A number of studies report that the activation of various group I PAKs (PAK1 and PAK3) results in the interaction/activating of the α isoforms of paxillin in different cell lines (including the fibroblast cell line, 3Y1, and NRB and CHO.K1 cells) [155,156,157]; the activated PAK1 down-regulated p130CAS in airway smooth muscle cells [158], and PAK4 activation is needed for stimulation for the activation of paxillin in lung cancer cells [159], as well as studies reporting that PAK4 mediates the activation of paxillin in PAK4-transfected MDCK cells [144] and in DU145 prostate cancer cells [160]. Here, PAK4 is linked to prostate cancer.