Fig. 2
Strategy for quantitative proteomic analysis for co-cultured MDA-MB-231 and 82T cells. MDA-MB-231 cells were labeled with medium (2H4-Lys and 13C6-Arg) or heavy (13C 156 N2-Lys and 13C 156 N4-Arg) amino acids and 82T cells were labeled with light or heavy (13C 156 N2-Lys and 13C 156 N4-Arg) amino acids. Heavy-labeled MDA-MB-231 and 82T cells were individually cultured and medium-labeled MDA-MB-231 and light 82T cells were co-cultured. Individually cultured and co-cultured cells were lysed and mixed correspondingly and followed by trypsin digestion, desalting and phosphotyrosine peptide enrichment. Enriched peptides were eluted and analyzed by liquid chromatography tandem-mass spectrometry