Proteomics analysis of cancer exosomes using a novel modified aptamer-based array (SOMAscan™) platform

Area of Science:

• Proteomics
• Extracellular Vesicles Biology
• Cancer Biomarkers

Background:

• Exosomes are small secreted vesicles implicated in intercellular communication and disease.
• Prostate cancer exosomes are potential sources for diagnostic and prognostic biomarkers.
• Current methods for exosome protein profiling have limitations.

Purpose of the Study:

• To characterize the protein content of prostate cancer exosomes using a novel proteomics technology.
• To identify proteins enriched in exosomes compared to cell lysates.
• To discover novel exosome-associated proteins for potential biomarker applications.

Main Methods:

• Utilized a novel affinity-based proteomics technology employing SOMAmers® (slow off-rate modified aptamers).
• Purified exosomes from the Du145 prostate cancer cell line using sucrose gradient ultracentrifugation.
• Analyzed exosome and cell lysate protein profiles using the SOMAscan™ array (version 3.0).
• Validated findings using individual SOMAmer® reagents, antibodies, and Western blotting.

Main Results:

• Identified over 100 proteins enriched in exosomes relative to cells.
• Confirmed known exosomal proteins (e.g., MFG-E8, integrins, MET) and identified less common ones (e.g., ROR1, ITIH4).
• Discovered over 300 proteins with previously unknown association with prostate cancer exosomes.
• Validated enrichment of specific proteins like NOTCH-3, L1CAM, RAC1, and ADAM9.

Conclusions:

• The SOMAmer®-based assay is an effective platform for exosome proteomics.
• This study significantly expands the known protein repertoire of prostate cancer exosomes.
• The identified proteins represent potential novel biomarkers for prostate cancer detection and monitoring.