Grey hair and cancer: Greying hair may reflect the body’s attempt to prevent cancer, according to new mouse research that links loss of hair pigment to a protective response against DNA damage in stem cells.
Scientists focused on melanocyte stem cells, which reside in hair follicles and replenish pigment-producing melanocytes that give hair its colour. The team found that when these stem cells sustained DNA double-strand breaks, damage that can arise from everyday sources such as ultraviolet radiation or normal metabolism, they underwent an irreversible maturation process dubbed “seno-differentiation.”
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By exiting the stem-cell pool and turning into short-lived pigment cells, they were effectively removed from circulation, reducing the chance that damaged cells could accumulate mutations and seed cancers. The visible consequence was greying hair.
The study also showed that this protective route is context-dependent. In experiments exposing mice to cancer-promoting signals, such as carcinogenic chemicals or ultraviolet radiation, melanocyte stem cells sometimes bypassed seno-differentiation and instead continued self-renewing despite genetic damage. That persistence created conditions favourable for melanoma to arise. The findings suggest the same stem-cell population can take “antagonistic” paths: either differentiating and disappearing, which contributes to greying, or continuing to divide and increasing cancer risk.
Researchers say the work reframes greying and melanoma as related outcomes of the body’s balancing act between tissue renewal and tumour suppression. Greying itself is not a shield against cancer; rather, it may be a by-product of a safeguard that culls risky cells from the stem-cell reservoir. When that control falters or is overridden, malignancy may follow.
The authors cautioned that the evidence comes primarily from mouse models, and it remains to be seen whether human melanocyte stem cells behave the same way.
