Figure 1.

Schematic of the protein extraction procedure from a human GBM xenografted in a GFP-expressing immunodeficient mouse. Since the excision of the human tumor tissue (in blue) includes a variable proportion of mouse cells (in green), the surrogate peptide selection process of a given protein A must exclusively consider the human specific peptide (blue peptides). Monitoring protein A via human specific peptides in different tumor pieces will eliminate the bias induced by the presence of mouse proteins within the samples.