We conclude that the strong antitumor activity of arazyme against murine B16F10-Nex2 metastatic melanoma could be due to the direct activity of the active protease on tumor cells in combination with the cytotoxic arazyme-specific immunoglobulins cross-reactive with MMP-8 expressed by tumor cells, making this bacterial metalloprotease a promising candidate for metastatic disease control. The gene discussed is MMP8; the disease is metastatic melanoma.