In addition, GLI binding sites in the promoter region of six ABC transporters, namely ABCA2, ABCB1, ABCB4, ABCB7, ABCC2 and ABCG1, were confirmed in a recent study, and the inhibition of GLI1 reduced the expression of these ABC transporters in colorectal cancer cells [100]. Here, ABCG2 is linked to colorectal cancer.