Immunocytochemical study of DNA topoisomerase IIα and tumour cell proliferation in non-Hodgkin's lymphomas (NHL)

Abstract

Background DNA topoisomerase II alpha (topo IIα) is an enzyme that functions to separate intertwined chromosomes before mitosis. Topoisomerase IIα also is the molecular target for a variety of clinically useful anticancer drugs. Several of the agents are used to treat in most cases NHLs. To evaluate the potential association between topoisomerase IIα and cell proliferation, ki67 immunostaining was also assessed. Methods Topoisomerase IIα (topo IIα) and the monoclonal antibody MIB1 (ki67) were investigated immunocytochemically on imprints smears obtained from 30 patients aged from 22 to 82 years (mean age 45.3) with NHLs. The study comprised 16 patients with high-grade and 14 with low-grade NHLs. The cytomorphological diagnoses were verified by histology and were classified according to Kiel classification. We use the avidin-biotin streptavidin immunoperoxidase technique and the monoclonal antibodies topoisomerase IIα (Clone 3F6 YLEM dilution 1:20) and the MIB1 (ki67 YLEM ready to use). Results The average topo IIα index of high-grade NHLs was 50 with range from 15.2 to 78.5 whereas the average topo index of low-grade NHL was 10 with a range from 0.8 to 15. The average of ki67 index of high-grade was 50.1 with range 45–80 while the average of low-grade NHl was 13.6 with a range from 2.5–78.9. Statistical analysis was employed by Mann–Whitey U-test and the two values for high and low grades are statistically significant (P < 0.001). Conclusions These results show that high-grade NHLs have topo IIα and MIB1 indices that are significantly higher than low-grade NHLs. The ratio of expression compatible with the grade of malignancy in NHLs possibly identifies the cases which are more or less sensitive to chemotherapy agents.