A study conducted on mice suggests a surprising link between cancer and Alzheimer’s disease: tumors may secrete a protein that helps clear amyloid plaques in the brain, a hallmark of the debilitating neurological condition. The research, published February 18, 2026, indicates that cystatin-C, a protein released by tumor cells, crosses the blood-brain barrier and stimulates microglia – the brain’s immune cells – to remove the plaques.
Researchers implanted human lung, prostate and colon tumors under the skin of mice genetically predisposed to develop Alzheimer’s-like amyloid plaques. Contrary to expectations, the mice with tumors exhibited significantly reduced amyloid plaque accumulation compared to those without tumors. In some instances, the animals also demonstrated improved cognitive function, suggesting a direct correlation between tumor presence and plaque reduction, according to a report in The Conversation.
The protective effect appears to be mediated by cystatin-C. Once in the brain, the protein binds to amyloid oligomers, triggering a response in microglia. Specifically, cystatin-C activates a receptor on microglia called TREM2, enhancing their ability to clear existing amyloid plaques, as detailed in research published by Nature, and Archyde.com.
This finding builds on epidemiological observations that individuals with a history of cancer have a lower risk of developing Alzheimer’s disease. While the relationship between the two conditions has long been recognized, the underlying mechanisms remained unclear until now. The study offers a potential explanation for this inverse correlation, suggesting that cancer may inadvertently trigger a protective response in the brain.
The research, however, is still in its early stages and was conducted on mice. Further investigation is needed to determine whether similar mechanisms operate in humans and whether cystatin-C or TREM2 activation could be harnessed as a therapeutic strategy for Alzheimer’s disease. Researchers note that the study opens “interesting avenues for translational clinical studies,” but cautions that the complexities of human physiology may differ significantly from those observed in mice.
The study does not address the type or stage of cancer that might be most effective in triggering this protective response, nor does it explore potential side effects of artificially introducing cystatin-C into the brain. The team is currently working to further elucidate the signaling pathways involved and to identify potential drug candidates that could mimic the effects of cystatin-C without the need for tumor implantation.
