A recent high-throughput MS analysis of clinical tissue specimens from benign prostate hyperplasia (BPH), primary prostate cancer and castration-resistant prostate cancer (CRPC; the most advanced form of prostate cancer) shows that the expression levels of some enzymes of the Krebs’ cycle, including aconitase-2 and oxoglutarate dehydrogenase, are increased in primary cancer versus BPH but decreased during transition from primary, untreated cancer to CRPC. The gene discussed is ACO2; the disease is prostate cancer.