Guided by the selectivity against Cre-positive cells observed in the tumors that arose in PyMT;PAK4MEp−/− mice; the Ingenuity Pathway Analyses upon PAK4 knockdown described above and an observation in glioblastoma28, we analyzed potential senescence-like features in breast cancer cells upon PAK4 depletion. The gene discussed is PAK4; the disease is breast cancer.