Tumour-targeted delivery of TRAIL using Salmonella typhimurium enhances breast cancer survival in mice.
BACKGROUND
An effective cancer therapeutic must selectively target tumours with minimal systemic toxicity. Expression of a cytotoxic protein using Salmonella typhimurium would enable spatial and temporal control of delivery because these bacteria preferentially target tumours over normal tissue.


METHODS
We engineered non-pathogenic S. typhimurium to secrete murine TNF-related apoptosis-inducing ligand (TRAIL) under the control of the prokaryotic radiation-inducible RecA promoter. The response of the RecA promoter to radiation was measured using fluorometry and immunoblotting. TRAIL toxicity was determined using flow cytometry and by measuring caspase-3 activation. A syngeneic murine tumour model was used to determine bacterial accumulation and the response to expressed TRAIL.


RESULTS
After irradiation, engineered S. typhimurium secreted TRAIL, which caused caspase-3-mediated apoptosis and death in 4T1 mammary carcinoma cells in culture. Systemic injection of Salmonella and induction of TRAIL expression using 2 Gy gamma-irradiation caused a significant delay in mammary tumour growth and reduced the risk of death by 76% when compared with irradiated controls. Repeated dosing with TRAIL-bearing Salmonella in conjunction with radiation improved the 30-day survival from 0 to 100%.


CONCLUSIONS
These results show the pre-clinical utility of S. typhimurium as a TRAIL expression vector that effectively reduces tumour growth and extends host survival.
Ganai
S
S
Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA.
Arenas
R B
RB
Forbes
N S
NS
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D015151:Immunoblotting; D007150:Immunohistochemistry; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000382:microbiology* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D011401:Promoter Regions, Genetic; D011938:Rec A Recombinases / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism
D053221:TNF-Related Apoptosis-Inducing Ligand; D011938:Rec A Recombinases; D053148:Caspase 3