Cancer-eating bacteria engineered to consume tumors from the inside out
Original story from the University of Waterloo (Canada).
Researchers engineer bacteria capable of consuming tumors from the inside out.
A research team led by the University of Waterloo (Canada) is developing a novel tool to treat cancer by engineering hungry bacteria to literally eat tumors from the inside out.
“Bacteria spores enter the tumor, finding an environment where there are lots of nutrients and no oxygen, which this organism prefers, and so it starts eating those nutrients and growing in size,” explained Marc Aucoin, a chemical engineering professor at Waterloo. “So, we are now colonizing that central space, and the bacterium is essentially ridding the body of the tumor.”
Key to the approach is a bacterium called Clostridium sporogenes, which is commonly found in soil and can only grow in environments with absolutely no oxygen.
The core of a solid, cancerous tumor is comprised of dead cells and is oxygen-free, making it an ideal breeding ground for the bacterium to multiply.
But there is a biological catch: when the cancer-eating organisms reach the outer edges of tumors, they are exposed to low levels of oxygen and die without completing their mission to fully destroy them.
To solve that problem, the researchers first added a gene to the organism from a related bacterium that can better tolerate oxygen, enabling it to live longer near the outside of a targeted tumor.
They then found a way to activate the oxygen-resistant gene at just the right time – critical to preventing bacteria from inadvertently growing in oxygen-rich places such as the bloodstream – by leveraging a phenomenon known as quorum sensing.
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In simple terms, quorum sensing involves chemical signals released by bacteria. Only when many bacteria have grown in a tumor is the signal strong enough to turn on the oxygen-resistant gene, ensuring it doesn’t happen too soon.
In one study, researchers demonstrated that Clostridium sporogenes can be modified to tolerate oxygen. In a follow-up study, they tested their quorum sensing system by making bacteria produce a green fluorescent protein.
“Using synthetic biology, we built something like an electrical circuit, but instead of wires we used pieces of DNA,” commented Brian Ingalls, a professor of applied mathematics at Waterloo. “Each piece has its job. When assembled correctly, they form a system that works in a predictable way.”
Researchers now plan to combine the oxygen-resistant gene and the quorum-sensing timing mechanism in one bacterium and test it on a tumor in pre-clinical trials.
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