Expression of cell proliferation markers in pituitary adenomas – correlation and clinical relevance of MIB-1 and anti-topoisomerase-IIα

Summary

Pituitary adenomas represent an inhomogenous tumor entity in terms of growth rate, invasiveness and recurrence. To improve understanding of their different biological behaviour, tumor cell proliferation markers are applied. The aim of this study was to assess proliferation rates overall and in clinico-pathological subgroups using MIB-1 and the recently introduced cell proliferation marker anti-topoisomerase-IIα (Topo-IIα). Further, we correlated the two markers, and defined the clinical value of Topo-IIα in pituitary adenomas as compared to MIB-1.

We analyzed tumor cell proliferation rates using MIB-1 and Topo-IIα antibodies on samples of 260 primary pituitary adenomas. We excluded recurrent cases and cases with drug pretreatment. Median patient age at the time of surgery was 47 years (range 14–86 years), the male:female ratio was 1:1. The total cohort comprised 110 non-functioning and 150 functioning cases. Subtyping was performed according to hormonal expression as defined by WHO. Tumor size and invasiveness were noted from surgical and/or radio logical reports in 95% of cases.

Overall MIB-1 index was median 1.8% (range 0.2–23.6%), Topo-IIα index was median 1.0% (range 0–14.4%) with a strong correlation between the two markers (R=0.837, P<0.001). As compared to MIB-1, mean Topo-IIα values were significantly lower by a factor 1.8. Only MIB-1 was significantly higher in invasive as compared to non-invasive adenomas, in tumors ≤3 cm in diameter, and in the age-group 21–40. Female gender had significantly higher MIB-1 and Topo-IIα indices than male. Silent ACTH-cell and PRL-producing adenomas had the highest, null-cell adenomas and gonadotropinomas the lowest proliferation values, respectively.

Our data show a strong correlation between MIB-1 and Topo-IIα indices in pituitary adenomas. Only MIB-1 but not Topo-IIα demonstrated significantly higher values in invasive adenomas. Therefore, MIB-1 seems more useful than Topo-IIα for decisions regarding postoperative patient management.