Figure 2

The CD133^high/CD44^high phenotypic cell population has high sphere-forming capacity in the three independent colon cancer cell lines HCT116, HT29 and DLD-1. Cells grown at standard culture conditions possessed the minority phenotypic subpopulations with high combined levels of expression of CD133 and CD44 (left panel; outlined by dashed squares). The sphere-forming efficiency of these cells was 1 of 66 for HCT116 cell line, 1 of 175 for HT29, and 1 of 118 for DLD-1 cell line. In contrast, bulk cancer cells could induce only a few loose flat colonies under non-adherent culture conditions. Induced spheroids retained original cell phenotypes (right panel).