Nerve growth factor effects on human and mouse melanoma cell invasion and heparanase production

The role of growth factor networks in regulating the progression of human melanocytes towards tumorigenicity and ultimately the malignant phenotype is poorly understood. In particular, the autocrine and paracrine influences that modulate cellular invasion and extracellular matrix degradative enzymes of melanoma cells remain undefined at the molecular level. We report here that nerve growth factor (NGF) can modify some metastasis‐associated cellular properties of human and mouse melanoma cells. Treatment of early‐passage human metastatic melanoma cells (MeWo) or their variants (3S5, 70W) with biologically active 2.5S NGF resulted in (a) delayed density‐dependent inhibition of melanoma cell growth; (b) increased in vitro invasion through a reconstituted basement membrane; and (c) time‐ and dose‐dependent induction of heparanase, a heparan‐sulfate‐specific endo‐β‐D‐glucuronidase associated with human melanoma metastasis. These effects of NGF were most marked in the 70W brain‐colonizing cells (70W > MeWo > 3S5). The NGF enhancement of heparanase secretion was not species‐specific, since it was also observed in murine B16 melanoma cells; the highest NGF stimulation of heparanase was found in brain‐colonizing murine B16‐B15b variant (B16‐B15b > B16‐BL6, B16‐F10, B16‐F1). NGF also increased the invasive capacity of the human 70W and murine B16‐B15b sublines in a chemoinvasion assay performed with filters coated with purified heparan sulfate proteoglycan (HSPG). The enhancement of chemotactic response and heparanase production was detected at NGF concentrations sufficient to fully saturate both low‐ and high‐affinity NGF receptors (NGFR), the neurotrophin receptor (p75) and the trkA gene product, respectively. The results suggest that, in addition to the effects of NGF on cellular development and differentiation within the peripheral and central nervous systems, NGF can exert changes in the invasive properties of neuroectoderm‐derived melanoma cells.