Galectin-3 in preneoplastic lesions of glioma

Gliomas are the most common primary brain tumors in adults and have a poor prognosis. Galectin-3 is a β-galactosidase-binding lectin which is important in pre-mRNA splicing, regulation of cell proliferation, cell adhesion and apoptosis. Although galectin-3 has been shown as a glioma related marker and expression of galectin-3 has been reported to correlate with WHO grade in human gliomas, expression of galectin-3 in early neoplastic lesions such as early neoplastic proliferation (ENP) and microtumor is still far from fully understood. In the present study, expression of galectin-3 in ethylnitrosourea-induced rat gliomas including preneoplastic and neoplastic lesions was examined by immunohistochemistry for galectin-3, Iba-1 (a specific microglial cell marker), GFAP (a specific astrocyte cell marker), and conventional hematoxylin and eosin staining (for morphological observation). The results showed that exact location of ENP was detected clearly by galectin-3 immunohistochemistry whereas normal brain tissues were negative. In ENP and microtumor, galectin-3 was expressed in neoplastic astrocytic cells but rarely in microglia. In malignant glioma, however, galectin-3 was expressed in both neoplastic astrocytic cells and microglia. This suggests that galectin-3 is activated in microglia and macrophages according to the progression of glioma. Galectin-3 was not expressed in oligodendrocytic cells. Our results indicate that galectin-3 is a good specific marker indicating the early stage of glioma tumorigenesis.