Effect of CDDO, CDDO-Im and CDDO-Me on the viability of colorectal cancer cells. A: 1×104 colon cancer cells (HT-29, HCT-15, HCT 8, HCT 116, Colo 201 or Colo 205) were seeded in each well of a microtiter plate in 0.1 ml of culture medium. Cells were allowed to adhere for 24 h before treating with CDDO or CDDO-Im or CDDO-Me at concentrations of 0 to 10 μM in triplicates for 72 h. Cell viability was measured by MTS assay using CellTiter AQueous assay system from Promega. Similar results were obtained in 4 independent experiments. B: Morphological changes in cell cultures (HT-29 and HCT-15 cells) treated or not with CDDO-Me for 72 h as visualized by light microscopy. Similar results were obtained in two independent experiments.