CST3 and Alzheimer disease: Cystatin C (CST3) is highly expressed in mature human astrocytes (Bachoo et al, 2004; Zhang et al, 2016) and is induced in Alzheimer's disease and epilepsy (Steinhoff et al, 2001; Pirttilä et al, 2005; Gauthier et al, 2011), raising the possibility that astrocyte‐like glioma cells may be responding to the same cues or stresses that reactive astrocytes encounter in these disorders.