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DNA topoisomerase IIalpha and -beta expression in human ovarian cancer
S Withoff1, A G van der Zee, S de Jong
1Division of Medical Oncology, University Hospital Groningen, The Netherlands.
Abstract:
To study DNA topoisomerase IIalpha (Topo-IIalpha) 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 IIalpha and -beta mRNA with Northern blotting and a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay for Topo-IIalpha 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 > or = 50%, the mRNA levels (as determined by Northern blotting) and protein levels for each isozyme were in accordance. Additionally, correlations were found between Topo-IIalpha RT-PCR data and Topo-IIalpha Northern blot results, and between Topo-IIalpha RT-PCR data and Topo-IIalpha protein levels. Interestingly, Topo-IIbeta protein levels correlated better with Topo-II activity than Topo-IIalpha protein levels. In eight ovarian cystadenoma samples, no Topo-IIalpha protein could be found. In only three out of eight of these cystadenomas, Topo-IIbeta protein could be detected. These findings suggest that Topo-IIalpha and Topo-IIbeta protein levels are up-regulated in ovarian cancer and may indicate that Topo-IIbeta is an interesting target for chemotherapy in ovarian tumours.
Insights
DNA topoisomerase IIalpha and IIbeta proteins are elevated in ovarian tumors, suggesting Topoisomerase IIbeta may be a promising target for ovarian cancer chemotherapy.
Area of Science:
- Molecular Biology
- Oncology
Background:
- DNA topoisomerases are crucial enzymes involved in DNA replication and transcription.
- Topoisomerase IIalpha (Topo-IIalpha) and Topoisomerase IIbeta (Topo-IIbeta) are two main isoforms with distinct roles.
Purpose of the Study:
- To investigate the expression and regulation of Topo-IIalpha and Topo-IIbeta in human ovarian cancer.
- To compare enzyme levels with tumor characteristics and assess their potential as therapeutic targets.
Main Methods:
- Analysis of 15 ovarian tumor samples and 8 cystadenomas.
- Gene expression analysis using Northern blotting and quantitative RT-PCR.
- Protein level assessment via Western blotting.
- Enzyme activity determination using the decatenation assay.
Main Results:
- Topo-IIalpha and Topo-IIbeta mRNA and protein levels were upregulated in ovarian tumors compared to cystadenomas.
- Strong correlations were observed between different methods for assessing Topo-IIalpha expression.
- Topo-IIbeta protein levels showed a better correlation with enzyme activity than Topo-IIalpha.
Conclusions:
- Ovarian cancers exhibit increased levels of both Topo-IIalpha and Topo-IIbeta.
- Topo-IIbeta may represent a valuable therapeutic target for ovarian tumors due to its correlation with enzyme activity.