Alzheimer's disease and cancer--two of the most feared diseases of our age--would seem to be opposite diseases.  Alzheimer's disease is cell death without cell growth whereas cancer is cell growth without cell death.  The notion that they are opposite diseases appears to be reinforced by the observation that those with cancer rarely develop Alzheimer's disease and those who develop Alzheimer's disease rarely develop cancer.

But strangely enough, the two diseases may share a common origin: oxidation by either hydrogen peroxide and peroxynitrite and nitration by peroxynitrite.  In Alzheimer's disease, peroxynitrite-mediate nitration prevents the activation of the phosphatidyinositol 3-kinase-Akt pathway, thus preventing the regeneration of neurons.  In cancer oxidation of Pten prevents dephosphorylation removing the brakes on the phosphatidylinositol 3-kinase-Akt growth pathway.  In both cases, DNA damage, inflammation, and the disabling of immune responses due to oxidation and nitration prevents the body (and brain) from being able to fight back.

In theory at least, compounds that limit oxidation and nitration, and partially reverse the multi-faceted damage that they do should help in the treatment of both disease.  For instance, polysaccharides, sapoinins and polyphenols in panax ginseng/Korean red ginseng reduce neuronal cell death while helping promote the regeneration of neurons in Alzheimer's disease, while contributing to the death of cells in cancer.

Improvement of Cognitive Deficit in Alzheimer’s Disease Patients by Long Term Treatment with Korean Red Ginseng

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3659550/

Ginseng consumption and risk of cancer: A meta-analysis

 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5005362/

Role of Asian Ginseng in the Prevention and Treatment of Cancer

 https://www.herbalgram.org/resources/herbclip/issues/bin_276/review44095/

 Thank You for all the wonderful information. I really appreciate the understanding of this disease. 

Éva1

Thank you very much, Éva.  Welcome here.

Another interesting cancer-Alzheimer's disease connection:

The research team also found that amyloid beta secreted by cancer cells ramps down immune responses that would otherwise recognize cancer cells as abnormal and attack them, much as they attack invading bacteria. The researchers theorize that amyloid beta shifts brain immune cells into a mode seen as infections fade and tissues begin to heal, enabling cancer cells to evade notice. In addition, the team showed that a treatment known to dramatically reduce amyloid beta levels, the beta secretase inhibitor LY2886721, decreased the size of brain melanoma metastases by about half in study mice.

https://nyulangone.org/news/skin-cancer-cells-they-spread-brain-use-alzheimers-disease-protein-sabotage-immune-defenses

The problem here, though, is probably not amyloid per se, but peroxynitrite (ONOO-) which by damaging t cells allows for tumors to escape the immune system.

Our results point to a physiological role for ONOO- as a down-modulator of immune responses and also as key mediator in cellular and tissue injury associated with chronic activation of the immune system.

Peroxynitrite scavenging during mouse T cell priming in vitro enhances persistence of primed T cells and blocks T cell TSWD (trophic signal withdrawal death).