Metallothionein overexpression in human brain tumours

Metallothioneins (MTs) are metal binding proteins overexpressed in various human neoplasms which are associated with resistance to cytotoxic drugs. A series of 156 archival human brain tumours were investigated immunohistochemically for expression of MTs; these included 10 low-grade gliomas, 44 high-grade gliomas, 98 meningeal tumours (19 classical, 30 atypical, 38 anaplastic meningiomas, and 11 haemangiopericytomas or papillary meningiomas), and 4 other tumours. Low-grade gliomas showed heterogeneous MT expression; 32 high-grade gliomas (72.7%) showed MT expression of more than 25% of tumour cells without statistically significant differences between first operations and recurrent tumours. In 2 glioblastomas, the presence of MT was confirmed by Western blotting. The extent of MT immunoexpression showed a statistically significant inverse relationship to the degree of p53 immunoreactivity. In meningiomas, a tendency to a higher percentage of MT-expressing cells was observed from classical over atypical to anaplastic meningiomas, but these differences were not statistically significant. In conclusion, MT expression is present in a significant portion of, especially malignant, brain tumours and might be involved in their poor response to antineoplastic drugs.