A recent study from the University of Tokyo indicates that graying hair may serve as a built-in safeguard against melanoma, the deadliest form of skin cancer.
Researchers discovered that the stem cells responsible for hair pigmentation make a critical decision after DNA damage: they can either mature into pigment-producing cells, ultimately depleting their numbers and causing gray hair, or remain persistent and risk becoming cancerous.
The work, led by Professor Emi Nishimura and Assistant Professor Yasuaki Mohri, shows that the outcome depends on the type of damage and chemical signals from surrounding tissue.
When melanocyte stem cells in mice suffered severe genomic injury, such as double-strand DNA breaks, they triggered a protective response called senescence-coupled differentiation via the p53–p21 pathway. The damaged stem cells stopped renewing themselves, differentiated into pigment cells, and were eventually lost, resulting in gray hair but eliminating the cancer threat.
Exposure to carcinogens such as UVB light or the chemical DMBA altered that response. Instead of disappearing, the damaged stem cells activated a survival pathway involving arachidonic acid metabolism and the release of higher levels of KIT ligand (KITL) by nearby skin cells. The cells continued dividing and preserved hair color, but became far more likely to develop into melanoma.
Live imaging of mouse hair follicles confirmed the shift. Radiation that normally caused rapid stem-cell loss and premature graying had little effect when carcinogens were present.
“The same stem cell population can follow antagonistic fates — exhaustion or expansion — depending on the type of stress and microenvironmental signals,” Nishimura said, Brighter Side reported.
The findings, published in a recent issue of the scientific journal Nature, reframe graying as an active anti-cancer mechanism rather than simple deterioration.
Scientists caution that the link is not a direct cause-and-effect. Hair color itself does not determine cancer risk; rather, the body’s decision to sacrifice pigment stem cells appears to reduce the pool of cells that could turn malignant.
The discovery highlights a delicate balance: attempts to reverse gray hair by keeping melanocyte stem cells active longer might unintentionally raise melanoma risk, while strategies that promote controlled stem-cell loss could offer new ways to prevent skin cancer.
The Tokyo team says the results could eventually lead to therapies that safely slow visible skin and hair aging or improve melanoma prevention by precisely tuning how stem cells respond to damage.