Experimental Study On The Distinct Diagnostic Significance Of OLIG I To Oligodendroglial Tumors

The most common primary tumors of the human brain are thought to be of glial cell origin. However, glial cell neoplasms cannot be fully classified by cellular morphology or with conventional markers for as-trocytes, oligodendrocytes, or their progenitors, which makes the difficulty for diagnosis of primary cerebral neoplasms, especially the differential diagnosis between astrocytoma and oligodendrocytoma. Recently some scientist has found a new marker--oligodendrocyte lineage gene (OLIG1/2) plays a role in glial development. In the rodent central nervous system, they are expressed exclusively in oligodendrocytes and oligodendrocyte progenitors, and OLIG1 can promote formation of a chondroitin sulfate proteoglycon - positive glial progenitor. Here we show that human OLIG genes are expressed strongly in oligo-dendroglioma, contrasting absent or low expression in astrocytoma.MethodsTotal 30 brain tumor samples were obtained via open neurosurgi-cal resection of masses from 22 patients of neurosurgery ward of 1st affiliated hospital of China Medical University. Each sample was fixedand sectioned to be 3 wax - slices. 2 slices were used for in - situ hybridization, 1 for pathological diagnosis. The reagent and probe are provided by Invitrogen Co. All analyses of expression level were performed at low - power magnification of microscopy, and photos are taken. OLIG gene expression levels were scored from low to strongly positive ( + / - to +++++ ) on a six - grade arbitrary scale, depending on the percentage and intensity of OLIG - positive cells in tumors.Results10 samples in Total 12 oligodendrocytoma samples show strongly positive expression; comparing the low expression in astrocytoma(2 in 12 samples show positive expression), glioblastoma( GBM) and normal cerebral tissue.ConclusionThe oligodendrocytoma and other glioma are different in biological behavior, prognosis after total resection, as well as sensitivity to chemical or radiological therapy. But the histopathological diagnosis is difficult. By the newest WHO classification standard for gliomas, they are still classified by morphology, which is subjective. Cell type -specific marker proteins for mature oligodendroglial cells, such as my-elin basic protein, myelin - associated glycoprotein, myelin proteolip-id protein, 2',3'- cyclic nucleotide -3'- phosphodiesterase, and ga-lactolipids ( GalC, O1, O4) , are not expressed at detectable levels hi oligodendrogliomas. Astrocytic glial cell markers such as glial fibril-lary acidic protein ( GFAP) and S - 100β are expressed in both astro-cytomas and oligodendrogliomas at various levels. They may be very useful for the diagnosis of astrocytomas but not for oligodendrogliomas. The analysis of OLIG expression by in - situ hybridization might be useful and available routinely to improve the diagnosis and the classification of gliomas.