Overexpression of cyclin A and cyclin B1 proteins in astrocytomas

Background.-Cyclins are proteins that are expressed during the progression of a normal cell through the cell cycle. In a number of cancers, overexpres sion of cyclin A and cyclin B1 proteins has been reported, and In some inst ances the levels of expression correlated well with the grades of malignanc y. The expression of cyclin A and cyclin B1 proteins in astrocytoma may be linked to the histologic grade or proliferative activities. Objective.-To study the expression of cyclin A and cyclin B1 proteins in as trocytomas and correlate the labeling indices (LIs) of cyclin A and cyclin B1 with histologic grade and Ki-67 LI. Design.-The surgical biopsy specimens from 65 adults with astrocytomas were reviewed and divided into grades based on the World Health Organization sy stem. The paraffin sections were immunostained using primary antibodies aga inst Ki-67, cyclin A, and cyclin B1. The LIs of these astrocytomas for the 3 different antibodies were determined by computerized image analysis. Results.-The cyclin A LI showed good correlation with astrocytoma grade and Ki-67 LI. Both the nuclear and cytoplasmic cyclin B LIs correlated well wi th the tumor grade but showed poor correlation with Ki-67 LI. Conclusions.-This study suggests that although both cyclin A and B protein expression are related to the grade of malignancy in astrocytomas, cyclin A levels more generally reflect the proliferative state of these tumors. We also provide indirect evidence that cyclin B1 is associated with the aberra nt progression through the G2-M phase checkpoint in astrocytomas.