One of the most important issues in cancer therapy is the specificity of drug delivery to tumor site. Many of the usual cancer treatment methods cannot cover this requirement and new strategies are needed. In these new methods some carriers are used to transfer drugs or genes of interest specifically to tumor cells. Bacteria are one of the most popular gene carriers. Bacterial vectors should be able to localize and grow in tumors. In this study, E. coli DH5α was used to deliver the gene of interest to the tumor site. For this purpose, E. coli DH5α which is capable of colonization in tumor site, was transformed with a plasmid carrying Lux gene cascade for tracing the bacteria. Oxidation of luciferine by luciferase which is encoded by Lux gene, leads to luminescent emission. In the next step, breast cancer was induced in female BALB/c mice with 4T1 cells and then transformed bacteria were intravenously injected. On day 4 after injection of bacteria, mouse was sacrified and tissue homogenates were prepared. The luminescent emission of homogenate suspensions were evaluated by a luminometer. The light emission of tumor suspension was 11000 folds higher than other tissues, including spleen, stomach, kidney, small intestine, colon and liver. Using this system, confirmed aggregation of transformed E. coli DH5α in Breast tumor cells. This outstanding feature can be used for specific drug or gene delivery to tumor locations in future studies in order to reduce offtarget toxicity of these agents.

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