Immune cells can use ketone bodies as an alternative energy source in the absence of glucose; however, some tumor cells, such as glioblastoma (GBM), are classified as "glycolysis subtype" for the lack of ketone body oxidases, such as 3-hydroxybutyrate dehydrogenase (BDH1) or 3-succinyl-CoA transferase (OXCT1), because of genetic mutations or mitochondrial damage 31. The gene discussed is OXCT1; the disease is glioblastoma.