Glioma, the most common
primary brain tumor, is characterized by proliferative-invasive growth. However, the detailed
biological characteristics of invading
glioma cells remain to be elucidated. A
monoclonal antibody (clone HMab-1) that specifically and sensitively recognizes the
isocitrate dehydrogenase-1 (IDH1)
protein carrying the R132H mutation can identify invading
glioma cells by immunostaining. To investigate the degree of invasion in
gliomas of distinct grades and the proliferative capacity of the invading cells, immunofluorescent staining was conducted using
antibodies against IDH1-R132H and Ki-67 on 11 surgical and autopsy specimens of the
tumor core and the invading area. Higher numbers of IDH1-R132H-positive cells in the invading area correlated with a higher
tumor grade. Double staining for IDH1-R132H and Ki-67 demonstrated that most invading cells that expressed IDH1-R132H were not stained by the Ki-67 antibody, and the ratio of Ki-67-positive cells among IDH1-R132H-positive cells was significantly lower in the invasion area than in the
tumor core in all grades of
glioma. These data suggest that higher grade
gliomas have a greater invasive potential and that invading cells possess low proliferative capacity.