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 neuroblastoma all attempts are made to elucidate whether differentiation inducers possibly could be applied for neuroblastoma therapy. Here we examined the influence of retinoic acid (RA) in vitro on differentiation, proliferation and adhesion of 10 permanent and 4 primary cell lines as well as of several SCID-mouse tumour transplants. In general, after RA treatment morphologically different cell types which are characteristic for neuroblastoma cells have changed. N (neuronal)-type cells prolonged their neuronal processes, whereas S (epithelial, substrate-adherent, Schwann cell-like)-type cells lost their adherence to substratum and became apoptotic. Additionally, the reactions 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-trans-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 neuronal cell differentiation, we have analysed the adhesion of neuroblastoma cells on poly-D-lysin-precoated plates under RA influence. While N-type cells 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-R, IGF-R, NGF-R, TGF-beta/1, NF200, NF160, NF68, NSE, HLA-ABC) in all cell lines independently 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 antigens were down-regulated (FGF-R: p < 0.01), but increased again after RA influence (TGF-beta/1: p < 0.05). In summary, the RA differentiation model demonstrates the possibility to interfere in cell adhesion and to diminish growth potential both in N-type as well as S-type neuroblastoma cells.