p27/kip1 expression in human astrocytic gliomas.

In the cell cycle, p27/kip1 acts as an inhibitory protein of cyclin-cdk complexes. p27/kip1 immunohistochemistry was performed in 50 gliomas (15 astrocytomas, 15 anaplastic astrocytomas and 20 glioblastomas) by a polyclonal antiserum. In the same tumours, proliferation marker Ki-67 was studied by MIB-1 antibody. For both, a labelling index (LI) was calculated after counting at least 1000 cells at x1000 magnification. p27 is diffusely and strongly expressed in astrocytomas (LI mean = 44.4%), whereas positive nuclei decrease in number and in staining intensity in anaplastic astrocytomas (LI mean = 5.86%) and glioblastomas (LI mean = 2.1%). An inverse correlation has been found between MIB-1 LI and p27 LI calculated in the same areas. Interestingly, in malignant gliomas the absence of p27 was independent from any histological feature of differentiation or anaplasia. p27 expression is thus reduced in malignant gliomas as in other malignancies. Since mutations of p27/kip1 are extremely rare, posttranslational changes are hypothesised also in astrocytic gliomas.