Analysis of Secreted Proteins as an in vitro Model for Discovery of Liver Toxicity Markers

Despite the wealth of sequence data and new technologies that can scan large portions of the transcriptome of proteome in a single experiment, attempts to identify human biomarkers of toxicity have met with limited success. We have adapted an in vitro model system to identify proteins secreted by a human hepatoma-derived cell line (HepG2/C3A) in response to toxicant exposure. Using quantitative proteomics, we can find alterations in the abundance of proteins at the source of damage--liver cells--that are likely to be present in blood samples of exposed animals. In a proof of concept experiment, conditioned medium from cells exposed to ethanol was subjected to quantitative mass spectral analysis after abundant proteins were immunodepleted. Eighty seven proteins were identified with almost half changing in abundance. Some of these were only identified in the highest treatment condition and presumably result from the release of intracellular proteins into the medium when the cell membrane is disrupted upon cell death. However, the majority of the identified proteins reflect known consequences of ethanol exposure or alcoholism.
Pub. in Journal of Proteome Research, v9, p5794 5802, 2010.