CD133+ cell content correlates with tumour growth in melanomas from skin with chronic sun-induced damage

Melanoma is responsible for almost 80% of the deaths attributed to skin cancer. Stem cells, defined by CD133 expression, have been implicated in melanoma tumour growth, but their specific role is still uncertain.We hypothesized that the phenotypic heterogeneity of human cutaneous melanomas is related to their content of CD133+ cells.We compared the percentages of CD133+ cells in 29 tumours from four classic types of melanoma: lentigo maligna melanoma (LMM), superficial spreading melanoma, nodular melanoma and acral lentiginous melanoma (ALM). Also, we compared the percentages of CD133+ cells in melanomas with different degrees of exposure to ultraviolet radiation: 16 melanomas from skin with chronic sun-induced damage and 13 melanomas from skin without such damage.We found a statistically significant increase of CD133+ cells in three different contexts: in melanomas arising on skin with signs of chronic sun-induced damage vs. nonexposed skin, in melanomas in situ vs. invasive melanomas, and in LMM vs. ALM. The proportions of CD133+ cells did not differ among samples of normal skin with different degrees of sun exposure. A distinct subpopulation of CD133+CXCR4+ cancer stem cells (CSCs) was identified and shown to be related to the invasive phenotype of the tumours.Here, we provide evidence showing, for the first time, that an increase in the CD133+ cell content is associated both with melanomas arising on skin with signs of chronic sun-induced damage and in melanomas in situ with better prognosis. Moreover, our study further confirms the existence of a subpopulation of CD133+CXCR4+ CSCs in cutaneous melanomas with invasive phenotype and poor prognosis.