Role of glucocorticoid hormones in the differentiation of the human neuroblastoma cell line SK-N-SH

It is known that glucocorticoids (Gc) are involved in the differentiation of primordial cells derived from the neural crest. Neuroblastoma, the most common extracranial solid tumor of childhood, is a tumor derived from the neural crest sympathoadrenal lineage. Previous data performed in our laboratory have demonstrated that glucocorticoid receptors (GRs) are expressed in the SK-N-SH cells, a human neuroblastoma cell line. It is known that the human GR gene generates different transcripts differing in the 5’ non-translated forms of exon 1. In order to get further information on the GR gene expression and on the mechanism of action of Gc on neuroblastoma cells, experiments have been performed to study the presence of different transcripts of GR in SK-N-SH cells. The RT-PCR analysis performed in our laboratory revealed that three GR-gene derived transcripts (1A1, 1A3 and C) are present in SK-N-SH cells. In a second series of experiments, the effect(s) of the exposure to Dex for 6 days on the number and/or differentiation of SK-N-SH cells has been investigated. It has been found that Dex addition produces a dose-dependent (from 10-8 to 10-6 M) increase of the number of SK-N-SH viable cells, as evaluated by the MTT method. In addition, Dex treatment induces a trans-differentiation of the neuroblast-like component of SK-N-SH cells toward an epithelial-like phenotype. This phenotypic modification is apparently accompanied by a remodeling of cell cytoskeleton and redistribution of F-actin, formation of stress fibers and loss of ruffles and lamellipodia present in untreated cells, as indicated by a staining with fluorescent phalloidine. It has further been analyzed whether Dex could modify the chemomigratory response of SK-N-SH cells in the presence of a chemoattractant by a microchemotaxis assay. A 6-day treatment of SK-N-SH cells with different doses of Dex (10-10 M - 10-6M), significantly decreases their chemomigratory response to fetal bovine serum. In summary, the data here reported suggest that: a) three different exon1-derived transcripts (1A1, 1A3 and C) of the GR gene are present in SK-N-SH cells; b) the chronic treatment with Dex induces an increase of cell proliferation and/or survival; c) under these cirmcumstances, Dex stimulates a differentation of SK-N-SH neuroblastoma cells to a quite homogeneous epithelial-like phenotype; d) Gc may affect the organization of the actin cytoscheleton of SK-N-SH neuroblastoma cells; e) Gc may also affect in an inhibitory way the migratory activity of these cells. These results suggest that SK-N-SH cells may represent a useful tool to study the molecular mechanisms through which Gc act on the differentiation of neural crest-derived cells.