270 Phenotypic plasticity of melanocytes derived from human adult skin

Abstract

In previous work we have shown that adult human melanocytes cultured in a defined, specific mitogen-free medium, Mel-mix became bipolar, unpigmented and highly proliferative. Furthemore, in these cells the expression of TRP-1 and c-kit disappeared and EGFR receptor and nestin expression was detected, indicating a phenotypic switch toward dedifferentiation. In the present work we used high throughput mRNA sequencing analysis to compare the dedifferentiated melanocytes to mature cells. Immunohistochemistry showed the loss of MITF and Sox-10 expression in the dedifferentiated cells and flow cytrometry detected the expression of characteristic markers of mesenchymal stem cells. During dedifferentiation the expression of E-cadherin was reduced and the expression of fibronectin and oncofoetal fibronectin was elevated, confirmed by western blot. The dedifferentiated melanocytes were able to differentiate into adipogenic, osteogenic and chondrogenic phenotype given the appropriate in vitro environment. The extensive characterization of these cells revealed relevant similarities with undifferentiated melanoma cells, indicating that phenotype switching driven by environmental factors is a general characteristic of melanocytes that can occur independent of malignant transformation. These in vitro dedifferentiated melanocytes can be used to investigate the non-genetic plasticity of melanoma cells, a process that play a crucial role in metastasis, dormant cancer cell development and in therapy resistance.