A previous proteomic study used MALDI-TOF/TOF MS in total extracts from seven pairs of colorectal cancer tissues and their adjacent normal mucosa and revealed significant changes in the expression of mitochondrial enzymes participating to the Krebs’ cycle, with a 3- to 5-fold increase in the levels of malate dehydrogenase and a 6-fold decrease in the levels of aconitase 2 and aconitate hydratase [125], providing evidence for alteration of metabolic pathways in colorectal tumorigenesis, and highlighting the potential of mitochondrial proteins as diagnostic biomarkers in colorectal cancer. The gene discussed is PHGDH; the disease is colorectal cancer.