Cancer is more common as we get older, and it is harder to treat in older people. Most lab experiments with mice use very young animals, about the same age as a 20‑year‑old human. This makes it tough to study how cancer works in older patients.
Researchers at Fox Chase Cancer Center looked at melanoma, a type of skin cancer, in mice of different ages. They found a surprising pattern: the cancer spread the least in young mice, the most in middle‑aged mice, and then less again in very old mice.
"Most experiments use young mice with a strong immune system," explained lead scientist Mitchell Fane, PhD. "If we understand how treatments affect older bodies, we can create better care for older patients."
Immune Cells May Explain the Pattern
The team thinks a special group of immune cells called gamma‑delta T cells are important. These cells act early to stop cancer from moving around the body. Young and very old mice had more of these cells, and their tumors stayed small or did not spread.
Middle‑aged mice had fewer gamma‑delta T cells, and their melanoma moved to the lungs and liver more often. The cancer also released signals that weakened these protective cells, letting the disease spread faster.
When the scientists removed gamma‑delta T cells from young and old mice, the cancer spread a lot more. Adding drugs that blocked the cancer’s suppressive signals helped protect middle‑aged mice, but not the younger or older groups.
Why Older Mice Are Hard to Use
Working with older mice is tricky. Young mice are cheap and easy to get. To have a mouse that is middle‑aged or old, researchers must wait 18‑24 months and take extra care of them.
To solve this, Fane and colleague Yash Chabra, PhD, created an aging mouse facility at their center. The new colony makes it less costly and faster for scientists to test their ideas in older animals.
Rethinking Cancer and Age
Usually, cancer risk rises with age, but studies show a drop in new cases after people reach about 80‑85 years old. Fane’s lab wants to know why very old people get less cancer while middle‑aged people get more.
The current research suggests that changes in the immune system during aging may decide when cancer spreads the most. It also shows that using older animal models can give a clearer picture of how cancer behaves in the patients who need help the most.