CD44 and breast cancer: In cloned spheres derived from breast cancer cells, the expression of Cav-1 is significantly downregulated, and inhibition of Cav-1 can upregulate indicators related to tumor stemness (CD44/CD24), promote the self-renewal ability of breast cancer stem cells, and thus promote the malignant tumor behavior of breast cancer, such as EMT, invasion and metastasis (Yoon et al., 2019).