SOX2 and melanoma: Interestingly, four genes known to be related to cancer cell stemness in malignant melanoma (ALDH1A3, BSG, NGFR, SOX2) [35] were expressed at significantly high levels in CTCs with a high “platelet signature” (p = 0.0204, 0.0012, 0.0183, 0.0200, respectively).