Brain Tumor Detection Using Urine Test Made Possible by DNA Catch-and-Release Isolation Method

The presence of cancer cells, such as brain tumors, is usually detected only after the symptoms start to appear. Conventional diagnosis methods include laboratory tests, imaging tools, and tumor biopsies. In most cases, they are identifying the presence of cancer cells, isis too late. By the time they are detected, the tumor is already in its advanced stage, so it becomes difficult to remove them by surgery. As a response to this challenge, a new technique for detecting brain tumors was developed by a team of Japanese researchers.

The Potential of Urine Test in Cancer Detection

Brain tumors are known for having cell-free DNA (cfDNA), described as small DNA particles released as the tumors restore their cells and get rid of the damaged ones. Macrophages clear up the cfDNA of the host, but in the case of tumors, the cells divide themselves very fast. As a result, excess leftover cfDNA is excreted in the urine.

The U.S. Food and Drug Administration has approved cell detection as a non-invasive method of checking for cancer in a person's body. It provides the key for screening, identification, and prognosis of cancer, as well as progression monitoring and determining the treatment response. However, there is no available technique for efficiently isolating cfDNA from urine because the excreted cfDNA is usually short, fragmented, and present in low concentration.

A Novel Nanowire Assay

Overcoming this problem has become the focus of a group of experts from Nagoya University in Japan in collaboration with other scientists from the University of Tokyo and the Institute of Technology Ladkrabang in Thailand. They developed a method to capture cfDNA and extracellular vesicles from a type of brain tumor called gliomas.

The technique created by the team involves capturing and releasing cfDNA on zinc dioxide (ZnO) nanowire surfaces from urine. Extracting this type of DNA allows them to detect IDH1 mutation successfully, which is considered the characteristic genetic mutation of gliomas.

Choosing ZnO is based on the fact that water molecules can adsorb on the surface of ZnO nanowires. The water molecules then bond hydrogen with any cfDNA in the urine sample. As the bonded cfDNA are washed out, researchers can isolate their trace amounts in a model.

Team member Professor Takao Yasui revealed that their group isolated urinary cfDNA, which is difficult to achieve with conventional techniques. Their previous experiment allowed their nanowire to capture cancer extracellular vesicles. Surprisingly, this similar technique also allowed them to capture cfDNA, enabling them to detect the IDH1 mutation. The result of their study is the first reported success in detecting IDH1 mutation from a urine sample with a volume as small as 0.5 mL.

Yasui is confident that their research sheds light on overcoming the failures of conventional cancer detection methods by offering state-of-the-art techniques for the clinical use of urinary cfDNA. Their chemical, biological, and nanotechnological techniques serve as analytical tools in facilitating early cancer diagnosis. Although the research was tested on gliomas, it also opens new possibilities in detecting the mutations of other types of tumors, particularly those that cannot be isolated using traditional techniques.

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