Scientists engineer bacteria to detect colon cancer DNA in mice

Over 50,000 people died of colon cancer in 2020 in the US, a new innovation could pave the way for new biosensors that identify infections, cancers, and other diseases.
Sejal Sharma
Representational image of colon cancer
Representational image of colon cancer


“There’s a future where nobody need die of colorectal cancer,” said Dan Worthley, an Australian doctor who collaborated on a study with a team of US scientists to engineer a bacteria that can detect the presence of tumor DNA in a live organism.

Their innovation could pave the way for new biosensors which could identify infections, cancers, and other diseases. According to CDC, cancer is the second leading cause of death in the US, after heart disease. One of every five deaths in the United States is due to cancer.

In 2020 alone, 126,240 cases of colon cancer were reported, and 51,869 people died of this cancer.

The team designed CATCH

The team’s design, which they are calling CATCH - Cellular Assay for Targeted CRISPR-discriminated Horizontal gene transfer - engineered a bacteria using CRISPR technology, which enables scientists to edit the DNA of any genome. The team then tested DNA sequences surrounding a tumor and compared them with predetermined cancer sequences, a statement by the scientists explained.

The researchers carried out their experiments in an animal model, which detected cancer in the colons of mice. Cancerous tumors shed their DNA in the environments around them. “Many bacteria can take up DNA from their environment, a skill known as natural competence,” said Rob Cooper, the study’s co-first author.

Bacterias are already present in the colon. So the team worked on deploying engineered bacteria that will act as biosensors inside the gut and detect DNA released from colorectal tumors. 

“As we started on this project four years ago, we weren’t even sure if using bacteria as a sensor for mammalian DNA was even possible,” said Jeff Hasty, team leader of the study and a professor at the UC San Diego School of Biological Sciences and Jacobs School of Engineering. 

“The detection of gastrointestinal cancers and precancerous lesions is an attractive clinical opportunity to apply this invention,” he added.

Cooper identified a bacteria called Acinetobacter baylyi, which had the elements necessary for both taking up DNA and using CRISPR to analyze it, he explained in the press release.

The researchers designed, built, and tested the Acinetobacter baylyi bacteria as a sensor to detect DNA from KRAS, a gene that is mutated in many cancers. They found that their engineered bacteria were taking up mutant forms of KRAS.

“It was incredible when I saw the bacteria that had taken up the tumor DNA under the microscope. The mice with tumors grew green bacterial colonies that had acquired the ability to grow on antibiotic plates,” said Wright.

Refining new innovation

This may be of value in clinical and commercial applications – wherever and whenever, the detection of DNA is valuable.

Associate Professor Siddhartha Mukherjee of Columbia University, who was not involved in the study, indicated that in the future, “disease will be treated and prevented by cells, not pills. A living bacterium that can detect DNA in the gut is a tremendous opportunity to act as a sentinel to seek and destroy gastrointestinal, and many other, cancers.”