For further investigation, we selected one protein only identified in ovarian cancer cells (vimentin, Figure 2, spot 1, 1*), one protein only identified in colorectal cancer cells (growth receptor factor bound protein 2, Grb2, Figure 2, spot 2), and one protein identified in all four cell lines (glutathione-S-transferase π, GSTP1, Figure 2, spot 3). This evidence concerns the gene GSTP1 and colorectal cancer.