RESUMO
We have recently demonstrated that fibroblast growth factor (FGF)-2 promotes neuroblastoma cell differentiation and overrides their mitogenic response to IGF-I. However, the mechanisms involved are unknown. SK-N-MC cells were cultured with FGF-2 (50 ng/ml) and/or IGF-I (100 ng/ml) up to 48 h. Fluorescence-activated cell sorting analysis indicated that FGF-2 promotes G1/G0 cell cycle phase arrest. Gene expression by RT2-PCR and cellular localization showed up-regulation of p21. We then investigated whether FGF-2-induced differentiation of SK-N-MC cells (by GAP43 and NeuroD-6 expression) involves epithelium-mesenchyme transition interconversion. Real-time PCR (RT2-PCR) showed modulation of genes involved in maintenance of the epithelial phenotype and cell-matrix interactions (E-cadherin, Snail-1, MMPs). Zymography confirmed FGF-2 up-regulated MMP2 and induced MMP9, known to contribute to neuronal differentiation and neurite extension. Id1-3 expression was determined by RT2-PCR. FGF-2 induced Id2, while down-regulating Id1 and Id3. FGF-2 induced nuclear accumulation of ID2 protein, while ID1 and ID3 remained cytoplasmic. RNA interference demonstrated that Id3 regulates differentiation and cell cycle (increased Neuro-D6 and p21 mRNA), while d Id2 modulates epithelium-mesenchyme transition-like events (increased E-cadherin mRNA). In conclusion, we have shown for the first time that FGF-2 induces differentiation of neuroblastoma cells via activation of a complex gene expression program enabling modulation of cell cycle, transcription factors, and suppression of the cancer phenotype. The use of RNA interference indicated that Id-3 is a key regulator of these events, thus pointing to a novel therapeutic target for this devastating childhood cancer.
Assuntos
Diferenciação Celular/genética , Inibidor de Quinase Dependente de Ciclina p21/fisiologia , Fator 2 de Crescimento de Fibroblastos/fisiologia , Fase G1/efeitos dos fármacos , Proteína 1 Inibidora de Diferenciação/fisiologia , Proteína 2 Inibidora de Diferenciação/fisiologia , Proteínas Inibidoras de Diferenciação/fisiologia , Proteínas de Neoplasias/fisiologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Linhagem Celular Tumoral , Matriz Extracelular/fisiologia , Regulação Neoplásica da Expressão Gênica , Humanos , Neuroblastoma/genética , Interferência de RNA , RNA Mensageiro/metabolismo , Transdução de SinaisRESUMO
This case report presents a thirteen year-old boy who was diagnosed as having Hypomelanosis of Ito. The developmental history includes severe failure to thrive, and moderate atypical autism as well as diverse clinical and neuropsychological symptoms are present. The pattern of neuropsychological functioning, which can be partially related to the neurophysiological findings, is discussed within the context of existing neuropsychological theories about autistic disorders.
