Figure 2

Thiostrepton reduces SC subpopulations in HCT-15 and HT-29 human colon cancer lines. (a) HCT-15 and HT-29 cells were treated with dimethyl sulfoxide (DMSO as a vehicle control, Veh) or the indicated concentrations of thiostrepton for 48 h before flow cytometry was used to measure the percentage of the CD44⁺ subpopulation, which is indicated by the number shown in the upper-right of each quadrant. Data in the right bar graph are mean±S.D. from three independent determinations. *P<0.05 when compared with vehicle control by Student’s t-test. (b) Vector control (pBABE ctrl) and Snail-overexpressing (Snail OE) clones established from HCT-15 cells were treated with DMSO (veh), oxaliplatin (Oxa, 25 μM), and thiostrepton (Thio, 5 μM) for 48 h before their CD44⁺ subpopulations were measured. (c) Wild-type (WT) and oxaliplatin-resistant (r29) HT-29 cells were treated with DMSO and the latter were incubated with 5 and 10 μM thiostrepton for 48 h before their CD44⁺ subpopulations were analyzed. (d) Wild-type HT-29 cells were treated with DMSO, oxaliplatin, and thiostrepton as above described except their CD133⁺CD44⁺ (double positive) subpopulations were measured. (e) The remaining portions of the double-positive subpopulations in the freshly isolated CD133⁺CD44⁺ HT-29 cells were examined after they were incubated with DMSO, 5 and 10 μM thiostrepton for 48 h