Engineered Cancer Eating Bacteria Consume Tumors from Inside Out

Solid tumors often contain a core of dead cells that lacks oxygen, creating a unique microenvironment that differs from healthy tissue. While this oxygen-free center supports tumor survival, it also limits the effectiveness of many therapies. Certain bacteria can thrive only in environments without oxygen, making tumor cores an ideal niche. Researchers are now developing genetically engineered bacteria designed to colonize these oxygen-deprived regions and break down tumors from within, offering a novel biological approach to cancer treatment.

A research team, led by the University of Waterloo (Waterloo, ON, Canada), is working with Clostridium sporogenes, a soil bacterium that grows exclusively in oxygen-free environments and naturally targets the oxygen-depleted core of solid tumors. To overcome the limitation that the bacteria die when exposed to low oxygen levels at the tumor’s outer edges, researchers introduced a gene from a related oxygen-tolerant bacterium. They then engineered a timing mechanism using quorum sensing, a bacterial communication system that activates the oxygen-resistant gene only when sufficient bacteria have accumulated inside the tumor.

In one study, the team demonstrated that Clostridium sporogenes could be genetically modified to tolerate oxygen. In a follow-up study, they validated the quorum-sensing system by programming bacteria to produce a green fluorescent protein, confirming that gene activation occurred only when bacterial populations reached a critical threshold. The findings, published in ACS Synthetic Biology, show that the engineered system can function predictably, mimicking an electrical circuit built from DNA components. The research establishes proof of concept for combining oxygen resistance with controlled gene activation in tumor-targeting bacteria.

By enabling bacteria to survive longer at the tumor’s periphery while preventing growth in oxygen-rich areas such as the bloodstream, the approach aims to enhance safety and effectiveness. The engineered organisms are designed to selectively colonize tumors and consume nutrients within the cancerous tissue, potentially reducing tumor mass from the inside out. Researchers now plan to integrate both the oxygen-resistant gene and quorum-sensing control mechanism into a single bacterium and test the system in pre-clinical tumor models. If successful, the strategy could pave the way for a new class of synthetic biology-based cancer therapies.

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