ALDH1A1 and medical procedure: Taking into consideration; 1) the strong elevation of the expression of CD44v6 isoform in FR cells compared to sensitive cells (Figures 2B, C); and 2) that sphere/CICs located in tumor spheres are more resistant compared to Sphere/ALDH1(+)/CD133(+)/EpCAM(+) cells and primary parental tumor cells (Figure 2F), we concluded that CD44v6 splicing likely defines a colorectal CIC population with increased drug resistance properties.