Leveraging dysregulated tumor metabolism for targeting anticancer bacteria.

Widespread application of bacterial-based cancer therapy is limited because of the need to increase therapeutic bacteria specificity to the tumor to improve treatment safety and efficacy. Here, we harness the altered tumor metabolism and specifically elevated kynurenine accumulation to target engineered bacteria to the cancer site. We cloned and leveraged kynurenine-responsive transcriptional regulator (KynR) with its cognate promoter in Escherichia coli. Optimizing KynR expression coupled with overexpressing kynurenine transporter and amplifying the response through plasmid copy number-based signal amplification enabled the response to kynurenine at the low micromolar levels. Knocking out genes essential for cell wall synthesis and supplying these genes via kynurenine-controlled circuits allowed tuning Salmonella enterica growth in response to kynurenine. Our kynurenine-controlled S. enterica (hereafter named AD95+) showed superior tumor specificity in breast and ovarian cancer murine models compared to S. enterica VNP20009, one of the best characterized tumor-specific strains. Last, AD95+ showed anticancer properties compared to vehicle controls, demonstrating the potential as an anticancer therapeutic.