Identification of secreted phosphoprotein 1 (SPP1) as a potential melanoma driver. (A) Schematic flowchart of gene selection in GSE15605 and GSE46517 from GEO database. (B) Heatmap of 70 genes that differentially expressed among normal skin (NS), primary (PM), and metastatic (MM) melanoma in both GSE15605 and GSE46517. (C) SPP1 expression in NS, PM, and MM from GSE15605 and GSE46517. The number of sorts: N (NS) = 16, N (PM) = 46, and N (MM) = 12 in GSE15605; N (NS) = 7, N (PM) = 31, and N (MM) = 73 in GSE46517. (D) SPP1 expression in NS and melanoma tissue from Oncomine database. (E) SPP1 expression in PM and MM from Xu et al., 2018(GSE8401) and TCGA. The number of sorts: N (PM) = 31 and N (MM) = 52 from Xu et al., 2018(GSE8401); N (PM) = 103 and N (MM) = 369 from TCGA. (F) SPP1 expression in three mutational signatures (BRAF, NF1, and RAS) and wild types (WT) of melanoma based on GEPIA (Gene Expression Profiling Interactive Analysis). The number of sorts: N (NS) = 558, N (BRAF) = 147, N (NF1) = 27, N (RAS) = 91 and N (WT) = 47. Error bars represent standard deviation (SD). P-values were calculated using unpaired two-tailed Student's t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.