25. Expression of p21 and p27 cell cycle proteins in neoplasms of central nervous system. An immunohistochemical study

The cell cycle proteins p21 and p27 are inhibitors of cyclin-dependent kinase and are negative regulators of progression of G1 phase. Few study have focused on expression of these proteins in CNS tumors. The following series of neoplasms were evaluated: 21 malignant astrocytomas (grade III and IV, WHO), 21 oligodendrogliomas, 2 astrocytomas (grade II, WHO), 4 pilocytic astrocytomas, 2 neurocytomas. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded material using p27 and p21 mouse monoclonal antibodies (Neo Markers). p27 and p21 staining was evaluated semiquantitatively. p27 was expressed in: 5/21 (24%) malignant astrocytomas, 1/2 (50%) astrocytomas, 3/4 (75%) pilocytic astrocytomas, 17/21 (81%) of oligodendrogliomas and 2/2 (100%) neurocitoma. p21 was not significatively expressed in any cases except in 1 out 21 (5%) oligodendrogliomas. Our preliminary results indicate that p27 is significantly expressed in low grade neoplasms. Moreover its high expression in oligodendrogliomas support their distinctive biology from diffuse astrocytomas.