C9 and cancer: It is worth mentioning that, out of the five potential plasma cancer biomarkers identified using a very different methodology (profiling of plasma proteome with monoclonal antibody libraries) [36], four proteins (alpha-1-antichymotrypsin, haptoglobin, complement C9, and leucine-rich α-2 glycoprotein precursor) were also identified using 2D-DIGE studies.