MMP9 and neoplasm: According to our results, over-expressing PDGF-D in ECC-1 cells significantly accelerated tumor growth and promoted cellular invasion via increasing the level of MMP2 and MMP9 (which could impair the basilar membrane); while silencing PDGF-D in Ishikawa cells impaired cell proliferation and inhibited the invasion, through suppressing the expression of MMP2 and MMP9.