In addition, RHAMM interacts with CD44 to activate ERK1/2 in breast cancer cell lines [26], and CD44 is reported to upregulate MDR1 microRNA-21 (miR-21), resulting in MDR1 (multi drug resistance protein 1) or anti-apoptotic protein Bcl2 in breast cancer cells [38,39]. Here, HMMR is linked to breast cancer.