To determine the absolute copy number of proteins in MDA-MB231 breast cancer cells, we employed IBAQ mediated absolute quantification of proteins based on (Schwanhäusser et al., Nature, 2011), with some modifications. Maqquant calculated iBAQ values were calibrated using spike-in standards, and used to calculate copy numbers for each identified protein within the dataset. Copy numbers for a total of 3,584 proteins were calculated in MDA-MB231 cells.