Some studies have confirmed that MRP4 participated in cellular excretion of resveratrol 3-O-glucuronide and resveratrol 4′-O-glucuronide [18], the inhibition of urinary excretion of methotrexate [19], cellular excretion of the raloxifene sulfates in breast cancer patients [20], the process of human obstructive cholestasis [21], and so on. Here, ABCC4 is linked to breast cancer.