SUPPRESSION OF BASEMENT-MEMBRANE TYPE-IV COLLAGEN DEGRADATION AND CELL INVASION IN HUMAN-MELANOMA CELLS EXPRESSING AN ANTISENSE RNA FOR MMP-1

During progression from benign nevus to vertical growth phase melanoma , melanocytes acquire the ability to invade into the dermis. This proc ess requires rupture of the basal lamina and dissolution of dermal typ e I collagen. Metastases-derived human melanoma MIM cells have an inva sive ability in vitro which is dependent on metalloproteinases. In the present study we analysed the role of type I collagenase (MMP-1) in m elanoma invasion using MIM cells in which the constitutive expression of MMP-1 was suppressed by stable transfection with a plasmid vector e xpressing a 777 bp antisense fragment of MMP-1 genomic DNA. Two clones were isolated in which MMP-1 mRNA expression was blocked by 90-96% wi th a corresponding loss in protein synthesis. In their morphological a ppearance and growth rate in vitro these cells were indistinguishable from wild type cells or control cells transfected with the same vector expressing the MMP-1 fragment in the sense orientation. Their mRNA an d protein levels for type IV collagenase (MMP-2) were unchanged as ass essed by Northern and Western blot analyses and by gelatin zymography. However, when the invasive ability of the cells was measured, we foun d that in addition to type I collagen, invasion through type IV collag en and a reconstituted, type IV collagen-containing basement membrane (Matrigel) were also significantly inhibited as compared to normal or sense-transfected cells. The results indicate that despite the presenc e of functional MMP-2, degradation of type IV collagen matrices by the melanoma cells was dependent on expression of MMP-1. (C) 1997 Elsevie r Science B.V.