Colon cancer stem cells (colon CSCs), positive for cancer stem cell markers CD 133, CD 44, and ALDH1b1, were obtained from Celprogen (San Pedro, CA, USA). To maintain the cells in their undifferentiated state, colon CSCs maintenance media and specially coated cell culture flasks obtained from Celprogen were used. Cells were maintained in incubation at 37 ˝C and 5% CO2 as described earlier [37]. Cell cultures at approximately 80% confluence were used for all in vitro experimental procedures.