| Invasive glioma is a common malignant primary brain tumor and carries poor clinical prognosis in both adults and children, but effective therapy is limited by its resistance to conventional therapies. Till now, the mainstay of treatment is surgical debulking and radiotherapy. Although some patients receive multidisciplinary treatments, the median survival of patients with glioblastomas, the most malignant type of astrocytoma, is only one year. Glioma development occurs by means of a series of dynamic changes in the genome that confer growth advantages to transformed cells. Therefore, it is essential for us to find specific tumor markers in tumorigenesis and progression, and understand the molecular mechanisms of astrocytoma, to design more effective therapeutic strategies.14-3-3 protein is a family of highly conserved regulatory molecules, and received its name in 1967 during a systematic classification of brain proteins that was based on their fraction number on anion-exchange chromatography and migration position in gel electrophoresis. It is expressed in all eukaryotic cells and its multiple isoforms have been found in different tissues. In mammals, seven isoforms namedβ,γ,ε,η,θ/τ,σandζhave been identified. Up to now, over 200 14-3-3-binding ligands are identified, and the number of 14-3-3 binding partners is still increasing. Considering the number of binding partners, it is not surprising that 14-3-3 proteins play crucial roles in regulating multiple cellular processes–the regulation of cell differentiation, proliferation, transformation, signal transduction, cell cycle control, vesicular transport, DNA replication and apoptosis. Our previous study has shown that the expression level of 14-3-3 protein was higher in human astrocytoma compared with astrocytes in normal brain tissue. Up to now, no information on whether the elevated level of 14-3-3 protein is due to a specific isoform(s) in astrocytoma. In this study, we addressed this issue from the following aspects.1. The expression of 14-3-3 isoforms in gliomas: The expression of 14-3-3 isoforms was detected by Western blotting in five glioma cell lines (U251MG, U87MG, BT325, SHG44, and U118), one astrocytic cell line SVGp12, 24 cases of frozen tumor tissue from patients with glioma, and 10 normal human brain tissue samples. The results showed that, 14-3-3βandηwere only expressed in five glioma cell line and glioma tissue and their expression level rised with improving pathological grades of gliomas(P<0.05). 14-3-3θ,εandζwere expressed both in glioma tissue, normal brain tissue and astrocytic cell line. The relative expression levels of 14-3-3εandζrised with improving pathological grades of gliomas(P<0.05). The relative expression level of 14-3-3θwas not obviously different in various grades of astrocytoma (P>0.05), but higher than that in normal brain tissue (P<0.05). 14-3-3γandσwere not detected in all the tissue and five cell lines.2.The expression of 14-3-3βmRNA in gliomas: 14-3-3βmRNA level was detected by RT-PCR in 24 cases of frozen tumor tissue from patients with glioma and 5 normal brain tissue samples. The results indicated that, 14-3-3βmRNA was only expressed in astrocytoma, and its expression level showed positive trends with tumor malignancy grading (P<0.05).3.The expression of 14-3-3βprotein in glioma cell line: The expression of 14-3-3βisoform was detected in normal astrocytic cell line SVGp12 and glioma cell line U251 by immunocytochemical ABC method. The results showed that, 14-3-3βisoform immunoreactivity was observed only in glioma cell line U251MG, but not in normal astrocytic cell line SVGp12.In summary, no matter in cell or tissue, at mRNA level or protein level, 14-3-3βwas only expressed in glioma cell line and glioma tissue, and its expression level showed postive trend with glioma malignant grading. At the first time, this study suggested that 14-3-3βmight be a key protein in initiation and progress of human brain glioma. Therefore, 14-3-3βmight act as an ideal target for gene therapy of astrocytoma.
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