Malignant Transformation of Cultured Low Grade Glioma Cells: An Immunohistochemical and Ultrastructural Study

Using cultured glioma cell line, we demonstrated in vitro and in vivo that when low grade glioma was pass through glioma cell culture at 19th passage, these tumor cells were malignantly transformed. This cell line was established from tissue culture of neurosurgical specimen, pathologically diagnosed as glioma (low grade glioma; grade 1-11) with glial fibrillary acidic protein (GFAP) positive but vimentin negative. When glioma cell cultured at 19th passage was injected into xenograft nude mice, histopathological and immunohistochemical analysis demonstrated that low grade glioma cells were transformed to high grade glioma (grade IV). High grade glioma cell can produce vimentin, laminin and fibronectin, but can not produce GFAP. It is suggested that vimentin and GFAP are useful and important marker in differentiating low grade glioma from high grade glioma. The mechanism of malignant transformation of low grade glioma cells is not clear. The possible explanation may be that the low grade glioma gene include malignant potential originally, as a result, low grade glioma cells change gradually to high grade glioma. of cells to a substrate and junction of morphological changes and cell differentiation," and neurite outgrowth."' Vimentin is expressed in poorly differentiated astrocytoma, but not in well differentiated astrocytoma. On the other hand, glial fibrillary acidic protein (GFAP) is demonstrated in well differentiated astrocytoma, but not in pooly differentiated astrocytoma.20' Vimentin and GFAP are considered to be important markes of differentiation of astro-cytoma.11,12, 15) The authors reported here a new finding that demonstrated in vitro and in vivo, low grade glioma when pass through glioma cells culture at 19th passage and injected into xenograft nude mice, histopathological and immuno-histochemical analysis showed that the tumor cells were malignantly transformed.