RESUMEN
BACKGROUND: 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. OBJECTIVES: We hypothesized that the phenotypic heterogeneity of human cutaneous melanomas is related to their content of CD133+ cells. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
