Cancer treatments such as surgery, chemotherapy, and radiation have saved many lives, but they also have limits and side effects. Scientists around the world are searching for new ways to attack tumors more precisely while causing less harm to healthy tissue.
A research team at the University of Waterloo is exploring an unusual but promising approach: using specially engineered bacteria to destroy tumors from the inside.
The idea may sound surprising, but it is based on a simple biological fact. Many solid tumors have a core that lacks oxygen. As tumors grow quickly, they often outpace their blood supply.
Without enough blood vessels, the inner parts of the tumor become low in oxygen and filled with dead cells and nutrients. These conditions are difficult for most human cells but ideal for certain types of bacteria that thrive in oxygen-free environments.
The researchers focused on a bacterium called Clostridium sporogenes, which is commonly found in soil. This microbe can only survive where there is no oxygen.
Because of this, it naturally targets the inner core of tumors while leaving healthy tissues alone, since normal tissues contain oxygen. Once inside the tumor, the bacteria begin to grow and consume nutrients, gradually breaking down the cancerous mass.
However, the approach faces an important challenge. Tumors are not completely oxygen-free. While the center has little oxygen, the outer regions closer to blood vessels contain small amounts.
When the bacteria spread toward these areas, they encounter oxygen and begin to die before the tumor is fully destroyed. To overcome this barrier, the scientists modified the bacteria by adding a gene from a related species that can tolerate low levels of oxygen.
This modification allows the engineered bacteria to survive longer as they move outward, potentially enabling them to attack more of the tumor.
But safety is a major concern. If the bacteria were able to survive too well in oxygen-rich areas, they could spread beyond the tumor and cause harm. To prevent this, the researchers designed a clever control system using a natural bacterial communication method known as quorum sensing.
Quorum sensing allows bacteria to sense how many of them are present in a given area. Each bacterium releases chemical signals, and when enough bacteria gather, the signals reach a level that triggers specific genes to turn on.
The scientists programmed the bacteria so that the oxygen-tolerance gene activates only after a large number of bacteria have accumulated inside the tumor. This ensures the survival mechanism is switched on only where it is needed.
To test whether their system worked, the team used synthetic biology techniques to create DNA circuits that function like tiny biological programs. They first programmed the bacteria to produce a glowing green protein when the system activated. Observing the glow confirmed that the bacteria turned on the gene at the correct time.
This research is still in early stages, and the next step will be testing the fully engineered bacteria in pre-clinical studies. If successful, the approach could lead to a new type of cancer therapy that targets tumors with high precision. Unlike traditional treatments, bacteria-based therapy could reach parts of tumors that are difficult for drugs or radiation to penetrate.
In analyzing the study, the strategy is innovative because it takes advantage of a tumor’s own weaknesses rather than trying to destroy it from the outside.
However, many questions remain about safety, effectiveness, and how the immune system will respond. Extensive testing in animals and eventually humans will be required before the method could become a standard treatment.
Even so, the concept highlights how advances in genetic engineering and microbiology are opening new possibilities in medicine.
Using living organisms as tools to fight disease represents a shift in how scientists think about treatment. If future research confirms its promise, engineered bacteria could become a powerful weapon against cancers that are currently difficult to treat.
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The study is published in ACS Synthetic Biology.
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