The expression of CMP-NeuAc: Galβ1,4GlcNAc α2,6 sialyltransferase [EC 2.4.99.1] and glycoproteins bearing α2,6-linked sialic acids in human brain tumours

The expression of CMP-NeuAc: Galβ1,4GlcNAc α2,6 sialyltransferase (α2,6-ST) [EC 2.4.99.1] and glycoproteins bearing α2,6-linked sialic acids were examined in primary human brain tumours and cell lines. 79% (19/24) of the meningiomas expressed α2,6-ST mRNA, 42% (10/24) of which showed very high expression. α2,6-ST mRNA expression was undetectable in normal brain tissue. In contrast, only 1/13 of the gliomas examined expressed detectable α2,6-ST mRNA. Metastases to the brain did not express measurable amounts of α2,6-ST mRNA. Less expression was found in malignant (i.e., anaplastic) compared to benign (i.e. meningothelial) meningiomas. Two-dimensional SDS-PAGE of glioma and meningioma proteins, followed by Sambucus nigra lectin staining, revealed the presence of a glycoprotein bearing α2,6-linked sialic acids, M_r=53 kDa and a pI=7.0 (MEN-1) that appeared in all seven of the meningiomas examined, but was expressed at barely detectable levels, if at all, in seven out of the seven glioblastomas examined. Thus, decreased α2,6-ST expression may play a role in the aggressive nature of anaplastic meningiomas, but appears to be virtually absent in all tumours of glial origin.