Isoform-specific expression of 14-3-3 proteins in human astrocytoma

BACKGROUND: 14-3-3 protein plays crucial roles in tumorigenesis, including the maintenance of cell cycle and DNA repair, the prevention of apoptosis, among others. In mammalian cells, seven 14-3-3 isoforms (beta, epsilon, zeta, eta, theta, gamma and sigma) have been identified and each of these seems to have distinct tissue localizations and isoform-specific functions. In the present study, the levels of all seven 14-3-3 isoforms were examined in astrocytoma. METHODS: The expression of 14-3-3 isoforms and their protein expression levels were examined in five glioma cell lines by western blotting. Then in astrocytoma tissues, we investigated expression percentages of each isoform by immunohistochemistry. The protein and mRNA expression levels of each isoform were also detected by western blotting and RT-PCR, respectively. RESULTS: 14-3-3beta and eta were specifically expressed in astrocytoma, and their expression frequencies and levels increased with the increase of astrocytoma malignancy. The result from glioma cell lines was consistent with that from astrocytoma tissue. CONCLUSIONS: In our study, we found two tumor-specific isoforms of 14-3-3 in astrocytoma. They might be involved in astrocytoma tumorigenesis and may be useful as targets for therapy.