Abstract

Click Chemistry-Mediated Surface Protein Assay for Quantifying Subpopulations of Hepatocellular Carcinoma-Associated Extracellular Vesicles

Yazhen Zhu, Assistant Project Scientist, David Geffen School of Medicine at UCLA

Extracellular vesicles (EVs) are a heterogeneous group of phospholipid bilayer-enclosed particles that are released by all types of cells, and even more so by tumor cells. It is well known that tumor-associated EVs are present in circulation at a relatively early stage of disease. Since the surface proteins of tumor-associated EVs mirror those of the parental tumor cells, performing surface protein analysis on tumor-associated EVs offers a systemic and repeatable assessment of tumor cells that can offer substantial diagnostic value for early-stage diseases. Hepatocellular carcinoma (HCC) predominantly occurs in patients with underlying cirrhosis, and is the fourth most common cause of cancer-related deaths worldwide. Current clinical surveillance guidelines, which include biannual liver ultrasonography with or without serum alpha-fetoprotein (AFP), exhibit low sensitivity to detect early-stage HCC, limiting delivery of curative-intent treatments. Therefore, exploiting the diagnostic potential of HCC EVs’ surface protein signatures as a novel biomarker for detecting early-stage HCC holds great promise to augment current HCC diagnostic modalities. We demonstrated the feasibility of HCC EV Surface Protein Assay (SPA) for detecting subpopulations of HCC EVs by coupling two platform technologies: Click Chemistry-mediated EV Click Beads for isolation and enrichment of HCC EVs, and real-time immuno-PCR for HCC EV quantification. The resultant HCC EV Surface Protein Scores exhibit great diagnostic potential for early detection of HCC.