Scientists engineer bacteria to detect cancer DNA

Researchers working at the frontiers of advanced biological sensors have engineered bacteria that can detect the presence of tumour DNA in a living organism. This new technology, which detected cancer in the colons of mice, can pave the way for new biosensors that can be used to detect cancers, infections and other diseases.

In the past, researchers have used bacteria for many medical purposes, but this is the first time they have engineered it to identify specific DNA sequences and mutations outside of cells, according to the University of California, San Diego. “CATCH,” or the “Cellular Assay for Targeted CRISPR-discriminated Horizontal gene transfer” has been described in a research article published in the journal Science on Thursday.

“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. The detection of gastrointestinal cancers and precancerous lesions is an attractive clinical opportunity to apply this invention,” said co-author Jeff Hasty in a press statement. Hasty is a professor at the UC San Diego School of Biological Sciences and Jacobs School of Engineering.

Tumours often disperse their DNA into their surroundings. This DNA can be purified and analysed in labs but it is difficult to detect in the environments where it is released. To develop CATCH, the researchers engineered bacteria using CRISPR technology to test free-floating DNA sequences and compare them with predetermined cancer sequences.

According to the study’s first co-author Rob Cooper, many bacteria have a skill called natural competence where they can take up DNA from the environment. The researchers “employed” Acinetobacter baylyi, a bacteria with this skill, to detect cancer.

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A.baylyi was engineered using CRISPR technology to detect a mutated KRAS gene which helps colorectal cancer grow. When the engineered bacteria detect any of the mutated tumour DNA, it turns on an antibiotic resistance gene, which makes them resistant to a specific drug. Once researchers find bacteria that are resistant to the drug, they know that cancer has been detected.