Research ArticleCancer

Programmable probiotics for detection of cancer in urine

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Science Translational Medicine  27 May 2015:
Vol. 7, Issue 289, pp. 289ra84
DOI: 10.1126/scitranslmed.aaa3519

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Synthetic bacteria for tumor detection

Tumors often harbor bacteria, and Danino et al. have taken advantage of this peculiar fact to design a method to detect liver metastases. An E. coli strain was carefully engineered to carry β-galactosidase, an enzyme that can metabolize numerous substrates. When fed to mice, these bacteria transited the gut epithelium to enter the bloodstream and then traveled to the liver, where they take up residence in any tumor colonies that are present. At that point, the mice were fed LuGal, a combined luciferin and galactose molecule. When the LuGal reached the bacteria in the tumors, the bacterial β-galactosidase metabolized it to luciferin, which was then excreted in the urine. The amount of luciferin, an easily detectible molecule, revealed the tumor burden carried in the liver. It remains to be seen whether this noninvasive approach to cancer detection can be applied to other tumor types and locations, but the versatility conferred by control of the enzymes in the E. coli and the substrates fed to the animal bodes well for future application.