ABCG5 and breast cancer: For example, ABCC3 increases in expression when ABCC2 is disrupted in Dubin-Johnson Syndrome (Donner and Keppler, 2001; König et al., 1999), and ABCG5 and ABCG8 both increase in expression when ABCG2 (a gene that confers breast cancer xenobiotic resistance in humans) is knocked out in mice (Huls et al., 2008).