Abstract A137: Chemotherapy molecule delivered by tumor-targeted salmonella enterica serovar typhimurium under the control of integrated modular gate

Abstract

Abstract Several strictly or facultative anaerobic bacteria have attracted more and more attention in cancer therapeutics because of their targeting and accumulating abilities in solid tumors, and Salmonella enterica serovar Typhimurium is one of them. These bacteria were also adapted to deliver therapeutic factors and were applied alone or in combination with conventional therapeutics. The aim of this study is to test a new integrated gene expression system in S. Typhimurim SL1344, and the benefit of the new system in amplifying therapeutic molecule production during bacterium targeting and accumulating in solid tumor. We have constructed a synthetic genetic gate in S. Typhimurim SL1344 that integrates information from two promoters as inputs and actives a promoter output only when both input promoters are induced. The integration occurs via an interaction between L-arabinose concentration and bacterium cell density. When certain amount of L-arabinose were added in the system and bacterium population were higher enough, the tumor necrosis factor apoptosis inducing ligand(TRAIL) and fluorescent protein ZsGreen as the control were produced by bacteria. LS174T colon carcinoma cells were processed to form cylindroids between the bottom surface of a 96-well plate and the top surface of a set of polycarbonate cylindrical plugs attached to a polycarbonate lid to mimic solid tumor, and then cylindroid cultures were inoculated with S. typhimurium SL1344 carrying TRAIL or ZsGreen expression system. 0.2% (w/v) L-arabinose was added into the well after 12hr inoculation, and then washed out after 2hr induced. Extents of apoptosis in cylindroids were tested by caspase-3 activity assay. Results showed that the bacteria accumulated inside cylindroids indicated by ZsGreen expression, and the average normalized intensity of apoptotic cell was higher in the cylindroids inoculated by the bacteria carrying the TRAIL than those inoculated by the bacteria carrying the ZsGreen. It can be concluded that the constructed integrated modular gate could effectively control bacteria to produce functional chemotherapy molecule in solid tumor at desirable time and places. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A137.