Cystatin C and transthyretin expression in normal and neoplastic tissues of the human brain and pituitary

The localization of cystatin C (CC) and transthyretin (TTR) synthesis was studied using Northern blot and immunohistochemical methods. Normal brain tissues from all sites studied contained CC mRNA. Immunoreactive CC was present in the choroid plexus epithelial cells, cerebral and cerebellar neurons, astrocytes, ependymal cells, macrophage-like cells of the arachnoid membrane and in neuroendocrine cells of the anterior pituitary lobe. TTR mRNA and TTR were restricted to the choroid plexus. In primary brain tumors, the transcript for CC was found in all 39 tumors examined, while the protein could only be demonstrated in 3/5 choroid plexus papillomas, 8/8 astrocytomas, 7/23 anaplastic astrocytomas and glioblastomas, 1/6 oligodendrogliomas, 1/1 oligoastrocytoma, 1/4 anaplastic oligodendrogliomas, 3/7 ependymomas, 0/1 anaplastic ependymoma, 0/5 primitive neuroectodermal tumors, 0/1 neuroblastoma, 3/11 meningiomas and 16/16 pituitary adenomas. CC cannot be used as a marker for any specific brain tumor type but the fact that the protein could be demonstrated more frequently in astrocytomas than in their more malignant counterparts suggests that the cellular production and secretion of CC changes with the malignant progression of these tumors. TTR mRNA and TTR were present only in the choroid plexus papillomas, indicating that TTR synthesis is mainly restricted to such brain neoplasms.