Several studies on the prognostic significance of ABCG2 expression in colorectal cancer have been conducted; however, they have yielded inconsistent results [26,30,44,45,46] due to heterogeneity in the numbers of analysed samples and patient enrolment, stratification schemes, applied treatments and measurement of ABCG2 gene and ABCG2 protein expression. Here, ABCG2 is linked to colorectal cancer.