At first glance, Alzheimer's disease and cancer seem like entirely different illnesses. Alzheimer's gradually harms the brain and memory, while cancer is associated with rapid, uncontrolled cell growth throughout the body. However, researchers at the MUSC Hollings Cancer Center in the US have found an interesting connection between the two.

The study published in Cancer Research, revealed that a protein strongly linked to Alzheimer's might actually boost the immune system's ability to fight cancer, ageing, and even other brain diseases.

The Alzheimer's–Cancer Mystery

For years, scientists have studied an interesting pattern: people with Alzheimer's are significantly less likely to develop cancer. To find an explanation behind this link, Dr Besim Ogretmen, Dr Kalyani Sonawane, and their team analyzed five years of national health data. The result was surprising: individuals over 59 with Alzheimer's were 21 times less likely to develop cancer compared to those without the condition. The numbers were clear, but the reason behind this unexpected connection remained unclear.

One Protein, Two Very Different Roles

The scientists traced the connection to a protein called amyloid beta. This protein is famous for its harmful role in Alzheimer's, where it accumulates in the brain and forms damaging plaques. However, outside the brain, amyloid beta may have a different effect.

In the brain, amyloid beta blocks a process called mitophagy, which clears out damaged mitochondria. When mitophagy is blocked in brain cells, damaged mitochondria build up, leading to cell damage, memory loss, and cognitive decline.

However, in T-cells, the immune cells that fight infections and cancer, the effect is different. When amyloid beta interferes with mitophagy in these cells, it helps them by keeping more mitochondria active. This gives T-cells more energy, improving their ability to detect and attack tumours.

The same protein that harms brain cells in Alzheimer's helps T-cells become strong cancer fighters.

Making Old Immune Cells Young Again

To explore this idea further, the scientists conducted an unusual experiment. They took mitochondria from the T-cells of Alzheimer's patients and transplanted them into ageing T-cells from people without Alzheimer's.

The older immune cells began behaving like younger, more energetic ones. They regained their strength and ability to fight.

A Small Molecule With a Big Impact

The team also identified another key factor in this process, a molecule called fumarate. It helps regulate mitophagy. When fumarate levels are low, cells destroy too many mitochondria, leaving them weak and low on energy.

In cancer and ageing, this can be a serious issue. So, the researchers tested adding fumarate back into ageing T-cells. Mitophagy slowed down, more mitochondria were preserved, and the immune cells received a powerful energy boost. This finding suggests that fumarate supplements or drugs might help support immune health, especially in older adults or cancer patients.

Cancer and Ageing Treatments

Together, these findings could explain why people with Alzheimer's are less likely to develop cancer and point to exciting new ways to improve health. Rather than directly targeting cancer, this research focuses on strengthening the immune system. By restoring energy to T-cells, scientists could make current treatments like immunotherapy more effective, especially for older patients.

Dr Ogretmen says this discovery is a great example of how research in one field can lead to breakthroughs in another.

While more research is needed, this study could mark the beginning of a whole new way to think about cancer, ageing, and the immune system.

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