A variety of stimuli, such as cytokines and treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), are able to activate transcription factors like nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1) leading to MMP-9 expression [88]. This evidence concerns the gene NFKB1 and neoplasm.