In the present study, we evaluated CD133 expression in 21 tumor cell lines (Table 1) and found major populations of CD133-positive cells in Caco2 and HT-29 (both colorectal cancer cell lines), HUH7 (hepatocellular carcinoma cell line), and a minor population in FTC-133 (thyroid cancer cell line). This evidence concerns the gene PROM1 and neoplasm.