Caracterização funcional de genes diferencialmente regulados por glicocorticóides e análise do proteoma em linhagem de glioma sensível à hormônios anti-tumorais glicocorticóides / Functional characterization of glucocorticoid differentially regulated genes and proteomic analysis of the anti-tumoral effect of glucocorticoid in a glucocorticoid-sensitive rat glioma cell line

AUTOR(ES)

Marcos Angelo Almeida Demasi

DATA DE PUBLICAÇÃO

2005

RESUMO

The glucocorticoid (GC) growth suppression response is controlled through cellular cascades in which the transcription of primary response genes regulates the expression and activity of a diverse set of genes including important factors for cell cycle progression. However, the functional connection between the GC-regulated transcriptional events and cell cycle arrest of determined cells is poorly understood at the molecular level. In this context, our lab has isolated the ST1 variant of the C6 rat glioma cell line to study the mechanism of action of GC as anti-tumor agents. GC treatment leads ST1 cells to a dramatic tumoral to normal phenotypic reversion, characterized by inhibition of their growth rate in monolayer, loss of their ability to form colonies in semi-solid medium and to induce tumor formation in nude mice, and morphological changes (flattening). As part of the strategy to understand the anti-tumor action of GC, differentially represented proteins, associated with the phenotypic reversion displayed by ST1 cells have been isolated through mRNA-based blind cDNA cloning and, more recently, by two dimensional electrophoresis (2D-PAGE). The sequences isolated by these two methodologies are potential targets for functional analysis. In the present study, we aimed at a) identifying genes which are differentially expressed during the GC-induced phenotypic reversion of ST1 cells, using the proteomic approach (2D-PAGE and mass spectrometry) and b) determining the functional role of a gene (Cyclin G) which had previously being identified as being induced during GC-treatment of the ST1 cells. The analytical methodology used relied on the comparison of sets of 2D nuclear protein profiles of ST1 cells, maintained in the absence (control) and in the presence of GC for 5 and 24h. After image analysis and visual validation, 33 polypeptides were considered as differentially represented 5 h after treatment, 16 of which were also differentially represented after 24 h. Six of those polypeptides were identified by peptide mass fingerprinting (PMF). Evidence obtained by Western blot analysis indicates that one of those polypeptides, Annexin 2 (ANX2), has its sub-cellular location modulated by GC-treatment of ST1 cells. The role of Cyclin G in the tumoral to normal phenotypic reversion induced by GC in ST1 cells was analyzed by over-expression of Cyclin G using a retroviral system and evaluation of the effects of this over-expression over ST1 cells response to GC, by growth curve and flow cytometry assays. The data suggest that Cyclin G over-expression leads to a more intense and prolonged effect of GC on ST1 cells.

ASSUNTO(S)

ciclina g proteomic analyis análise proteômica cellular proliferation hormônios glicocorticóides cyclin g genes - análise funcional proliferação celular genes - functional analysis glucocorticoid hormones

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