Evaluation of DNA topoisomerase IIα expression provides independent prognostic information in non‐Hodgkin's lymphomas

Abstract

AIMS: In view of the dual role that DNA topoisomerase IIa (TopoIIa) plays as a cell proliferation marker and as a possible indicator of chemosensitivity, we investigated its expression in non-Hodgkin's lymphomas (NHL) in relation to conventional clinicopathological parameters, cell proliferation (as defined by Ki67 immunoreactivity), response to therapy and patient outcome. METHODS AND RESULTS: Formalin-fixed paraffin-embedded tissues from 153 patients with NHL were immunohistochemically stained for TopoIIalpha. Patients were followed up until death (n = 63) or for an average of 68 months (median 64 months, n = 90). The percentage of TopoIIalpha positive cells (TopoIIalpha LI) increased with grade (P < 0.001), extranodal location (P = 0.05) and Ki67 LI (P = 0.01, r = 0.673). In most cases (58%), Ki67 LI exceeded TopoIIalpha LI (TopoIIalpha/Ki67 < 1), especially within the indolent group (P < 0.001). TopoIIalphaLI, Ki67LI and TopoIIalpha/Ki67 ratio were all adversely related to overall survival in univariate analysis, though their significance was not maintained after adjustment for grade. In multivariate analysis high TopoIIalpha/Ki67 ratio and high TopoIIalpha LI independently predicted shortened overall and post-relapse survival, respectively. Most importantly, low TopoIIalpha/Ki67 ratio was the only independent predictor of diminished disease-free survival. However, there was no relationship between TopoIIalpha expression and response. CONCLUSIONS: Our results suggest that evaluation of TopoIIalpha expression and TopoIIalpha/Ki67 ratio as cell proliferation markers provides independent prognostic information in relation to post-relapse and overall survival. Furthermore, TopoIIalpha/Ki67 ratio appears to play a key role in the identification of patients prone to early relapse.