APC and breast cancer: Both adenomatous polyposis coli (APC) and APC2 can regulate β-catenin/Wnt signaling12, 13, 14 and both are expressed in human mammary epithelium.15, 16, 17 Reduction of APC through loss of heterozygosity,15, 18 promoter hypermethylation16, 19, 20, 21, 22 and somatic mutation23 has been reported in breast cancers.