The next time you look in the mirror and notice a white hair, don’t worry about it: it could be the price that your body has decided to pay to protect you from a tumor. This is what emerges from a study published in Nature Cell Biologywho conducted experiments on mice discovering an unexpected relationship between melanomas and gray hair.
The color is gone, the tumor is gone. The researchers decided to study in mice the effects of various DNA damages on melanocyte stem cells (McSC), which give life to cells that synthesize melanin, responsible for the pigmentation of hair and skin.
The experiments revealed a particular behavior of these McSCs when they underwent the so-called double strand breaka very serious lesion that damages the entire double helix structure of DNA. In this case the McSCs responded by stopping dividing and entering a state of senescence, deactivating and causing the mice’s fur to lose color.
A different behavior. By instead exposing the mice to two powerful carcinogens – UVB rays and DMBA, a substance often used in the laboratory to induce tumor growth – the McSCs did not enter a state of senescence as after the double-strand break, but instead continued to clone themselves. This reveals that the same population of stem cells can follow opposite fates, depleting or expanding depending on the damage suffered. «Growing hair and melanoma are not independent events, but divergent outcomes of stem cell stress responses», explains Emi Nishimura, coordinator of the research.
While underlining that the equation graying = protection against melanoma is wrong, the authors explain that the process of “deactivation” of McSCs actually represents a shield against the spread of melanoma, and that when this mechanism is circumvented the persistence of damaged melanocyte stem cells can favor the appearance of the tumor.