Masakazu Toi

Lipids are a major component of extracellular vesicles; however, their significance in tumorigenesis and progression has not been well elucidated. As we previously found that lipid profiles drastically changed in breast tumors upon progression, we hypothesized that lipid profiles of plasma‐derived extracellular vesicles could be utilized as breast cancer biomarkers. Here, we adopted modified sucrose cushion ultracentrifugation to isolate plasma‐derived extracellular vesicles from breast cancer ( n = 105), benign ( n = 11), and healthy individuals ( n = 43) in two independent cohorts ( n = 126 and n = 33) and conducted targeted lipidomic analysis. We established a breast cancer diagnostic model comprising three lipids that showed favorable performance with the area under the receiver operating characteristic curve of 0.759, 0.743, and 0.804 in the training, internal validation, and external test sets, respectively. Moreover, we identified several lipids that could effectively discriminate breast cancer progression and subtypes: phosphatidylethanolamines and phosphatidylserines were relatively higher in Stage III, whereas phosphatidylcholines and sphingomyelins were higher in Stage IV; phosphatidylcholines and ceramides were correspondingly concentrated in HER2‐positive patients, while lysophosphatidylcholines and polyunsaturated triglycerides were concentrated in the triple‐negative breast cancer subtype. Lipid profiling of plasma‐derived extracellular vesicles is a non‐invasive and promising approach for diagnosing, staging, and subtyping breast cancer.