Retinoic Acid Induced Differentiation Of Neuroblastoma Proteomics Research

Neuroblastoma is one of the most common malignancies in childhood, and is also one of the most difficult to treat. As an embryonic tumor, it originates from undifferentiated neuroectodermal cells derived from neuronal crest. Enigmatically neuroblastoma has the highest rate of spontaneous regression among human tumors, and foreign reagents can also induce neuroblastoma differentiation. Neuroblastoma cell lines are good models for neuronal development, through the studies on which molecular mechanism behind neuronal differentiation can be discovered. Differentiation therapy is fascinating to clinicians too.One of the most potent differentiation inducers is retinoic acid. Treatment of neuroblastoma cell lines with all-trans retinoic acid causes significant proliferation inhibition and sometimes neurite outgrowth. Now it is well accepted that most, if not all, of the action of retinoic acid is due to its ability to alter gene expression. Many studies have examined the roles of specific gene products in neuronal differentiation, from which it has been known that multiple biochemical events are involved in neuronal differentiation. However, alteration in the expression of many other genes must be associated with neuronal differentiation. Microarray technology allows relatively rapid and simultaneous identification, comparison, and analysis of thousands of genes. But the transcriptional activity of a given gene is not always in accordance with the expression level of the encoded protein. In a large-scale study of yeast cells it was determined that the correlation coefficient between the amount of an mRNA and the abundance of the corresponding protein to be only about 0.4. Thorough understanding of neuronal differentiation induced by ATRA thus requires direct determination of the accompanying changes in protein level.We therefore used 2D gel strategy to discover proteome alteration of SH-SY5Y cells associated with the differentiation induced by retinoic acid. Between the gels before and after treatment with retinoic acid, 73 differentially expressed protein spots were discovered, among which the expression level of 51 protein spots decreased and that of 22 protein spots increased. Then mass spectrometry was employed to identify differentially expressed proteins. 31 proteins of decreased expression and 9 proteins of increased expression were identified. From analysis of identification results, neuronal differentiation relates to energy metabolism, membrane trafficking, mRNA synthesis, protein synthesis, signal transduction and oncogenes. Expression profile changes accompany differentiation process, in which...