New Perspectives on Melanoma_ The Role of PAX3

Mostinterestinglyaproportionofpax3positive epidermal

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Unformatted text preview: but this downstream target of PAX3 was not present in normal epidermal melanocytes, suggesting differential roles for PAX3 in normal epidermal melanocytes and melanoma cells. Most interestingly, a proportion of PAX3‐positive epidermal melanocytes in normal skin show HES1 and Ki67 co‐expression, indicating their less differentiated proliferative phenotype. To clarify PAX3 roles in normal melanocytes and melanoma cells, we thought to analyse its direct target genes in these cell types. An intensive literature research was employed to identify the potential and likely PAX3 targets in normal melanocytes and melanoma cells. This generated a list of 56 genes, from which we selected 14 genes for further investigation, based on their significance for melanoma development and progression. Direct PAX3 binding to the selected genes in melanocytes and melanoma cells was assessed by ChIP‐qPCR. Differential expression of identified direct targets was then analysed in melanoma cells compared to normal melanocytes, by RT‐qPCR. Results distinguish genes that are commonly regulated by PAX3 in melanocytes and melanoma cells, from those that are restricted to melanoma cells. Further, we show that similar to its role in development, PAX3 controlled complex differentiation networks (via NES and SOX9) in both melanoma cells and melanocytes, in order to maintain cells in a less differentiated, stem cell‐like state. We also show that mediators of migration (MCAM and CSPG4) are common to both cell types, but are more highly expressed in melanoma cells. By contrast, PAX3‐ mediated regulation of melanoma cell proliferation (through TPD52) and survival (through BCL2L1 and PTEN) differs from that of melanocytes. v Abstract Conclusions and Significance: Our results suggest that previously identified roles for PAX3, as a regulator of an undifferentiated plastic state, and of cell proliferation, migration and survival, may operate in melanoma cells as well as in melanocytes of normal skin. By controlling these crucial cellular proce...
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