These observations might be linked to different tumor subtypes and stages, since in an in vivo study, initial progression of WD PCa tumors was dependent on matrix metalloprotease 9 (MMP-9) production by mast cells, which was no longer essential for post epithelial-to-mesenchymal transition (EMT) stages, where PD tumors were MMP-9 self-competent (16). The gene discussed is MMP9; the disease is Wilson disease.