"Exosomes," granular substances released by cells, have been found to play various roles, including intercellular communication. Professor Takao Yasui at the School of Life Science and Technology at the Institute of Science Tokyo, developed technology to capture exosomes in urine and analyze specific microRNAs they contain for cancer risk screening. He co-founded the startup Craif with Chief Executive Officer (CEO) Ryuichi Onose to commercialize this technology. The company's product, "miSignal," which they develop and sell, has been adopted by medical institutions, corporations, and drugstores, and its online sales to individuals are also growing, showing promise for contributing to a healthy society.
Decoding "letters" from cells: Role in cancer metastasis revealed
Exosomes, granular substances measuring approximately 40 to 200 nanometers in diameter (nano means one billionth) secreted by cells, were once thought to be waste materials wrapped in lipid membranes and expelled by cells. However, recent research has revealed that surface membrane proteins determine selectivity for cellular uptake, and exosomes contain in their inside nucleic acids such as microRNA that transmit information between cells, between organisms, and throughout biological systems.
"If the lipid membrane of an exosome is an 'envelope,' then the microRNA inside is the 'letter,'" explains Yasui. MicroRNA was once considered useless because it only has 22 to 25 bases and does not produce proteins. However, Dr. Victor Ambros and Dr. Gary Ruvkun, who received the 2024 Nobel Prize in Physiology or Medicine, discovered that microRNA plays a crucial role in biological growth by regulating the expression of proteins produced by messenger RNA (Figure 1). To date, more than 2,000 types of microRNA have been found in humans, and various types of information are transmitted between cells daily.
MicroRNA is also closely involved in the mechanisms of cancer occurrence, progression, and metastasis. Unique microRNA in exosomes released by cancer cells reaches other tissues in the body and alters the environment at metastatic sites before cancer cells metastasize. Focusing on these characteristics of microRNA, Yasui developed technology to efficiently capture exosomes from urine and extract microRNA, and co-founded Craif with Onose. The service provided by the company, which enables highly accurate cancer risk screening using urine, is currently used by more than 1,500 medical institutions and corporations and is also sold at drugstores nationwide and online.
Using urine instead of blood: Efficient separation methods a challenge
Since his student days, Yasui has been interested in new analytical chemistry using nanostructures and control technologies for biologically related molecules. After finishing graduate school, he worked on DNA analysis using Christmas tree-shaped nanodevices. While advancing his research, he focused on the work of Professor Takahiro Ochiya, Specially Appointed Professor at the Institute of Medical Science, Tokyo Medical University, who was then affiliated with the National Cancer Center. He thought that if microRNA in exosomes could be captured and analyzed using nanodevices, early cancer detection might be possible.
Yasui says he initially intended to use blood for exosome collection. "The student I asked to do the experiment said they were reluctant to work with blood experiments, so we tried experimenting with urine, and the data turned out to be better than expected." Later, exosomes in blood were also analyzed, but urine yielded better analysis results. Above all, urine-based testing has the major advantage of being much easier compared with blood testing.
However, the challenge here was how to efficiently separate exosomes. Exosomes in urine are said to be fewer than those in blood. Exosomes are characterized by their density, size, and surface charge. Conventionally, they were separated using centrifugal force or aggregation, but the capture efficiency of about 30 percent posed a barrier.
Developing nanowires with high capture efficiency: Co-founding a company two months after meeting
Yasui focused on surface charge, one of the characteristics of exosomes, and considered separating exosomes from urine using oxide nanowires. Under pH 7 conditions close to body fluids, he tested changing the surface oxide material of the nanowires from silicon oxide to titanium oxide to zinc oxide so that the surface would be positively charged from negative. He found that zinc oxide nanowires with positively charged surfaces had the best capture efficiency.
Furthermore, by utilizing the fact that adding ammonia during the crystal growth of zinc oxide nanowires changes the morphology of the nanowires, he determined the morphology that could efficiently capture exosomes. He developed a nanodevice that comprehensively captures exosomes by combining the zinc oxide nanowires thus produced with microchannels (Figure 2), making it possible to capture exosomes with 99 percent efficiency. The development of this device was carried out through JST's PRESTO program, and a paper was published in December 2017. In January of the following year, he was immediately approached by JST's startup support department and venture capital firm ANRI about establishing a startup. Yasui declined, saying he could not be CEO, but in March he was introduced to someone who wanted to be a startup CEO. That person was Onose. Yasui and Onose hit it off and co-founded Craif in May 2018. It was an exceptional speed of less than two months from first meeting to founding.
Launching kit sales four years after establishment: Achieving AI analysis of microRNA
Before meeting Yasui, Onose says that when he was considering what to focus on when starting his own business, he realized that "cancer" was a theme that could contribute to human progress and have social impact. Losing his grandparents to cancer also encouraged his business development. "When I met Dr. Yasui through the venture capital firm ANRI, I had the intuition that this technology would change society. From there, time passed in a flash as we established the company." In addition to ANRI, JST's SUpport program of Capital Contribution to Early-Stage companies (SUCCESS) also invested in the establishment. "JST's participation in the investment gave us great peace of mind," Onose recalls.
However, there were many difficulties. "Providing technology that succeeded in the laboratory as a service for the general public has similar difficulties to reproducing a delicious restaurant's secret recipe in your home kitchen," says Mr. Onose. He notes that he struggled to create a system that would allow non-researchers to reproduce tricks for work that had not been verbalized, such as the techniques of skilled researchers.
After overcoming various difficulties, in February 2022, about four years after the company's establishment, they began offering products in the "miSignal" series of test kits to detect cancer risk and enable early detection. Currently, there are four product types in the miSignal series, and, notably, "miSignal Scan" (Figure 3) is the world's first technology to analyze microRNA in urine using machine learning with artificial intelligence (AI) (Figure 4). It can screen for the risk of up to 10 types of cancer, including pancreatic and ovarian cancers, which are considered difficult to detect early (Figure 5).
A society where everyone lives a full life: Equalizing life opportunities through medicine
One of Craif's future challenges is to increase the types of cancers that can be tested for, such as cervical cancer, uterine cancer, and liver cancer. Onose says he wants to expand to risk assessment for dementia and diabetes, in addition to cancer. Eventually, by implementing miSignal in toilets, "smart toilets" that can assess health risks may be realized. Preparations for overseas expansion are also underway. In the United States, an ecosystem of biotech startups has been established, and there is abundant talent. Craif is also expanding its overseas offices and is aiming for early service launch: "while improvements tailored to the sales region are necessary, such as developing algorithms adapted to different races, our strength is that we already have a base product, so we're not starting from zero."
Yasui is advancing new research on exosome capture using cellulose nanofibers. By collecting exosomes with nanofibers from tissues throughout the body of cancer patients and measuring microRNA for each organ, it may be possible to find microRNA close to the primary cancer site. If the properties and behavior patterns of cancer cells can be understood more deeply through such research, medicine will become more effective.
Craif, whose vision is "Realizing a world of peaceful longevity," derives its company name from combining the two words Crane (a symbol of longevity) and Life. In current medicine, most people go to the hospital only after symptoms appear and start treatment after being diagnosed with a disease. However, there must be changes in the body even before symptoms appear, and if the possibility of disease can be pointed out at that stage, preventive measures should be possible. "Medicine equalizes life opportunities. If we overcome cancer, this will become a world where everyone can live long lives," Mr. Onose stated his vision.
(Article: Keiichi Motohashi, Photography: Erika Shimamoto)
