Studies have reported that miRNAs, such as miRNA-150 [32], miRNA-34a [33], miRNA-200c [34], miRNA-330-5p [35], and miRNA-143 [36], negatively regulated CD44 expression in nasopharyngeal, esophageal, ovarian, non-small cell lung, and breast cancers, inhibiting the invasive and metastatic ability of tumor cells and tumor stemness. This evidence concerns the gene CD44 and breast cancer.