Identification of MG-160, a FGF binding medial Golgi sialoglycoprotein, in brain tumors: an index of malignancy in astrocytomas.

Malignant astrocytomas are highly invasive, vascular neoplasms that comprise the majority of nervous system tumors in humans. A strong association has previously been made between malignancy in human astrocytic tumors and increased expression of certain fibroblast growth factor (FGF) family members. MG-160 is an intrinsic type I cysteine-rich membrane sialoglycoprotein that resides in the medial cisternae of the Golgi apparatus, highly homologous to CFR, chicken fibroblast growth factor receptor, and ESL-1, E-selectin ligand. MG-160 binds fibroblast growth factors (FGFs) and may be involved in the intracellular trafficking of FGFs and the regulation of cellular response to FGFs. In the present study MG-160 expression was evaluated in human brain tumors exhibiting varying degrees of malignancy. At the mRNA level MG-160 expression was inversely correlated with the histological grade of astrocytomas such that high levels of MG-160 were observed in low-grade astrocytomas and low levels in malignant astrocytomas. This differential expression of MG-160 mRNA was verified at the protein level using immunohistochemistry. Grade II astrocytomas displayed consistent and intense staining for MG-160 as seen in normal brain. In contrast to the lower grade tumors, grade IV astrocytomas exhibited variable and weaker expression of MG-160. Our results suggest that, MG-160 may participate in malignant progression in astrocytomas. In addition, other brain tumors and human astrocytoma cell lines were characterized for MG-160 expression.