miR-34a together with miR-520c-3p, miR-520b-5p, and miR-587-5p inhibit metastasis and cancer stemness in BC by targeting CD44. Upregulation of these miRNAs increases the efficiency of HER2-targeting strategies and would be foreseeable that their use may conquer TRA resistance more effectively [231]. This evidence concerns the gene CD44 and breast cancer.