SOX2 and cancer: Notably, loss of CD09 diminishes the expression of markers of pluripotency/cancer cell stemness (SOX2, OCT4 and NANOG, and CD44) (Figure 3) and self-renewal/tumorigenic potential (spheroid formation) in vitro in SCC cells (A431, FaDu), demonstrating that CD109 is required for the maintenance of the cancer stem cell population in SCC.