PLAU and cancer: Pre-clinical studies show that HER2 accelerates cellular adhesion and migration and therefore plays a key role in tumour cell invasion.20–23 Certain clinical studies indicate that in some cancer types HER2 stimulates the invasion of tumour cells with the effect on the accelerated release of proteolytic enzyme uPA and its inhibitor (PAI-1)24–27, whereas other studies did not confirm this assumption.28,29 The international coordinated guidelines, adopted at the conference in St.