ABCG2 and carcinoma: Comparing tumor and normal tissues, three of the five analyzed genes showed a significant lower expression in tumors than in healthy control tissues (ABCB1, p<0.0001; ABCC2, p<0.005; ABCG2, p<0.0001), whereas ABCC1 expression was significantly up-regulated in the carcinomas (p<0.0001).