Thus, ABCB1 is more like a downstream gene that is regulated by hyaluronan–CD44 interaction-activated signalling, rather than coregulated with CD44. Nevertheless, the role of the hyaluronan–CD44 interaction in cell invasion was contradicted in other studies; CD44 could bind to high molecular weight hyaluronan to repress the invasion of several breast cancer cell lines [126], and the loss of CD44 was significantly associated with papillary carcinoma compared with benign papilloma among 160 specimens [127]. This evidence concerns the gene ABCB1 and breast cancer.