Ms. Stack et al., MODULATION OF MURINE-B16F10 MELANOMA PLASMINOGEN-ACTIVATOR PRODUCTIONBY A SYNTHETIC PEPTIDE DERIVED FROM THE LAMININ-A CHAIN, Cancer research, 53(9), 1993, pp. 1998-2004
Laminin is a large multidomain protein with diverse biological activit
ies. We previously demonstrated that intact laminin as well as an A ch
ain synthetic peptide (LamA2091-2108) stimulate tissue plasminogen act
ivator (t-PA)-catalyzed plasminogen activation. Here we report that La
mA2091-2108 increases t-PA production by the highly metastatic murine
melanoma cell line B16F10, with no effect on the parental B16F1 line,
which has a low metastatic capacity. Incubation of plasminogen with B1
6F10-conditioned medium results in direct activation of the zymogen to
plasmin. Furthermore, following incubation of B16F10 cells with plasm
inogen, plasmin is eluted from the cell surface. suggesting that these
cells contain binding sites for plasminogen/plasmin in close proximit
y to t-PA binding sites. Quantitation of t-PA activity using the synth
etic substrate Val-Leu-Lys-p-nitroanilide indicates a minimal 10-fold
increase in t-PA in the conditioned medium of B16F10 cells grown in th
e presence of LamA2091-2108, with no increased t-PA activity observed
in B16F1-conditioned medium. Similar results were obtained in immunoca
pture experiments which are specific for t-PA antigen. In addition, B1
6F10 melanoma-associated t-PA catalyzes the plasminogen dependent hydr
olysis of laminin. Together these data suggest that degradation of bas
ement membrane proteins by metastatic melanoma cells may release fragm
ents (such as LamA2091-2108) which stimulate both the production and a
ctivity of metastasis-associated proteinases such as t-PA, providing a
mechanism for augmentation of the metastatic capacity of B16F10 melan
oma cells.