New Approaches for Biomarker Discovery: The Search for Liver Fibrosis Markers in Hepatitis C Patients

Despite many shortcomings, liver biopsy is regarded as the gold
standard for assessing liver fibrosis. A less invasive and equally
or more reliable approach would constitute a major advancement in
the field. Proteomics can aid discovery of novel serological markers
and these proteins can be measured in patient blood. A major challenge
of discovering biomarkers in serum is the presence of highly abundant
serum proteins, which restricts the levels of total protein loaded
onto gels and limits the detection of low abundance features. To overcome
this problem, we used two-dimensional gel electrophoresis (2-DE) over
a narrow pH 3−5.6 range since this lies outside the range of
highly abundant albumin, transferrin and immunoglobulins. In addition,
we used in-solution isoelectric focusing followed by SDS-PAGE to find
biomarkers in hepatitis C induced liver cirrhosis. Using the pH 3−5.6
range for 2-DE, we achieved improved representation of low abundance
features and enhanced separation. We found in-solution isoelectric
focusing to be beneficial for analyzing basic, high molecular weight
proteins. Using this method, the beta chains of both complement C3
and C4 were found to decrease in serum from hepatitis C patients with
cirrhosis, a change not observed previously by 2-DE. We present two
proteomics approaches that can aid in the discovery of clinical biomarkers
in various diseases and discuss how these approaches have helped to
identify 23 novel biomarkers for hepatic fibrosis.