Although the exact molecular mechanisms by which hK1 promotes tumour growth and invasion have not been determined so far, two principal actions of hK1 may have a role: (1) promoting tumour cell invasion of extracellular matrix by its protease activity, directly or through the activation of metalloproteinases (MMPs) (Tschesche et al, 1989; Desrivieres et al, 1993; Menashi et al, 1994; Leeb-Lundberg et al, 2005; Stone et al, 2009) and (2) activating kinin receptors, either directly (Biyashev et al, 2006) or through the generation of kinins (Madeddu et al, 2007). This evidence concerns the gene HK1 and neoplasm.