KLK6 and early-onset autosomal dominant Alzheimer disease: Kallikrein-related peptidase 6 (KLK6) was initially identified by three different groups who named it protease M in breast cancer (Anisowicz et al, 1996), zyme in Alzheimer's disease (Little et al, 1997), and neurosin in colon adenocarcinoma (Yamashiro et al, 1997).