MMP9 and neoplasm: As MMP-13 is capable of activating MMP-9 by cleavage of the inactive pro-MMP-9 form [115,126,127], its action on MMP-9 activation can therefore promote tumour cell infiltration into the blood/lymphatic vessels at primary tumour sites, as well as the extravasation of invaded tumour cells from blood/lymphatic vessels at remote organs.