Cell-cycle inhibitor p27/Kip-1 expression in non-astrocytic and non-oligodendrocytic human nervous system tumors

p27/kip-1 is a 'universal inhibitor' which inhibits cyclin complexes with c yclin-dependent kinases (CDKs), preventing cell cycle from the G1-S progres sion. It is expressed in normal oligodendrocytes and in differentiated glia l tumors, decreasing with anaplasia and malignancy. In non-astrocytic and n on-oligodendrocytic tumors of the nervous system, such as meningiomas, schw annomas, medulloblastomas, neuroblastomas and malignant lymphomas, p27/kip- 1 is inconstantly and sometimes poorly expressed. This can be due to the la cking of p27 expression in the normal counterpart of tumor cells. In some t umors, p27/kip-1 expression can be attributed to a differentiation process, as in the pale islands of desmoplastic medulloblastoma and in neuroblastom as. A correlation of p27/kip-1 expression with histology was not found, wit h the exception of apoptosis in medulloblastomas. p27/kip-1 is in feed-back with cyclins and CDKs for the control of cell proliferation and its expres sion may occur where requested by the interplay with cyclins and other inhi bitors. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.