From the article:
Thanks to those data, which showed participants with cancer had fewer hallmarks of Alzheimer’s disease in their brains as well as a reduced likelihood of neurodegenerative symptoms during their lifetimes, lead study author Erin Abner, a University of Kentucky epidemiologist and aging researcher and her team were able to offer the clearest picture yet of a molecular mechanism that seems to link the two diseases.
“The connection is becoming more and more apparent,” New York University cancer researcher Eva Hernando-Monge, who didn’t work on the study, tells The Scientist.
They investigated cancer deaths for traces of Alzheimer’s:
As cohort members passed away, the team autopsied their brains to look for biomarkers associated with Alzheimer’s disease, including structures such as neurofibrillary tangles and neuritic plaques. They also noted when someone carried the APOE ε4 allele, a known genetic risk factor for the neurodegenerative condition.
[…]
The analysis revealed “less Alzheimer’s pathology in the people who had cancer, both amyloid and tau,” Abner says. “We also saw evidence [that] another amyloid pathology—cerebral amyloid angiopathy, which is amyloid aggregation in blood vessel walls—was lower.
Mechanisms of the cancer-Alzheimer’s anti-relationship:
Processes related to cell growth and survival, as well as the production of specific molecules including the antistress response protein vimentin and the enzyme carbonic anhydrase, are all upregulated in cancer, he finds. Alzheimer’s occurs when these processes and proteins are downregulated.
Another review, published in Molecular Psychiatry in 2021, identifies the proteins p53 and PIN1 as implicated in both cancer and Alzheimer’s. PIN1 overexpression is associated with myriad cancers, but its absence is linked to the formation of the Alzheimer’s biomarkers tracked in the Brain study. Meanwhile, p53 has a well-established anticancer role, but can also contribute to neurodegenerative disease.