They conducted proteomic analyses of breast cancer cells isolated from a stage IV breast cancer patient before and after metastatic spread to the brain in athymic mice and observed a marked increase in the expression of proteins involved not only in glycolysis but also in the tricarboxylic acid cycle, including aconitate hydratase, isocitrate dehydrogenase and mitochondrial malate dehydrogenase, and in oxidative phosphorylation, including cytochrome c oxidase subunits, NADH-ubiquinone oxidoreductases and ATP synthase chains. This evidence concerns the gene MDH2 and breast cancer.