Statistical analyses revealed that in tumor tissues the average promoter methylation status of ABCB1 significantly correlated with that of ABCG2. However, we did not find a correlation between the methylation status of ABCB1 or ABCG2 and that of CCND2, DAPK1, GSTP1, HIN-1, MGMT or RASSF1A determined previously [45]. Here, MGMT is linked to neoplasm.