EGFR mediates stabilities of a wide spectrum of proteins. Treatment of the cells with EGFR tyrosine kinase inhibitors (EGFR-TKIs) leads to degradation of these proteins. To define the proteins and corresponding pathways of EGFR-stabilized proteins, we use mass spectrum to quantify the protein levels in the untreated control HCC827 cells and the cells treated with erlotinib or gefitinib.