Imagine recruiting a strain of gut bacteria to help target and kill cancer cells in your colon? A team from the National University of Singapore (NUS) is doing exactly that – genetically modifying a common type of gut bacteria so it locks onto colorectal cancer cells and turns a substance found in broccoli into a cancer-killing toxin.

This remarkable research starts with genetically modifying a harmless form of bacteria commonly found in our gut called E. coli Nissle. The bacteria is engineered to bind to a compound called heparan sulphate proteoglycan, which is found on the surface of colorectal cancer cells.

The microbe lands on the cancer cells and then sits waiting for its host to consume a foodstuff containing glucosinolates. Found in broccoli, cabbage and other cruciferous vegetables, the glucosinolates are converted into a molecule called sulphoraphane – a known cancer-killing compound – via an enzyme secreted from the engineered bacteria.

The study first tested the process in vitro and found the combination of engineered bacteria and glucosinolates killed over 95 percent of colorectal cancer cells. Moving to mouse models the results were equally impressive, reducing tumor numbers by a striking 75 percent.

There are of course plenty of hurdles to overcome before this kind of research is ever practically implemented in human beings. Not the least of which are questions over the unintended side effects of seeding a human subject with genetically engineered bacteria. There are teams currently working on producing a "fail-safe" system for genetically engineered bacteria, similar to a kind of kill-switch, in case the bacteria start behaving in an unintended way.

The NUS team sees a future where these engineered bacteria are consumed as probiotics either to prevent cancer, or to kill lingering tumor cells that were too small to be identified during a surgical removal. Eating your broccoli could literally become a medical necessity.

"One exciting aspect of our strategy is that it just capitalizes on our lifestyle, potentially transforming our normal diet into a sustainable, low-cost therapeutic regimen," says Matthew Chang, one of the researchers on the project.

The research was published in the journal Nature Biomedical Engineering.

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