Nerve growth factor receptors on human melanoma cells in culture (membrane receptors/cell culture/neural crest/binding assay)

Purified mousenerve growth factor (NGF) ra- diolabeled with 125wastested for its ability tobind toavariety ofdifferent cultured cells. NGFbinds readily tohumanand hamster melanoma cells butdoes notbind tomanyother cell lines. Thethree cell lines withthehighest number ofNGFre- ceptors werederived frommetastatic melanomas. Oneofthese lines, A875, wasstudied indetail andwasshown tohaveap- proximately 7X10$NGFreceptors percell with anassociation constant of1.0x109liters/mole. Thie useofthese cells incom- petition binding assays permits thedetection of0.25 ngofNGF invarious biologic fluids. NGFcanbeshown toincrease the survival, butnotthedivision, ofmelanoma cells maintained in mediumdepleted ofserumgrowth factors. This effect ofNGF asaspecific "survival factor" appears analogous toits effect on cultured sympathetic ganglion cells andonother cells derived fromtheneural crest. Nerve growth factor (NGF) (1)binds tospecific membrane receptors onthesurface ofrelatively fewcell types inculture. Itwill stimulate theoutgrowth ofaxons fromsympathetic ganglia, providing thebasis for anassay ofits biologic activity (2). Mouseneuroblastoma cells inculture havealso beenre- ported tohave specific NGFbinding sites (3). Inthis study we showthat thegreat majority ofcultured cells (fibroblasts and epithelial cells from various species, andnormal aswell astumor cells) have nodetectable NGFreceptors. Instriking contrast, humanandhamster melanoma cells haveabundant NGFre- ceptors. Theavailability ofcontinuous cell lines withlarge numbers ofhigh affinity NGFreceptors hasmadeitpossible todevelop acompetition binding assay that readily detects 0.1 biologic unit (1ng)ofNGF.