Elevated expression of complement C3 protein in chemically induced hepatotumorogenesis in Wistar rats: a correlative proteomics and histopathological study.

Liver cancer remains the leading cause of cancer-related mortality worldwide. Early detection of liver cancer is problematic due to the lack of a marker with high diagnosis sensitivity and specificity. The present study was designed to determine the differently expressed proteins at early stage in the serum of animals with liver cancer vis-à-vis controls and figure out the function of the proteins. One-dimensional electrophoresis (1D), two-dimensional electrophoresis (2DE) and liquid chromatography mass spectrometry (LC-MS/MS) were used to screen the serum proteins of liver cancer induced in animals by diethyl nitrosamine (DEN)+2-acetyl amino fluorine (2-AAF). From optimized 2DE image and computer assisted PD Quest analysis were found to be differentially expressed spots when the serum from normal and treated animals were compared. Among these, one spot was selected whose expression level was higher in DEN+2-AAF treated animal sera than in adjacent normal animal sera. The target spot was excised from the 2D gel of liver cancer sera and the peptide mass fingerprinting as obtained LC-MS/MS analysis after digesting the chosen protein spot. This was identified to be complement C3 protein. The changes in complement C3 expression level were validated by Western blot analysis. We reported that the changes in complement C3 concentration start at very early stage of tumorogenesis. The fully grown tumors were developed at 120 days and hepatotumorogenesis was confirmed by histopathological examination. This protein may therefore represent a powerful tool in search for candidate biomarkers for HCC.