Researchers at the University of Waterloo have developed a novel cancer treatment using engineered bacteria that consume tumors from the inside. The team modified a common soil bacterium to target and destroy the oxygen-free core of solid cancers.
The approach uses Clostridium sporogenes, a bacterium that only grows in environments with no oxygen. The center of solid tumors consists of dead cells and lacks oxygen, making it an ideal breeding ground for the bacteria to multiply and consume nutrients.
Dr. Marc Aucoin, a chemical engineering professor at Waterloo, explained that bacterial spores enter the tumor and find a nutrient-rich, oxygen-free environment where they thrive. “It starts eating those nutrients and growing in size,” he said. “We are colonizing that central space, and the bacterium is essentially ridding the body of the tumor.”
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The key challenge was that when the cancer-eating organisms reach the outer edges of tumors, they encounter low oxygen levels and die before completing their mission. The research team solved this by adding a gene from a related bacterium that can better tolerate oxygen, allowing it to survive longer near the tumor’s edges.
They then developed a timing mechanism using quorum sensing—a process where bacteria release chemical signals that only activate the oxygen-resistant gene when enough bacteria have gathered inside the tumor. This prevents the bacteria from growing in oxygen-rich areas like the bloodstream.
Dr. Brian Ingalls, a professor of applied mathematics at Waterloo, compared the system to an electrical circuit built from DNA pieces. “Each piece has its job,” he said. “When assembled correctly, they form a system that works in a predictable way.”
In one study, researchers proved Clostridium sporogenes could be modified to tolerate oxygen. A follow-up study tested the quorum sensing system by making bacteria produce a green fluorescent protein, confirming the timing mechanism worked as designed.
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The technology is still in development. Researchers now plan to combine both modifications in one bacterium and test it on tumors in pre-clinical trials. The project grew from work by PhD student Bahram Zargar, who collaborated with Waterloo’s interdisciplinary team of engineers, mathematicians, and life scientists.
This approach represents a fundamentally different way to fight cancer. Rather than attacking tumors with chemicals or radiation from outside, it uses engineered life forms to consume malignancies from within, turning the tumor’s own environment against it.
