PAK1 and neoplasm: Except for the direct effect of PAK1 on cancer growth/metastasis, as identified to other molecules down the Kras pathway, we have discovered a role of PAK1 in the tumour immune response and the TME of PDA by showing that the inhibition of PAK1 decreased pancreatic tumour growth and stimulated anti-tumour immunity by down-regulation of PD-L1 (programmed death-ligand 1) expression by PC cells [8,9], that PAK1 is expressed in the PSCs of human PC samples, and that inhibition of PAK1 decreased the proliferation and increased the apoptosis of the PSCs by inhibiting the activation of PSCs [9].