Galectins are differentially expressed in supratentorial pilocytic astrocytomas, astrocytomas, anaplastic astrocytomas and glioblastomas, and significantly modulate tumor astrocyte migration

Galectins, a family of mammalian lectins with specificity to beta -galactos ides, are involved in growth-regulatory mechanisms and cell adhesion. A rel ationship is assumed to exist between the levels of expression of galectins and the revel of malignancy in human gliomas. A comparative study of this aspect in the same series of clinical samples is required to prove this hyp othesis. Using computer-assisted microscopy, we quantitatively characterize d by immunohistochemistry the levels of expression of galectins-1, -3 and - 8 in 116 human astrocytic tumors of grades I to IV. Extent of transcription of galectins-1, -3, and -8 genes was investigated in 8 human glioblastoma cell lines by means of RT-PCR techniques. Three of these cell lines were gr afted into the brains of nude mice in order to characterize in vivo the gal ectins-1, -3 and -8 expression in relation to the patterns of the tumor inv asion of the brain. The role of galectin-1, -3 and -8 in tumor astrocyte mi gration was quantitatively determined in vitro by means of computer-assiste d phase-contrast videomicroscopy. The data indicate that the levels of gale ctin-1 and galectin-3 expression significantly change during the progressio n of malignancy in human astrocytic tumors, while that of galectin-8 remain s unchanged. These three galectins are involved in tumor astrocyte invasion of the brain parenchyma since their levels of expression are higher in the invasive parts of xenografted glioblastomas than in their less invasive pa rts. Galectin-3, galectin-1, and to a lesser extent galectin-8, markedly st imulate glioblastoma cell migration in vitro. Since bands for the transcrip ts of human galectins-2, -4 and -9 were apparently less frequent and intens e in the 8 human glioblastoma cell lines, this system provides an excellent model to assign defined roles to individual galectins and delineate overla pping and distinct functional aspects.