Two recent studies suggest that aberrant NADPH production is associated with 5-ALA-induced fluorescence in glioma cells.66,67 NADPH is generated during the formation of α-ketoglutarate, feeding into the TCA cycle by isocitrate dehydrogenases (IDH1 and IDH2) and glutaminases (GLS and GLS2). The gene discussed is GLS2; the disease is central nervous system cancer.