Abstract
Topoisomerase II alpha (Top II alpha) is a nuclear enzyme that plays a central role in DNA metabolism, and is a molecular target for a variety of chemotherapeutic agents. Top II alpha has recently gained attention as a biomarker for therapy response and patient survival. In this study, we attempted to assess the feasibility of measuring Top II alpha gene expression in RNA, isolated from archival formalin-fixed paraffin-embedded tissue specimens, which are used routinely in pathology laboratories. We have employed a new technique on the basis of magnetic particles' separation and purification of nucleic acids, and evaluated both protein and mRNA expressions from the same routinely processed tissue blocks. We investigated the expression of Top II alpha mRNA and protein by real-time reverse transcription polymerase chain reaction and immunohistochemistry, in a cohort of 133 primary ovarian carcinomas, and evaluated the association between Top II alpha expression and clincopathological variables as well as patient outcome. Elevated Top II alpha mRNA expression was observed in high-grade tumors (P=0.003) and advanced stage disease (P=0.011). In univariate Kaplan-Meier analysis, patients with higher expression of Top II alpha nuclear protein had a significantly decreased overall survival (P=0.045). Interestingly, we detected cytoplasmic protein expression of Top II alpha in a subset of samples. Cytoplasmic expression of Top II alpha was associated with the expression of chromosomal region maintenance/exportin 1 (CRM1)-a nuclear export protein (P=0.008). Our study suggests that Top II alpha overexpression is involved in the progression of ovarian cancer in a subset of the patients. Our results encourage the further evaluation of the prognostic and predictive values of Top II alpha expression in ovarian carcinoma, which might help to assess the patients' risk profile, and the planning of an individualized therapy.