ALDH2 and breast cancer: 2DE and MALDI-TOF MS were employed to detect differences in serum protein expression between patients with male BC (MBC) and healthy controls, emphasizing proteins involved in mitochondrial function (i.e., mitochondrial aldehyde dehydrogenase (ALDH2)), cell cycle regulation (cell division cycle 7-related protein kinase (CDC7)), lipid metabolism and transport (apolipoproteins APOA1 and APOE), apoptosis and immune response (clusterin (CLUS), CD5L, and CCL14), transcription (STAT3 and SSX3), invasion and metastasis, estrogen synthesis, and other biological processes [204].