RESUMEN
Mass spectrometry-based quantitative proteomics has become an indispensable tool for tumor marker discovery.Stable isotope labeling with amino acid in cell culture(SILAC),as a representative of in vivo metabolic labeling strategy,is a simple and relatively quantitative assay for comparative proteomics.Two kinds of cultured cells are grown in the medium containing either a light or heavy isotope labeled essential amino acids.After several cell doublings,the heavy amino acids are introduced into the nascent polypeptides in a sequence-specific fashion and the natural amino acid is completely replaced by its isotopically labeled analog.Accuracy quantification would be feasible by analyzing the peak intensities of every same peptide pairs labeled with light or heavy isotopes by the mass spectrometry.Compared with chemical labeling,SILAC requires much less amount of labeled proteins,and it is an efficient,straightforward,reproducible and accurate approach in cell-based systems.This method can not only investigate the dynamics of protein abundance,but also monitor the variation of posttranslational modifications and protein-protein interactions qualitatively and quantitatively.It is a powerful and important quantitative proteomics tool for tumor marker discovery.