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

To study DNA topoisomerase II alpha (Topo-II alpha) and -beta expression an d regulation in human ovarian cancer, 15 ovarian tumour samples were invest igated. To compare different levels of expression, the samples were screene d for topo II alpha and -beta mRNA with Northern blotting and a quantitativ e reverse transcriptase polymerase chain reaction (RT-PCR) assay for Topo-I I alpha mRNA. Additionally. protein levels were determined with Western blo tting 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 pro tein levels for each isozyme were in accordance. Additionally, correlations were found between Topo-II alpha RT-PCR data and Topo-II alpha Northern bl ot 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 cystad enoma samples, no Topo-II alpha protein could be found. In only three out o f eight of these cystadenomas, Topo-II beta protein could be detected. Thes e findings suggest that Tapo-II alpha and Topo-II beta protein levels are u pregulated in ovarian cancer and may indicate that Topo-II beta is an inter esting target for chemotherapy in ovarian tumours.