Given that our model for conditional PAK4 gene depletion in the mouse mammary gland displays no apparent defect in organ development and function, this can serve as a useful model to study the in vivo role of PAK4 in breast cancer through crossing these mice with mammary tumor models such as MMTV-PyMT and MMTV-Her240–42. This evidence concerns the gene PAK4 and breast carcinoma.