This review provides a comprehensive overview of the anti-cancer potential of the most common single polyphenolic compounds, such as curcumin, resveratrol, epigallocatechin-3-gallate (EGCG), quercetin, and genistein (Figure 1), known to modulate the activity and expression of MMP-2 and MMP-9. The gene discussed is MMP9; the disease is cancer.