NEUROTROPHIN STIMULATION OF HUMAN-MELANOMA CELL INVASION - SELECTED ENHANCEMENT OF HEPARANASE ACTIVITY AND HEPARANASE DEGRADATION OF SPECIFIC HEPARAN-SULFATE SUBPOPULATIONS

Heparanase is an endo-beta-D-glucuronidase, the enzymatic targets of w hich are the glycosaminoglycan chains of heparan sulfate proteoglycans . Elevated levels of heparanase are associated with the metastatic pot ential of melanoma cells. Treatment of murine and human melanoma cells with the prototypic neurotrophin nerve growth factor (NGF) increases the production of heparanase by melanoma cells. We reported previously that physiological concentrations of NGF increased in vitro Matrigel invasion of early-passage human brain-metastic 70W melanoma cells but not melanoma cells metastatic to other sites or nonmetastic melanoma c ells. Here we found that treatment of 70W melanoma cells with neurotro phins other than NGF or NT-3 did not influence invasion. Mutants of NG F that do not bind to the neurotrophin receptor p75(NTR) mRNA, there w as a reduction in NGF and NT-3 binding, and the neurotrophins failed t o enhance Matrigel invasion. To study the properties of heparanase in NT-regulated malignant melanoma invasive processes, we developed a sen sitive heparanase assay consisting of purified [S-35]heparin sulfate s ubpopulations separated by agarose gel electrophoresis. Incubation of 70W cells with NGF or NT-3, but not brain-derived NT factor, NT-4/5, o r mutant NGF, resulted in increased release of heparanase activity tha t was capable of degrading a subpopulation of heparan sulfate molecule s.