39 DEVELOPMENTAL/NEUROLOGY/FOLLOW-UP

Abstract

In the last few years we have been able to produce a large body of evidences that ARA-C is capable of inducing neuronal differentiation of human neuroblasts in vitro. Three different human neuroblastoma (NB) cell lines have been tested with ARA-C, LAN-1, LAN-5 and Gl-ME-N. ARA-C actually modifies both surface and cytoskelcton markers' expression while inducing substained morphologic differentiation of all three NB cell lines. Specifically, ARA-C induces concentration, dependent growth inhibition, neurite sprouting, and neurofilaments expression in Gl-ME-N cells, while decreasing the level of membrane antigens specific for neuroblast cells. The maximum effect was obtained using a dose as low as 0.1 mgml. Similar modifications were recorded inducing bolh LAN-1 and LAN-5 human NB cells with ARA-C. The fact that ARA-C treatment of human NB cells started one day after plating with no subsequent decrease in cell viability in the cultures, strongly suggests that its effects were not the result of selection of more differentiated cells by differences in plating efficiency or ARA-C cytotoxicity. This conclusion was supported by time-lapse pholomycroscopic observations, which clearly showed individual ARA-C treated NB cells undergoing morphologic differentiation. The results rise the suspicious that the interpretation of ARA-C mechanisms of action on P19 carcinoembrional cells is overscmplicistic. We actually do not thing thai “…one can sclectively enrich for neurons by treating the induced culture with the antimetabolyte ARA-C” as suggested by Chung JJM et al. (Cell 64, 189-200, 1991). In fact, as previously demonstrated by our group, ARA-C is not onlv capable of arrest the overgrowing of non-neuronal cells, but is actively capable of pushing neuroblast cells along the neuronal differentiation pathway.