Topoisomerase IIalpha expression in mantle cell lymphoma: a marker of cell proliferation and a prognostic factor for clinical outcome.

Mantle cell lymphoma (MCL) is a malignant lymphoma associated with a relatively aggressive clinical course and a median overall survival time of 3-4 years. Treatment usually consists of combination chemotherapy, often including topoisomerase (topo) inhibitors such as doxorubicin, etoposide and mitoxantrone. Topo IIalpha is an enzyme that is needed whenever uncoiling of DNA is necessary during the cell cycle. The enzyme is a marker of cell proliferation. We analyzed the expression of topo IIalpha in relation to Ki-67 and the clinical outcome in patients with MCL. Biopsy specimens from 95 untreated patients enrolled in two multicenter trials (1975-1985) were investigated immunohistochemically with monoclonal antibodies against topo IIalpha (Ki-S4) and Ki-67 (Ki-S5). Patients with low (0-10%) topo IIalpha expression had a median overall survival time of 49.0 months, compared to 17.0 months for patients with high (more than 10%) topo IIalpha expression. The Kaplan-Meier analysis showed a significant difference in the overall survival time related to the percentage of topo IIalpha (P<0.001) and Ki-67 (P<0.001) positive tumor cells. Multivariate Cox regression analysis revealed the expression of topo IIalpha as the most important prognostic factor (P<0.001) in MCL superior to the international prognostic index (IPI), the Ki-67 index and other clinical characteristics.