University, Changsha, People's Republic of China.
authors.forename: Jian-Qiang
authors.initials: JQ
authors.lastname: Chen
authors.affiliation: Department of Radiology, Affiliated Haikou Hospital of Xiangya School of Medicine, Central South University, Haikou, Hainan, People's Republic of China.
authors.forename: Yue-Fu
authors.initials: YF
authors.lastname: Zhan
authors.affiliation: Department of Radiology, The Third Xiangya Hospital, Central South University, Changsha, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Radiology, Affiliated Haikou Hospital of Xiangya School of Medicine, Central South University, Haikou, Hainan, People's Republic of China ; Department of Nuclear Medicine, Affiliated Haikou Hospital of Xiangya School of Medicine, Central South University, Haikou, Hainan, People's Republic of China.
authors.forename: Sheng-Nan
authors.initials: SN
authors.lastname: Jiang
authors.affiliation: Department of Radiology, Affiliated Haikou Hospital of Xiangya School of Medicine, Central South University, Haikou, Hainan, People's Republic of China.
authors.forename: Xiang-Ying
authors.initials: XY
authors.lastname: Li
keywords: Salmonella typhimurium; advanced glioma; brain tumor; cytolysin A