the Unexpected Link Between Gray Hair and Cancer prevention
Scientists at The University of Tokyo have uncovered a surprising connection between the process of hair graying and the body’s defense against melanoma, the most dangerous form of skin cancer.Published in Nature Cell Biology in October 2025,the research,led by Professor Emi Nishimura and Assistant Professor Yasuaki Mohri,reveals that hair turning gray isn’t simply a cosmetic effect of aging,but a perhaps protective mechanism triggered by DNA damage in melanocyte stem cells (McSCs).
These McSCs, located in the bulge-sub-bulge area of hair follicles, are responsible for replenishing melanocytes – the cells that give hair and skin their color. The study demonstrates that when McSCs experience DNA double-strand breaks, they enter a state called senescence-coupled differentiation (seno-differentiation). This process causes the stem cells to permanently mature and eventually be lost, resulting in a loss of pigment and, consequently, gray hair. Crucially, this process is regulated by the activation of the p53-p21 signaling pathway.
However, the researchers found that not all DNA damage leads to graying. Exposure to certain carcinogens,like 7,12-dimethylbenz(a)anthracene and ultraviolet B radiation,prompts a different response. Instead of undergoing seno-differentiation, these damaged McSCs avoid maturation and continue to divide, expanding their population. This expansion is fueled by signals from surrounding tissues, specifically KIT ligand released from the epidermis. These signals effectively block the protective differentiation response, potentially increasing the risk of melanoma.
“These findings reveal that the same stem cell population can follow antagonistic fates – exhaustion or expansion – depending on the type of stress and microenvironmental signals,” explains Professor Nishimura. The research reframes hair graying and melanoma as divergent outcomes of how stem cells respond to stress, rather than unrelated phenomena.
Importantly, the study does not suggest that gray hair prevents cancer. Instead, seno-differentiation appears to be a natural defense mechanism, eliminating damaged stem cells before they can become cancerous. When this safeguard is bypassed, damaged cells can survive and potentially develop into melanoma.
The findings highlight the importance of “senolysis,” the natural removal of compromised stem cells, as a preventative measure against cancer. By identifying the molecular pathways governing these opposing cellular fates, the research connects the biology of aging with cancer progress, offering new insights into how the body manages cellular stress and maintains tissue health.
The research was supported by multiple grants from the Japan Society for the Promotion of Science (JSPS) and the Japan Agency for Medical Research and Development (AMED), including grants focused on scientific research, aging, longevity, and vaccine development.