Poster presentation, P134

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

The Molecular Phenotype of Acquired Melanocytic Naevi

Understanding of the pathogenesis of cutaneous melanoma remains a major challenge. The cancer stem cell hypothesis is gaining widespread recognition as it challenges the widely accepted model of cancer development. This model further opens the question of the relationship between melanocytic naevi and melanoma. To examine the hypothesis that melanocytic naevi may originate from a pluripotent or neural crest-like stem cell and not via de-differentiation from a mature epidermal melanocyte, and to characterise, in detail, the phenotype of a “naevus cell”, we are systematically re-evaluating a series of formalin-fixed, paraffin embedded naevus biopsy samples, as well as cultured naevus cells. Compound, junctional, intradermal, blue and dysplastic naevus subtypes are being analysed using combined techniques of immunofluorescence, real time PCR and protein expression analysis. Melanocyte markers Melan A (Mart-1) and S100, as well as the Schwann cell markers S100 and Protein 0 are being utilised to evaluate the phenotype of naevus cells. To determine the presence and/or contribution of pluripotent or precursor cells within naevus tissue, we are using antibodies to pluripotency markers OCT 4 and NANOG; and to neural crest precursor marker NGFR P75. Lastly, to determine the presence and/or location of possible proliferating naevus cells, we are using the proliferation marker Ki-67 in combination with the above selected markers. Preliminary results show high levels of Melan A and S100 expression in the epidermal and superficial dermal component of naevi, however, there is a loss of Melan A staining, with a persistence of S100 staining in the deeper dermis. In some cases, nests of naevus cells appear to express high levels of OCT 4, while only a few – yet some, express NANOG and NGFR P75. These preliminary results support the previous finding of a decrease in melanocyte specific markers in deeper dermal nests with a possible Schwann cell phenotype of these deeper naevus cells. The presence of stem cell markers in naevus tissue supports the hypothesis that at least some naevus cells may arise from stem cells, and not from differentiated melanocytes.

Advertisement from our sponsor: