To investigate whether the observed CRB3 and β‐catenin expression patterns in tamoxifen‐resistant tissues could be also found in vitro, we examined mRNA and protein levels of CRB3 and β‐catenin genes in luminal A breast cancer cells, MCF7, T47D, and corresponding tamoxifen‐resistant cells (LCC2 and T47D TamR). This evidence concerns the gene CRB3 and breast carcinoma.