RAC1 and breast cancer: Moreover, although the cytoplasmic and nuclear distribution patterns of both β-catenin and RAC1 were dysregulated upon KRT19 suppression in breast cancer cells, and KRT19 knockdown led to a dramatic decrease in nuclear β-catenin and RAC1 levels, in colon cancer cells, KRT19 knockdown resulted in dysregulation of β-catenin localization but had no effect on RAC1 localization (Figure 5a).