| Abstract |
Recent evidence suggests an association between up-regulation of beta-catenin/Wnt signaling pathway and neuronal differentiation of neuroblastoma. We overexpressed beta-catenin into a human neuroblastoma cell line NB-1 and observed its effect on cellular morphology, growth potential and alteration in a known differentiation related gene, trkA. Expression plasmids containing wild-type and mutated forms of beta-catenin gene were transfected into NB-1 cells, using liposome-based transfection method. The mutated forms were a deletion of three nucleotides of codon 45 and a large deletion involving the whole exon 3. In the transient transfection model, cell viability assay demonstrated significant negative effect of mutated beta-catenin transfection, but not wild-type, on the cell proliferation. To investigate impacts of beta-catenin overexpression in detail, a stable transfection model was established. Clones with comparable expression of beta-catenin at the mRNA level were selected. Only the selected clones with mutated form of beta-catenin exhibited neurite extension pattern and stunned cell proliferation, in association with higher accumulation of total cellular beta-catenin protein as evidenced by Western blot and immunocytochemistry. Cell cycle progression demonstrated significantly higher G0-G1 fraction in each stable cell clone with beta-catenin expression plasmid. In addition, retarded G1/S transition was observed exclusively in the cell clones with mutated form. Concomitantly with overexpressed beta-catenin, up-regulations of trkA and Ha-ras were also identified. Our study suggests a potential availability of beta-catenin/Wnt signaling pathway as a target of molecular manipulation for treatment of high-risk neuroblastoma and a potential association between the pathway and the trkA/neurotrophin cascades.
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