Researchers at Tokyo Medical and Dental University, led by Dr. Emi K. Nishimura, identified how grey hair growth is connected to one of the deadliest forms of skin cancer. The findings were published Oct. 6 in the journal Nature Cell Biology.
The study found that pigment-producing stem cells in hair follicles respond to stress in dramatically different ways.
Cells in certain environments may either perish, resulting in gray hair, or proliferate, potentially leading to melanoma, as stated in a university press release.
The researchers examined melanocyte stem cells, the cells that give hair and skin their color, using mouse models and tissue samples. In revealing these cells to forms of stress that damage DNA — such as chemicals that mimic UV exposure — the scientists observed how the cells behaved inside their natural setting.
Graying occurs when cells, in response to damage, cease their self-renewal and transform into mature pigment cells that subsequently die. This process deprives the hair of its color source.
But when the researchers changed the surrounding tissue to stimulate cell survival, the damaged stem cells began dividing again instead of shutting down. Those surviving cells accumulated more genetic damage and, in some cases, started behaving like ‘cancer cells.’
Further experiments revealed that signals from the cellular environment, such as the cell growth-promoting molecule KIT ligand, influenced the cells’ directional movement.
This indicates that the fate of a cell, whether it harmlessly disappears or develops into melanoma, is determined by the cues it receives from surrounding tissues.
Nishimura said in the release that it reframes hair graying and melanoma not as irrelevant events, but as divergent outcomes of stem cell stress responses.
Nishimura’s team has identified a biological trade-off between aging and cancer.
However, this does not imply that gray hair prevents cancer. Instead, researchers suggest that when pigment cells cease to divide and subsequently die off, it represents the body’s mechanism for eliminating damaged cells. Should this process fail and damaged cells persist, they could potentially lead to cancer.
The study was performed on mice, but its implications could help scientists understand why some people develop melanoma without obvious warning signs, and how the natural mechanisms of aging could actually protect against cancer.
According to the researchers, the discovery shows how well balanced the body’s cellular responses are and how tiny changes in that balance can mean the difference between a harmless sign of aging and a life-threatening disease.