EGFR and neoplasm: In contrast, forced simultaneous expression of both EGFR and GPI-anchored CD109 in CD109-KO cells restored their self-renewal ability, as evidenced by the capacity of CD109-KOEGFR+CD109G cells to form tumor spheroids reaching comparable levels to that of control A431 cells (Figure 7B), suggesting that GPI-anchored CD109 is important for the maintenance of the stemness of SCC cells.