Differentiation, proliferation and adhesion of human neuroblastoma cells after treatment with retinoic acid

Because of the known property of spontaneous regression in stage IVS of neu roblastoma all attempts are made to elucidate whether differentiation induc ers possibly could be applied for neuroblastoma therapy. Here we examined t he influence of retinoic acid (RA) in vitro on differentiation, proliferati on and adhesion of 10 permanent and 4 primary cell lines as well as of seve ral SCID-mouse tumour transplants. In general, after RA treatment morpholog ically different cell types which are characteristic for neuroblastoma cell s have changed. N (neuronal)-type cells prolonged their neuronal processes, whereas S (epithelial. substrate-adherent. Schwann cell-like)-type cells l ost their adherence to substratum and became apoptotic. Additionally. the r eactions of all neuroblastoma cell lines with monoclonal antibodies against beta-tubulin (for neuronal cells) and glial fibrillary acidic protein (for epithelial cells) were determined. The anti-proliferative effect of all-tr ans-RA as well as 13-cis-RA was more profound in S-type cells (up to 40% in primary cell lines). To elucidate the role of adhesion molecules during ne uronal cell differentiation. we have analysed the adhesion of neuroblastoma cells on poly-D-lysin precoated plates under RA. influence. While N-type c ells displayed an increased adhesion, all S-type cell lines as well as all primary cell lines exhibited a reduced adhesion(IMR 5 and IMR-32: p < 0.001 ; JW, SR and PM: p < 0.05). RA treatment increased predominantly the tested antigens (HCAM, ICAM-1, NCAM, PECAM-1, VCAM-1, cadherin, FGF-RI IGF-R, NGF -R, TGF-beta/1, NF200, NF160, NF68, NSE, HLA-ABC) in all cell lines indepen dently of their phenotypes (TGF-beta 1: p < 0.001; NF68: p < 0.01; PECAM-1 and NGF-R: p < 0.05). In recultured SCID-mouse-passaged tumour cells antige ns were down-regulated (FGF-R: p < 0.01), but increased again after RA infl uence (TGF-beta/1: p < 0.05). In summary, the RA differentiation model demo nstrates the possibility to interfere in cell adhesion and to diminish grow th potential both in N-type as well as S-type neuroblastoma cells.