OBJECTIVE: ABCA2 is a member of the adenosine triphosphate-binding cassette transporter superfamily and is proposed to exert critical functions in the transmembrane transport of endogenous lipids such as myelin. It is expressed predominantly in the cytoplasm of oligodendrocytes and Schwann cells, the myelin-forming cells in the brain and peripheral nerves. Recently, it has been shown that it may be a useful marker for the cellular characterization of vestibular schwannomas.
METHODS: To determine whether or not ABCA2 can distinguish oligodendrogliomas from astrocytic tumors, the authors investigated the expression of ABCA2 in a panel of 55 glioma tissues (13 oligodendrogliomas, nine anaplastic oligodendrogliomas, 12 anaplastic astrocytomas, and 21 glioblastomas) using real-time reverse- transcriptase polymerase chain reaction analysis, immunoblot analysis, and immunohistochemistry analysis. The authors also compared the expression of Olig2, a recently identified marker for oligodendroglioma.
RESULTS: The relative expression level of ABCA2 messenger ribonucleic acid determined by real-time quantitative polymerase chain reaction is significantly higher (by a factor of five) in oligodendroglioma than in anaplastic astrocytoma or glioblastoma. It was moderately increased in anaplastic oligodendrogliomas. In immunohistochemical analysis, ABCA2 exhibited remarkable immunopositivity in 11 out of 13 oligodendrogliomas showing a granular pattern in the cytoplasm of tumor cells. However, ABCA2 was completely negative in most anaplastic astrocytomas (75%) and glioblastomas (76%). Anaplastic oligodendroglioma showed an intermediate pattern: strongly positive in two out of nine samples and negative in seven out of nine samples. However, Olig2 was strongly positive in most anaplastic astrocytomas (83%) and glioblastomas (71%). Although there was no difference in the detection of oligodendroglial tumors, the specificity (negative in astrocytic tumor) was significantly higher in ABCA2 than in Olig2.
CONCLUSION: These lines of evidence suggest that ABCA2 could be a molecular marker for oligodendroglioma.