Mitogenic effect of neurotrophic factors on human IMR 32 neuroblastoma cells

The effect of growth factors with neurotrophic properties on proliferation of the human IMR 32 neuroblastoma (NB) cell line was studied. A colorimetric proliferation assay and an anchorage-dependent cell culture system were used. Basic fibroblast growth factor (bFGF), nerve growth factor (NGF), neurite-inducing factor (NIF), ciliary neurotrophic factor (CNTF), and a cell-free extract from selected embryonic chick eye tissues (CIPE) were assayed for their capacity to control proliferation. Basic FGF, NGF, and CIPE stimulated proliferation of IMR 32 NB cells in serum-containing culture conditions. The NIF and CNTF had no effect. The concentration of bFGF required to induce half-maximal cell growth was 4.6 +/- 1.8 ng/ml, but the half-maximally effective dose of NGF was 7.5 +/- 2.7 ng/ml. In combination these two growth factors were additive within a small concentration range. In serum-free culture conditions bFGF affected both proliferation and cell differentiation by promoting neurite growth and cell aggregate formation. In contrast, NGF induced cell neurite outgrowth only. These results, in conjunction with the evidence that bFGF-like molecules are present, in IMR 32 NB cells may support the notion that NB cells regulate their proliferation by an autocrine mechanism. Basic FGF and NGF, two distinct neurotrophic factors, appear to be involved in the regulation of NB cell proliferation.