Transformation of stem cells into cancer stem cells due to activation of OCT4, RNF51, CD44, and CD133 gene expression; increased activity of Wnt/β-catenin pathway; modulation of chromatin organization leads to reduced efficiency of the mismatch repair system; increased MSI; reduced apoptosis rate; inhibition of the expression of miR-126 and activating the PI3K-AKT-mTOR pathway (in gastric cancer). This evidence concerns the gene CD44 and cancer.