Secretory proteins are a potential source of biomarkers of disease, as such proteins are involved in intercellular communication and cell adhesion, and have the potential to enter the circulation. As a result, these proteins are candidates as markers of cancer and tumor progression, and their study may help in obtaining novel diagnostic and prognostic tools. Previous secreted protein reports have shown poor secreted proteome enrichment, with samples often dominated by cytosolic proteins present in the culture media. A method has been developed which provides a highly enriched secreted proteome and the approach has been tested on three different cancer cell lines. The method is based on the optimization of cell incubation conditions in protein-free medium, and the secreted proteins are concentrated and fractionated using a reverse phase tC2 Sorbent, followed by peptide mass fingerprinting for protein identification. An average of 88 proteins were identified in each cancer cell line, of which more than 76% are known to be secreted, possess a signal peptide or a transmembrane domain. Given the importance of secreted proteins as a source for early detection and diagnosis of disease, this approach may help to discover novel candidate biomarkers with potential clinical significance.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]