Some skin cancers may start in hair follicles

Recent study has shown that some skin cancers start in stem cells that lend colour to hair and originate in hair follicles.

Some of the most deadly skin cancers may start in stem cells that lend colour to hair, and originate in hair follicles rather than in skin layers, a new study finds. A new study, published online in Nature Communications, found that unlike their normal counterparts, newly cancerous pigment stem cells then migrate up and out of the follicles to establish melanomas in nearby surface skin before spreading deeper. The study was conducted in genetically engineered mice, with the results confirmed in human tissue samples.

Hair follicles are complex organs that reside within skin layers. It is there that immature pigment-making cells develop cancer-causing genetic changes – and in a second step – are exposed to normal hair growth signals, say the authors of this study. Sunlight was a major risk factor for melanoma, but the triggers are always there in normal follicles.

The study results reflect development, in which human starts as a single stem cell, the embryo, and becomes a fetus made up of hundreds of cell types. Along the way, stem cells divide, multiply and specialise, until finally, they become cells capable of playing a single role.

Complicating matters, stem cells can become more than one cell type, and can shift between them. This flexibility is useful during development, but can be dangerous in adults, in whom cancer cells are thought to re acquire aspects of early embryonic cells. Because of this malleability, researchers have theorized that melanomas might arise from several stem cell types, making them hard to treat and their origin difficult to track.

The new study addresses the stem cells that mature into melanocytes,cells that make the protein pigment melanin, which protects skin by absorbing some of the sun’s ultraviolet rays. By absorbing some wavelengths of visible light, but reflecting others, pigments “create ” hair color.

The research team established a new mouse model for the study of melanoma, one engineered such that the team could edit genes in follicular melanocytes stem cells. This capability enabled researchers to introduce genetic changes that made only melanocyte stem cells and their descendants destined to form melanomas glow no matter where they traveled.

Once there, the cells shed the makers and pigment that went with their follicular origins, presumably in response to local signals. They also acquired signatures similar to nerve cells and skin cells, molecular characteristics “almost exactly like ” those noted in examinations of human melanoma tissue. “Our mouse model is the first to demonstrate that follicular oncogenic melanocyte stem cells can establish melanomas, which promises to make it useful in identifying new diagnostics and treatments for melanoma,” says first study author Qi Sun, PhD.