To evaluate the role of CD109/EGFR in the maintenance of the cancer stem cell population, we examined the self-renewal property of control A431, CD109-KO, CD109KOEGFR, CD109-KOCD109G, CD109-KOCD109S, or CD109KOEGFR+CD109G cells using an in vitro spheroid formation assay. This evidence concerns the gene EGFR and cancer.