Galectin-3: cellular distribution and correlation with WHO-grade in human gliomas

In order to elucidate the reason for conflicting results that have been published previously on galectin-3 expression in human gliomas, we used single labeling and double labeling immunohistochemistry experiments to identify cellular origin and extent of galectin-3 positivity in 53 glioma-samples (16 glioblastomas, 21 anaplastic astrocytomas, 16 low-grade astrocytomas). Galectin-3 positivity was observed in neoplastic astrocytes, macrophages/microglial cells. endothelial cells and some B- and T-lymphocytes. The quantitative analysis showed that the percentage of galectin-3 positive cells was significantly higher in the tumor parenchyma of glioblastomas than in anaplastic (p = 0.0371) and low-grade astrocytomas (p = 0.0042). Single labeling with anti-CD68 antibodies revealed a significant correlation between CD68 and galectin-3 immunoreactivity (p = 0.0092). Endothelial cells were labeled in all low-grade and anaplastic astrocytomas, but only in 10/16 glioblastomas (p = 0.0003). This detailed analysis demonstrates that galectin-3 positivity in human gliomas is considerably influenced by tumor-infiltrating macrophages. The differential expression on endothelial cells raises the question if galectin-3 plays a role in tumor angiogenesis of human gliomas.