MMP2 and breast cancer: It has been observed that the Hv1 silencing by siRNA reduces the MMP-2 expression in MDA-MB-231 highly metastatic cells (Wang et al., 2012), which suggests that the activity of Hv1 is supporting invasion and metastasis in breast cancer cells, by maintaining the perfect levels of both intracellular and extracellular pH for secretion, activation and distribution of proteases involved in extracellular matrix digestion such as MMP-2.