There is inverse relationship between Cancer and Alzheimer’s disease in aspects such as P53, estrogen, neurotrophins and growth factors, growth and proliferation, cAMP, EGFR, Bcl-2, apoptosis pathways, IGF-1, HSV, TDP-43, Alzheimer’s risk decreases from apoE4 to E3 to E2 but growth and survival improves respectively, notch signals and presenilins, NCAM, TNF alpha, PI3K/AKT/MTOR pathway, telomerase, ROS, ACE levels. This evidence concerns the gene NCAM1 and early-onset autosomal dominant Alzheimer disease.