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Scientists genetically modified salmonella to eat cancerous tumors

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Vadim Guzhva/123RF
Everybody hates food poisoning. If you could wave a magic wand and rid the Earth of it in an instant, you’d totally do it, right?

Well, maybe not. Because as it turns out, a strain of food poisoning may just be our best ally in fighting an even worse enemy: Glioblastomas, aka one of the deadliest forms of brain cancer around.

According to a new research project carried out by biomedical engineers at Duke University, the bacterium Salmonella typhimurium can be tweaked to turn a nasty bug into a veritable “cancer-seeking missile.”

“Brain tumors are tough to treat because they invade brain tissue and don’t have a clear edge that allows neurosurgeons to remove all the tumor,” Ravi Bellamkonda, Vinik Dean of Duke’s Pratt School of Engineering, told Digital Trends. “The motivation for this study was to design a system that had the ability to seek out and localize to remote, metastatic tumors within the brain, and only express tumor killing proteins in those sites.”

So far, so intriguing. The really unique insight, however, was the decision to turn to food poisoning as the weapon of choice. In fact, despite its tendency for making people sick, salmonella is almost perfectly suited for this role — being a bacteria with the ability to move in dense tissue like the brain.

By adapting it to make it deficient in an essential building block for its survival, an organic compound called purine, salmonella suddenly acquires an insatiable taste for brain tumors.

Why? Because Purines are enriched in tumors, so this way the bacteria only finds a good supply of its much-needed foodstuff in enriched tumor regions.

“Next we engineered the tumor-killing cargo of these bacteria only to be expressed and released when the oxygen tension was low,” Bellamkonda continued. “It turns out because tumors grow rapidly, most of them have low oxygen tension. So the tumor killing proteins were only released by the bacteria in tumor regions. With this approach, we show a 20 percent cure rate, which is phenomenal for this challenging condition.”

The next phase of this project will involve answering some questions concerning the response rate to treatment, along with more analysis about how the work impacts on different subsets of tumor.

“We would like to probe and answer these questions so that we can then evaluate progress to human treatment,” Bellamkonda said.

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