MAPT and Alzheimer disease: Consistent with the Aβ results, PHF-tau was increased by the overexpression of mutant APP and was highly promoted by the co-expression of mutant PSEN1. In addition, the expression of NFT-like structures was strongly enhanced by the overexpression of mutant APP and PSEN1. In addition, AD CO showed a marked increase in the cellular apoptotic marker, cCASP3.