We compared ABCB1 gene expression levels in the parental human colon carcinoma cell line HCT116, that is heterozygous for an in-frame Δ45 deletion in exon 3 of the β-catenin gene, in the HAB-18mut and HAB-68mut as well as in the HAB-85wt and HAB-92wt knockout strains of HCT116 cells, in which either the wt or the mut β-catenin allele was ablated by homologous recombination (Kim et al, 2002). This evidence concerns the gene ABCB1 and colon carcinoma.