Serum Exosomes Expressing CD9, CD63 and HER2 From Breast-Cancer Patients Decreased After Surgery of the Primary Tumor: A Potential Biomarker of Tumor Burden.

BACKGROUND/AIM: Exosomes are extracellular vesicles produced by both normal and cancer cells. Previous research has demonstrated that circulating exosomes derived from cancer cells may create a niche for future metastasis, distant from the primary tumor. In the present report, circulating exosomes were captured and quantified based on exosome-surface proteins in pre- and post-operative serum of breast cancer patients, focusing on the exosome markers CD9 and CD63, as well as HER2, a therapeutic target for breast cancer.

MATERIALS AND METHODS

Eight breast cancer patients were recruited, and their pre- and post-operative serum samples were analyzed for CD63 and CD9; or CD9 and human epidermal growth factor receptor-2 (HER2), double-positive exosomes. An ExoCounter with antibody-conjugated beads was used to capture serum-derived exosomes. Sera from patients with tumors larger than 10 mm were used for analysis. The resected breast cancer was also histopathologically analyzed for the presence of HER2.

RESULTS

CD63 and CD9 double-positive serum exosomes and CD9 and HER2 double-positive serum exosomes decreased after surgery in breast-cancer patients whose tumors expressed HER2, as determined by histopathological analysis.

CONCLUSION

Serum exosomes expressing CD9, CD63 and HER2 are candidate biomarkers of tumor burden in HER2-positive breast-cancer patients.