The phenomenon above could be explained as following: High cell density in tumor induces integrin αvβ6 and Ets-1 expression, which promote MMP-9 secretion for colon cancer cells,increasing the degradation of extracellular matrix (ECM),which constitutes the molecular biological basis for a self-perpetuating system of tumor invasive growth in colon cancer progression. The gene discussed is MMP9; the disease is neoplasm.