Neuroblastoma cells contain a trophic factor sharing biological and molecular properties with ciliary neurotrophic factor.

Abstract

Ciliary neurotrophic factor (CNTF) is a protein supporting the in vitro survival of a characteristic spectrum of embryonic chicken and rat peripheral neurons. High-speed supernatants of extracts from two neuroblastoma (NB) cell lines-the mouse C 1300 N2a and the human IMR 32-mimic the effects of CNTF on identical target neurons. Promotion of survival is dose-dependent with an ED50 of 80 ,ug (IMR 32) and 140 ,Ag (C 1300 N2a) of protein per ml and saturable at plateau values for surviving neurons identical to those achieved with purified CNTF. Small amounts of a CNTF-like material are also detectable in medium conditioned by NB cells. The activity is destroyed by heat and trypsin and not blocked by antibodies to (mouse) nerve growth factor. Unlike the neurite-promoting and neuronal-survival modulating agent laminin, it cannot be depleted on poly(L-a-ornithine)-coated plastic surfaces. NB IMR 32 cell extracts were electrophoresed using NaDodSO4/ PAGE and transferred to nitrocellulose. Ciliary ganglion neurons seeded on the blotting paper in culture medium lacking CNTF ("cell blot") exclusively survive on two distinct bands with apparent molecular masses of 24 and 48 kDa. Twenty-four kilodaltons is the molecular mass of a CNTF purified from rat sciatic nerve. These results suggest that NB cells may contain a CNTF-like protein and provide further evidence that neurons may store neurotrophic factors. Purified (chicken) CNTF failed to affect proliferation and neurite growth of NB cells. The biological relevance of CNTF for NB cells, therefore, remains to be elucidated.Naturally occurring cell death is a process during the development of the nervous system that is important for morphogenesis and the establishment of proper neuronal connections (1). In several neuronal systems investigated, neuronal cell death is determined to varying extents by neurotrophic factors (NTFs) that are made available to neurons by their respective target tissues. A well-documented example of a NTF is nerve growth factor (NGF) whose structure, synthesis, and functions have been most extensively studied (2). Extrapolating from NGF (and target organ)-regulated neuron death, it seems reasonable to suggest that neurons as target cells to other neurons may supply these with NTFs (1, 3). However, evidence for NTFs of neuronal origin is still scarce (3), a major reason possibly being that their demonstration requires purified, large and homogeneous populations of neurons.We have found that adrenal medullary chromaffin cellsi.e., modified sympathetic neurons-store and secrete trophic activities that support the in vitro survival of a large number of neurons dissociated from embryonic and neonatal peripheral and central nervous tissues (4-6). The molecular characteristics of these agents have only partially been revealed, but they do not seem to resemble NGF. Neuroblastoma (NB) cells are closely related to sympathetic neurons and chromaffin cells. We report here that two NB cell lines, the human IMR 32 and mouse C 1300 N2a, contain a NTF activ...

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