Scientists at Tokyo Medical and Dental University, led by Dr. Emi K. Nishimura, have discovered a connection between gray hair formation and one of the deadliest forms of skin cancer — melanoma. The groundbreaking study was published on October 6 in Nature Cell Biology.
The research revealed that pigment-producing stem cells in hair follicles react to stress in two dramatically different ways: some die off, leading to gray hair, while others survive and proliferate — a process that can potentially trigger melanoma.
Using mouse models and human tissue samples, the team studied melanocyte stem cells, which are responsible for producing pigment in both hair and skin. When exposed to stressors that damage DNA, such as chemicals simulating UV exposure, the scientists observed two distinct outcomes.
Under normal conditions, damaged cells stop renewing themselves and transform into mature pigment cells that eventually die — causing hair to lose its color. However, when the surrounding tissue environment was altered to encourage cell survival, those same damaged stem cells continued dividing, accumulating mutations and beginning to behave like cancer cells.
Further experiments showed that cellular signals, including the growth-promoting molecule KIT ligand, influenced how these cells moved and reacted to stress. This suggests that whether a cell dies harmlessly or becomes cancerous depends on environmental cues from nearby tissues.
Dr. Nishimura explained that the findings reframe hair graying and melanoma as two possible outcomes of the same biological process — the way stem cells respond to damage and stress. Her team identified this as a biological trade-off between aging and cancer.
The researchers emphasized that gray hair does not protect against cancer. Instead, graying may reflect the body’s natural defense mechanism, in which damaged pigment cells are eliminated before they can turn malignant. If this mechanism fails and damaged cells survive, the risk of melanoma increases.
Although the study was conducted on mice, it offers valuable insights into how aging processes may protect humans from cancer, and why some individuals develop melanoma without clear warning signs.
According to the research team, the findings underscore the body’s delicate balance between cellular aging and cancer prevention, where even small disruptions can determine whether a person experiences a harmless sign of aging — or a potentially deadly disease.
