Mesothelioma-initiating cells were selected from human primary samples by culturing the cells in HAM F12/DMEM medium supplemented with 1% PS, 20 ng/mL of EGF, 20 ng/mL of β-FGF, 4 μg/mL of IGF, 0.2% v/v B27, followed by selection by flow cytometry based on Oct4, Nanog, SOX2 and ABCG2 expression. In this subpopulation, ABCB5 expression (mRNA and protein using antibody SAB1300315 from Sigma) was increased. The gene discussed is SOX2; the disease is mesothelioma.