Supratentorial pilocytic astrocytomas, astrocytomas, anaplastic astrocytomas and glioblastomas are characterized by a differential expression of S100proteins

The levels of expression of the S100A1, S100A2, S100A3, S100A4, S100A5, S10 0A6 and S100B proteins were immunohistochemically assayed and quantitativel y determined in a series of 95 astrocytic tumors including 26 World Health Organization (WHO) grade I (pilocytic astrocytomas), 23 WHO grade II (astro cytomas), 25 WHO grade III (anaplastic astrocytomas) and 21 WHO grade IV (g lioblastomas) cases. The level of the immunohistochemical expression of the S100 proteins was quantitatively determined in the solid tumor tissue (tum or mass). In addition twenty blood vessel walls and their corresponding per ivascular tumor astrocytes were also immunohistochemically assayed for 10 c ases chosen at random from each of the four histopathological groups. The d ata showed modifications in the level of S100A3 protein expression; these m odifications clearly identified the pilocytic astrocytomas from WHO grade I i-IV astrocytic tumors as a distinct biological group. Modifications in the level of S100A6 protein expression enabled a clear distinction to be made between low (WHO grade I and II) and high (WHO grade III and IV) grade astr ocytic tumors. Very significant modifications occurred in the level of S100 A1 protein expression (and, to a lesser extent, in their of the S100A4 and S100B proteins) in relation to the increasing levels of malignancy. While t he S100A5 protein was significantly expressed in all the astrocytic tumors (but without any significant modifications in the levels of malignancy), th e S100A2 protein was never expressed in these tumors. These data thus indic ate that several S100 proteins play major biological roles in human astrocy tic tumors.