We found an overall lower PAK4 expression in early lesions compared with late-stage PyMT-driven tumors; that PAK4 expression is consistently less in the tissues harvested from PyMT;PAK4MEp−/− mice as compared with control; that residual PAK4 expression occurred specifically in tumor areas of PyMT;PAK4MEp−/− tissues (Supplementary Fig. 2j, k). Here, PAK4 is linked to neoplasm.