Differential Expression of the Tight Junction Protein, Occludin, in Brain Tumors

ABSTRACT

OBJECTIVE: Cerebral edema develops in the brain tumors by loosening of the endothelial tight junction. Tight junction(TJ) proteins, such as occludin and claudin bind adjacent cells tightly. Authors examine the expression rate of occludin in human brain tumors to evaluate the effect of altered expression of occludin on cerebral edema. METHODS: Seventy surgical specimens stored at -70degrees C were used. It included 14 astrocytic tumors, 27 meningiomas, 12 scwannomas, 7 pituitary adenomas, 6 hemangioblastomas, and 4 craniopharyngiomas. After protein extraction, expression of occludin was investigated by Western blot analysis. The tumors were classified according to World Health Organization(WHO) classification. RESULTS: The expression rates of occludin in brain tumors were glioma (8/14=57.1%), meningioma (16/27=59.3%), schwannoma (10/12=83.3%), pituitary adenoma (6/7=85.7%), hemangioblastoma (6/6=100%), and craniopharyngioma (3/4=75.0%). The expression rate in glioma and meningioma was lower than other brain tumors. In gliomas, high grade tumor (1/4=25.0%) exhibited lower expression rate of occludin than low grade one (7/10=70.0%). CONCLUSION: These results suggest that the expression of occludin is different among the various kinds of brain tumors. In gliomas, its expression is correlated with the histological grade. It may indicate that occludin plays a role in the development of edema in the brain tumors.