PAK1 and neoplasm: This conclusion is strongly supported by the observation that the numbers of tumours in the small intestine of PAK1 heterozygous (het) APC∆14/+ and PAK1 knockout (KO) APC∆14/+ mice were reduced by over 50% compared to PAK1 wild type (WT) APC∆14/+ mice (Fig. 2a).