MMP9 and cancer: ECM degradation is crucial to cellular invasion, suggesting that matrix-degrading proteinases determine whether MMP-2 and MMP-9 are involved in the inhibition of invasion, motility, and adhesion of cancer cells by galangin; therefore, we investigated the inhibitory effect of galangin on TPA-induced MMP-2/-9 enzyme activity by using gelatin zymography under a condition of serum starvation.