The discovery of new biomarkers is important for detecting ovarian cancer, as the disease is difficult to detect in its early stages where it can most easily be treated.

One approach to detecting cancer is to look for extracellular vesicles (EVs), especially small proteins released from the tumor called exosomes. As these proteins are found outside the cancer cell, they can be isolated from body fluids, such as blood, urine, and saliva. However, the use of these biomarkers is hindered by the lack of reliable ones for the detection of ovarian cancer.

A research group led by Akira Yokoi (he, him) of the Nagoya University Graduate School of Medicine and Mayu Ukai (she, her) at the Institute for Advanced Research extracted both small and medium/large EVs from high-grade serous carcinoma (HGSC), the most common type of ovarian cancer, and analyzed them using liquid chromatography-mass spectrometry to analyze the proteins.

Extracellular vesicles (EVs) are vesicles with lipid-bilayer structures (shown in center), and three proteins expressed on small EVs called exosomes (shown in red, green, blue) are more suitable biomarkers to detect ovarian cancer than the larger extracellular vesicle. Credit: Akira Yokoi

Initially their research was challenging. “The validation steps for the identified proteins were tough because we had to try a lot of antibodies before we found a good target,” said Yokoi. “As a result, it became clear that the small and medium/large EVs are loaded with clearly different molecules. Further investigation revealed that small EVs are more suitable biomarkers than the medium and large type. We identified the membrane proteins FRα, Claudin-3, and TACSTD2 in the small EVs associated with HGSC.”

Now that the group had identified the proteins, they investigated whether they could capture EVs in a way that would allow for the identification of the presence of cancer. To do this, they turned to nanowire specialist Takao Yasui of the Graduate School of Engineering at Nagoya University who combined his research with that of Dr. Inokuma at the Japan Science and Technology Agency to create polyketone chain-coated nanowires (pNWs). This technology was ideal for separating exosomes from blood samples.

“pNW creation was tough,” Yokoi said. “We must have tried 3-4 different coatings on the nanowires. Although polyketones are a completely new material to use to coat this type of nanowire, in the end, they were such a good fit.”

“Our findings showed that each of the three identified proteins is useful as a biomarker for HGSCs,” said Yokoi. “The results of this research suggest that these diagnostic biomarkers can be used as predictive markers for specific therapies. Our results allow doctors to optimize their therapeutic strategy for ovarian cancer, therefore, they may be useful for realizing personalized medicine.”