MMP9 and cancer: In numerous types of cancer, elevated plasma levels of soluble gelatinases, such as MMP-2 and -9, have been positively correlated with a higher incidence of MMP-9 expression, and appear to be regulated by the binding of multiple factors, including nuclear factor κ-light-chain-enhancer of activated B cells and the activator protein 1, to their response elements (13,25).