During
melanoma progression, migrating cells must cross human dermis, a
type I collagen-rich tissue. We have show that MMP-1 and MMP-2 act in a cumulative manner in the in vitro invasion of a three-dimensional
type I collagen matrix by
melanoma cells. Two
melanoma cell lines (M1Dor and M3Da) previously reported to secrete
proMMP-2 in a direct relationship with their tumorigenic potential into nude mice were used (F. Capon et al., 1999, Clin. Exp.
Metastasis 17, 463-469). The highly tumorigenic cell line (M3Da) displayed a five-fold faster migration rate in
type I collagen matrix, compared to its lower tumorigenic counterpart (M1Dor). In parallel, activation of
proMMP-2 was evidenced in M3Da- but not M1Dor-populated
collagen lattices. Such enzyme activation was associated with a significant decrease in
TIMP-2 and
TIMP-1 production. Agents known to interfere with
proMMP-2 activation, i.e., excess
TIMP-2,
furin convertase inhibitor, and alphavbeta3 blocking antibody, reduced by 30-40% the
type I collagen invasive capacity of M3Da cells. By comparison,
batimastat, a wide-spectrum
MMP inhibitor, exhibited a more pronounced inhibitory effect (>70%). It suggested that other
collagenases than MMP-2 could participate in
type I collagen invasion.
Collagenase-3 (MMP-13) was produced at low levels by
melanoma cells whatever the cell culture conditions. In contrast, M3Da and M1Dor cells secreted
collagenase-1 (MMP-1) following 48 h of culture on
plastic dishes. Growing
melanoma cells in
type I collagen gel did not modify
enzyme production, but induced
proMMP-1 activation in M3Da but not M1Dor cell-populated lattices. Blocking the
plasmin-mediated
proMMP-1 activation by
aprotinin inhibited
type I collagen gel invasion by 30%. Since the combination of
aprotinin and
furin convertase inhibitor reduced
collagen invasiveness by
melanoma cells to a level comparable to that attained with
batimastat, we conclude that both MMP-2 and MMP-1 are involved in such tissue invasion.