Scientists genetically engineer bacteria to detect cancer cells

An international team of scientists has developed a new technology that can help detect (or even treat) cancer in hard-to-reach places, such as the colon. The team has published a paper in Science for the technique dubbed CATCH, or cellular assay for targeted, CRISPR-discriminated horizontal gene transfer. For their lab experiments, the scientists used a species of bacterium called Acinetobacter baylyi. This bacterium has the ability to naturally take up free-floating DNA from its surroundings and then integrate it into its own genome, allowing it to produce new protein for growth.  

What the scientists did was engineer A. baylyi bacteria so that they'd contain long sequences of DNA mirroring the DNA found in human cancer cells. These sequences serve as some sort of one-half of a zipper that locks on to captured cancer DNA. For their tests, the scientists focus on the mutated KRAS gene that's commonly found in colorectal tumors. If an A. baylyi bacterium finds a mutated DNA and integrates it into its genome, a linked antibiotic resistance gene also gets activated. That's what the team used to confirm the presence of cancer cells: After all, only bacteria with active antibiotic resistance could grow on culture plates filled with antibiotics. 

While the scientists were successfully able to detect tumor DNA in mice injected with colorectal cancer cells in the lab, the technology is still not ready to be used for actual diagnosis. The team said it's still working on the next steps, including improving the technique's efficiency and evaluating how it performs compared to other diagnostic tests. "The most exciting aspect of cellular healthcare, however, is not in the mere detection of disease. A laboratory can do that," Dan Worthley, one of the study's authors, wrote in The Conversation. In the future, the technology could also be used for targeted biological therapy that can deploy treatment to specific parts of the body based on the presence of certain DNA sequences. 

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