SPP1 and melanoma: For further analysis, we focused on six significantly regulated genes from four different functional groups: the transcription factors FOSL1 and EGR1, the secreted proteins OPN and IGFBP3, the phosphatase DUSP4, and the membrane protein TAAL6. We monitored their expression levels in human melanoma cell lines compared to normal human epidermal melanocytes (NHEM).