Amyloid precursor protein (APP) is involved in the accumulation of 
alpha-synuclein, the main component of Lewy bodies. It is currently unknown, 
however, whether any of the APP isoforms is instrumental in alpha-synuclein 
deposition in dementia with Lewy bodies (DLB). Using real-time RT-PCR, we have 
studied relative mRNA expression levels of APP isoforms in frozen postmortem 
frontal cortices of DLB patients, Alzheimer disease (AD) patients, and control 
subjects. Of the three main APP isoforms, the two with a Kunitz protease 
inhibitory (KPI) motif (APP770 and APP751) were found to be specifically 
overexpressed in the frontal cortices of DLB patients when compared with 
controls and AD patients. These findings suggest a specific role of APP isoforms 
containing Kunitz protease inhibitor in DLB pathogenesis.