Cancer-specific metabolites as cues to engineer and target anti-tumor therapeutic bacteria

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Abstract With the ongoing advances in synthetic biology, the application of therapeutic bacteria for cancer treatment is now closer to becoming a reality. Achieving this goal, however, still needs better targeting of the therapeutic bacteria towards the cancer sites to improve the efficacy and safety of the treatment. Here, we propose to use a key cancer metabolite produced in colorectal cancers and other tumors as a cue to activate genetic circuits inside the therapeutic bacteria to control those bacteria and target them to the cancer site. To achieve this goal, we are going to clone the naturally occurring transcriptional regulator for this metabolite into engineered therapeutic E. coli and optimize its performance. In parallel, we will employ specific RNA aptamers which we already developed for this metabolite, to build synthetic riboswitches to control protein expression in the engineered Escherichia coli strain. Subsequently, these two tools; the transcription regulator, and the synthetic riboswitches, will be used in combination to build genetic circuits inside the engineered E. coli strain. These genetic circuits will then 1) Direct the engineered E. coli (along this key metabolite concentration gradient) towards the tumor site through controlling its motility, 2) Induce the attachment of this E. coli to the tumor cells, and 3) Induce the production of a therapeutic molecule within the tumor microenvironment in response to this key metabolite. During the time frame of this grant, we will be working on developing these E. coli genetic circuits which can respond to this metabolite at the physiologically relevant concentrations and we are going to test these engineered E. coli on cancer cell lines. Future work, which will be pursued through subsequent grants, will involve trying these engineered bacteria in mice models for colon cancer.