ALDH1A1 and cancer: Using the ALDEFLUOR (measuring ALDH1 activity) assay which reflects the activity of ALDH1 (Aldehyde dehydrogenase 1), one of the stem cell and cancer stem cell markers, it was demonstrated that DLD1-ARTN cells exhibited markedly increased percentages of ALDH1bright cells (17.7%) compared to DLD1-vec cells (2.9%, Figure 6C left panel).