PAK4 and Familial prostate cancer: While neuronal substrates specific to PAK6 have not been identified, PACSIN1 (Syndapin 1), an F-BAR protein involved in synaptic vesicle recycling, is phosphorylated redundantly by PAK4, PAK5 and PAK6 in vivo[14] PAK6 is overexpressed in prostate cancer [15], and its targeted inhibition could potentially decrease growth of prostate tumors [11] or sensitize prostate cancer cells to radiotherapy [16].