Abstract
1440
Objectives: We have reported that genetically engineered bioluminescent E. coli specifically target cancers. In this study, our group exploited that genetically engineered bioluminescent E. coli and Salmonella typhimurium selectively target and proliferate in the breast cancer in vivo by employing optical bioluminescence imaging technique. Methods: pUC19 plasmid encloning Lux/GFP,was transformed into E. coli strains (DH5α) generating bioluminescent E. coli. To generate bioluminescent S. typhimurium, lux transposon cassette was integrated onto its chromosome. Breast cancer models were generated by direct inoculation of 4T1 (highly metastatic cells) and 4T7 (negative control) murine breast cancer cell lines into the abdominal mammary fat pad of BALB/c mice. Bacteria were intravenously injected into the tumor bearing mice. Results: We found the minimal number of the subcutaneously injected bacteria required for imaging by cooled CCD camera (IVIS100, Xenogen) was 1x106 for DH5α and 1x103 for S. typhimurium, and the intensity directly correlated with the number of bacteria up to 109 colony forming unit, CFU. The lowest dose of intravenously injected DH5α and S. typhimurium to visualize cancer was 1x107 and 1x106 CFU, respectively. The imaging signal from DH5α was detected initially in the liver but diminished from the next day. The bioluminescence of DH5α and S. typhimurium was observed in the breast cancer from 2nd day after injection. Conclusions: The bacterial bioluminescence was observed in the liver, spleen, and bones of established metastatic models with 4T1 cells. All the metastatic lesions were confirmed histologically. E. coli and S. typhimurium strongly targeted primary breast cancer as well as metastases. Chromosome-bsed lux expression strain (S. typhimurium) revealed stronger bioluminescence than plasmid-based lux expressing strain (DH5α). Live attenuated strains are applied for developing cancer targeting delivery vehicle.
- Society of Nuclear Medicine, Inc.