DNA topoisomerase II alpha and -beta expression in human ovarian cancer

To study DNA topoisomerase II alpha (Topo-II alpha) and -beta expression and regulation in human ovarian cancer, 15 ovarian tumour samples were investigated. To compare different levels of expression, the samples were screened for topo II alpha and -beta mRNA with Northern blotting and a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay for Topo-II alpha mRNA. Additionally. protein levels were determined with Western blotting and topoisomerase II activity levels with the decatenation assay. The results obtained were compared with each other and with the tumour Volume index of the samples. In tumours with a tumour volume index greater than or equal to 50%, the mRNA levels (as determined by Northern blotting) and protein levels for each isozyme were in accordance. Additionally, correlations were found between Topo-II alpha RT-PCR data and Topo-II alpha Northern blot results, and between Topo-II alpha RT-PGR data and Topo-II alpha protein levels. interestingly, Topo-II beta protein levels correlated better with Topo-II activity than Topo-II alpha protein levels. In eight ovarian cystadenoma samples, no Topo-II alpha protein could be found. In only three out of eight of these cystadenomas, Topo-II beta protein could be detected. These findings suggest that Tapo-II alpha and Topo-II beta protein levels are upregulated in ovarian cancer and may indicate that Topo-II beta is an interesting target for chemotherapy in ovarian tumours.