CTSB and neoplasm: Hayashi et al. reported that AQP1 induction correlated with tumor cell metabolism and increased glycolysis and lactate dehydrogenase (LDH) activity, with patient GBM tissue exhibiting increased coincident AQP1, LDH, and cathepsin B expression levels which contributed to acidification of the extracellular milieu and glioma cell invasiveness (34).