ABSTRACT
Proteomics analysis of biofluid-derived vesicles holds enormous potential for discovering non-invasive disease markers. Obtaining vesicles of sufficient quality and quantity for profiling studies has, however, been a major problem, as samples are often replete with co-isolated material that can interfere with the identification of genuine low abundance, vesicle components. Here, we used a combination of ultracentrifugation and size-exclusion chromatography to isolate and analyse vesicles of plasma or urine origin. We describe a sample-handling workflow that gives reproducible, quality vesicle isolations sufficient for subsequent protein profiling. Using a semi-quantitative aptamer-based protein array, we identified around 1,000 proteins, of which almost 400 were present at comparable quantities in plasma versus urine vesicles. Significant differences were, however, apparent with elements like HSP90, integrin αVß5 and Contactin-1 more prevalent in urinary vesicles, while hepatocyte growth factor activator, prostate-specific antigen-antichymotrypsin complex and many others were more abundant in plasma vesicles. This was also applied to a small set of specimens collected from men with metastatic prostate cancer, highlighting several proteins with the potential to indicate treatment refractory disease. The study provides a practical platform for furthering protein profiling of vesicles in prostate cancer, and, hopefully, many other disease scenarios.
ABSTRACT
Exosomes are nanometer-sized vesicles, secreted from most cell types, with documented immune-modulatory functions. Exosomes can be purified from cultured cells but to do so effectively, requires maintenance of cells at high density in order to obtain sufficient accumulation of exosomes in the culture medium, prior to purification. Whilst high density cultures can be achieved with cells in suspension, this remains difficult with adherent cells, resulting in low quantity of exosomes for subsequent study. We have used the Integra CELLine culture system, originally designed for hybridoma cultures, to achieve a significant increase in obtainable exosomes from adherent and non-adherent tumour cells. Traditional cultures of mesothelioma cells (cultured in 75 cm(2) flasks) gave an average yield of 0.78 microg+/-0.14 microg exosome/ml of conditioned medium. The CELLine Adhere 1000 (CLAD1000) flask, housing the same cell line, increased exosome yield approximately 12 fold to 10.06 microg+/-0.97 microg/ml. The morphology, phenotype and immune function of these exosomes were compared, and found to be identical in all respects. Similarly an 8 fold increase in exosome production was obtained from NKL cells (a suspension cell line) using a CELLine 1000 (CL1000) flask. The CELLine system also incurred ~5.5 fold less cost and reduced labour for cell maintenance. This simple culture system is a cost effective, useful method for significantly increasing the quantity of exosomes available from cultured cells, without detrimental effects. This tool should prove advantageous in future studies of exosome-immune modulation in cancer and other settings.
