Hepatocyte growth factor/scatter factor (HGF/SF) plays a crucial role in cancer cell migration, matrix adhesion, invasion, and angiogenesis, via the phosphorylation of the c-met tyrosine kinase. This study examined the ability of NK4, a recently discovered HGF/SF variant, to inhibit the influence of HGF/SF on cell-matrix interaction, paxillin phosphorylation, and invasion of prostate cancer cells. HGF/SF was shown to dramatically enhance tumour cell motility, invasion, cell-matrix adhesion, together with an increase in the degree of paxillin phosphorylation and formation of focal adhesion complexes. However, these HGF/SF-induced effects were suppressed by the presence of NK4. NK4 effectively inhibited the degree of HGF/SF-induced paxillin phosphorylation and matrix adhesion. As a consequence, the matrix invasion of these prostate cancer cells was also suppressed by NK4. In conclusion, this study shows that these HGF/SF-enhanced events, which are critical steps in metastasis, can be inhibited through the addition of NK4, thus warranting further in vivo studies on the implication of NK4 as a potential antimetastasis agent in prostate cancer.