MMP1 and neoplasm: Two biochemical markers associated with aggressive human cancers have also been observed in lgl tumours: secretion of Collagenase IV [11] and Matrix Metallo-Proteinase 1 (MMP1) [12] both involved in basement membrane degradation; the latter has further been shown to be essential for lgl cells spreading because lgl-MMP1 double mutant cells show a strong reduction in the ability to leave primary lesions [12].