Pesquisadores from Universidade from Ciência and Tecnologia Huazhong from China have identified a molecular mechanism that explains why cancer and Alzheimer rarely coexist in the same patient. A study published in January 2026 in the journal Cell demonstrated that tumor cells produce a protein called cystatin C, which circulates in the blood, crosses the blood-brain barrier and significantly reduces protein deposits associated with dementia. Tests on mice modified to develop characteristics of Alzheimer showed a clear reduction in brain plaques and an improvement in the cognitive performance of animals that received the protein.
Cistatina C activates brain defense against amyloid plaques
Cystatin C is released by cancer cells and travels through the bloodstream to the brain. Once in brain tissue, the molecule binds to beta-amyloid oligomers, small protein clusters that form the toxic plaques characteristic of Alzheimer. Essa binding activates the TREM2 receptor on microglia cells, which functions as the brain’s immune system.
Quando activated by the cystatin C pathway, microglia begin to degrade the plaques already formed. The process not only prevents the formation of new deposits but also removes existing ones. The researchers confirmed the importance of this pathway by blocking cystatin C experimentally: the protective effect disappeared and the plaques began to accumulate again.
Consistent Resultados across multiple tumor types
- Tumores from human lung, prostate and colon were transplanted into mice with a genetic predisposition to Alzheimer.
- Todos cancer types tested produced significant reduction of amyloid plaques in brain tissue.
- Cystatin C was identified as the only consistently elevated secreted protein associated with protection.
- Behavioral Testes showed improvement in spatial memory, associative learning and object recognition.
- The reduction of plaques was confirmed by imaging techniques and biochemical analyzes of brain tissue.
The mice with cancer had a much lower burden of amyloid plaques in the brain compared to the control group. The difference appeared both in the quantity and distribution of deposits. The researchers followed the animals for prolonged periods, measuring protein levels in the blood and brain tissue, confirming that the mice with tumors maintained better cognitive function over time.
Isolated Proteína reproduces protective effect without the need for tumors
Após Identify cystatin C as the key factor, the team administered the purified protein directly into mice with Alzheimer. The results were consistent with those obtained in animals with transplanted tumors. Houve reduces plaques and improves cognitive tests without the need to induce cancers, eliminating the risks associated with malignant disease.
Essa approach opens perspectives for the development of future therapies. The researchers plan to test variations of the molecule and different doses. Eles also want to understand whether cystatin C affects other proteins involved in Alzheimer, such as tau, which forms tangles inside neurons. The protein’s ability to naturally cross the blood-brain barrier makes it particularly interesting for drug development.
Epidemiological Observação gains molecular basis in laboratory
The inverse correlation between cancer and Alzheimer has been known since the 2000s, when meta-analyses with millions of patients showed a reduction of around 11% in the risk of Alzheimer among those diagnosed with cancer. The new study offers a concrete mechanism to explain this long-observed epidemiological phenomenon. The discovery gains relevance because it directs attention to the role of microglia and the TREM2 receptor, whose mutation is already known as a risk factor for Alzheimer.
Especialistas consider the finding significant because it suggests that activating TREM2 in a controlled manner could become a therapeutic strategy. Microglia in brains with Alzheimer are often in a dysfunctional state, losing the ability to clear protein waste. Cystatin C appears to restore part of this function by specifically activating the receptor.
Próximos steps include human studies and advanced models
The authors emphasize that the data is limited to animal models and that translation to humans will require careful clinical studies. Diferenças in metabolism, immune response and disease progression across species need to be considered. The researchers plan to investigate whether elevated cystatin C levels in humans with a history of cancer correlate with lower imaging-detectable brain plaque burden.
Próximos team’s steps include testing cystatin C in more advanced models of Alzheimer that also include tau pathology. Eles also intends to evaluate possible long-term side effects of increasing the protein and whether it can be used preventively or in the early stages of the disease. Alzheimer disease affects millions of people around the world, and there is still no treatment that definitively stops plaque accumulation and neuronal death, making any clue about factors that naturally reduce protein deposits of great interest to the scientific community.