MCs tryptase may contribute to cancer pathways triggered by the constitutive activation of NF-κB. In particular, tryptase may upregulate the levels of several target genes overexpressed owing to the pathological NF-κB activation, such as VEGF, IL-8, MMP-9, and uPA, thereby contributing to promote angiogenesis, invasion, and metastasis in a variety of tumors. This evidence concerns the gene MMP9 and cancer.