DNA detectors find cancer
Researchers at Duke University have created simple detectors from interacting strands of synthetic DNA that are tens of thousands of times thinner than a human hair. These circuits work by attaching to the outer shell of the cell and analyzing it for the presence of specific proteins. If the device finds the target protein, it marks the cell with a small glowing label.
Since the DNA schema distinguishes between cell types with higher specificity than existing methods, the researchers hope that their work can improve the diagnosis and treatment of cancer.
Similar methods have been used to detect cancer before, but they often gave false positive results – they mistakenly found cancer where there is none. This was due to the content in the cells of one or more of those proteins that the DNA chain perceived as targeted, but no cell type had all the target proteins on the surface at the same time. For every correctly detected cancer cell, there was a group of healthy cells mistakenly labeled as cancerous.
Each type of cancer cell has a characteristic set of cell membrane proteins on its surface. To reduce the number of errors, a group of researchers led by John Reif has developed a DNA scheme that should be attached to a specific combination of proteins in one cell. As a result, the device marks healthy cells less often.
This technology can be used as a cancer screening tool with fewer unnecessary follow-up examinations. In addition, it will help develop a more targeted cancer treatment with fewer side effects.
Each basic element of the DNA circuit consists of two strands of DNA. The first strand of DNA folds and partially connects to itself, forming the shape of a hairpin. The ends of this hairpin are connected to the second DNA chain, which is folded in the form of a lock and a thread coming from it corresponding to a certain protein on the cell surface, like puzzle pieces.
To find a cancer cell, the components of the DNA scheme must be introduced into the medium with a sample of cells taken from the patient. If any cells contain a target combination of proteins on the membrane, the entire device will attach to it. The addition of an initiating DNA chain leads to the opening of one of the pins, which, in turn, triggers another, and so on until the last hairpin in the chain opens and the cell begins to glow.
Tests of the device in Reif's laboratory have shown that it can be used to detect leukemia cells and distinguish them from other cancers by the strength of the glow.
The researchers note that the devices can be easily reconfigured to detect different cell surface proteins by replacing the filaments. In the future, Reif plans to refine the device so that it can release a small molecule that warns the body's immune system about the presence of cancer cells.
The researchers write that their DNA circuits require testing under more realistic conditions to make sure they are tagging the right cells. But it is already clear that this is a promising step in the direction of informed diagnosis and targeted treatment.
Article T.Song et al. Programming DNA-Based Biomolecular Reaction Networks on Cancer Cell Membranes is published in the Journal of the American Chemical Society.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on Duke Today: Tiny devices made of DNA could detect cancer with fewer false alarms.