Differential expression of versican isoforms in brain tumors

Abstract

Versican is a member of the family of large aggregating chondroitin sulfate proteoglycans which are one of the major constituents of brain extracellular matrix (ECM). We examined the expression of versican splice variants at mRNA and protein levels in normal human brain and in gliomas, medulloblastomas, schwannomas, neurofibromas, and meningiomas. RT-PCR revealed transcripts for V0 and V1 in all tissues. V2 mRNA was restricted to gliomas and normal brain, while V3 mRNA was detected in all tissues except for medulloblastomas. Immunohistochemistry using antibodies to the glycosaminoglycan (GAG)-α attachment domain of versican (present in V0 and V2) revealed decreased staining of most glioma ECMs compared to normal neuropil, while some abnormal tumor vessels, but not normal cerebral vessels, were GAG-α-positive. Expression of the GAG-β attachment domain (present in V0 and V1) was faint in normal neuropil and cerebral vessels, but increased in tumor vessels and was absent in most glioma ECMs. Both GAG-α and GAG-β were expressed in connective tissue of all nonglial tumors. Our data suggest that V2 is the major versican isoform of normal neuropil and glioma ECM. Furthermore, increased expression in tumor vessels and decreased expression in glioma ECM of the anti-adhesive versican may be related to marked local invasivity and rarity of extracranial metastasis of gliomas.