Proliferative activity in human glioblastomas: evaluation of different Ki67 equivalent antibodies

Determination of proliferative activity in human gliomas may be of clinical importance. Immunohistochemical estimation of the proliferative index with the prototypic monoclonal antibody Ki67 is often used but has the disadvantage that it must be carried out on frozen material. However, novel Ki67 equivalent antibodies have been developed for use on formalin fixed and paraffin wax embedded tissue. In this study, the prototypic Ki67 antibody and several new Ki67 equivalent antibodies were tested on human glioblastoma tissue.

Eleven glioblastomas were included in the study. The antibodies used were the prototypic monoclonal Ki67 and the novel Ki67 equivalent antibodies MIB1 (monoclonal), NC-MM1 (monoclonal), NC-Ki67p (polyclonal), and rabbit antihuman Ki67 antigen (polyclonal). The prototypic Ki67 was used on frozen sections and the other Ki67 antibodies on microwave oven heated, formalin fixed and paraffin wax embedded sections.

All antibodies exhibited specific granular nuclear staining of weak to strong intensity. In some tumours the labelling indices were within the same range, whereas in others the antibodies elicited divergent values.

All the novel Ki67 equivalent antibodies provided satisfactory staining on paraffin sections. However, a significant spread of labelling indices was recorded in some cases. Therefore, Ki67 immunostaining is encumbered with some degree of uncertainty and requires further optimisation before it can be regarded as a reliable prognostic marker.