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Human DNA topoisomerase I: An anticancer drug target present in human sarcomas
Landon W Coleman1, L Ralph Rohr, Igor B Bronstein
1Department of Pathology, University of Utah Health Sciences Center, Salt Lake City 84132, USA.
Abstract:
New anticancer drugs targeting DNA topoisomerase I (topo I) are showing activity against human sarcomas. Laboratory studies have indicated that cells responsive to topo I-targeted drugs have elevated levels of topo I, require active DNA replication, and may require a functional apoptotic pathway. In this study, we evaluated these potential markers of topo I-targeted drug sensitivity in 55 cases of human sarcoma (42 high grade, 4 intermediate grade, and 9 low grade). By immunohistochemical staining, we observed elevated topo I expression in 20 of 55 neoplasms (36%). Immunohistochemical staining for the proliferation marker DNA topoisomerase II-alpha (topo II-alpha), showed that 15 of 55 neoplasms (27%) had topo II-alpha indices >50, indicating a large number of actively cycling tumor cells. Abnormal p53 expression was observed in 19 of the 55 cases (35%). None of the cases were interpreted as positive for ALK-1. To complement our immunohistochemical staining of topo I, we isolated functionally active topo I from extracts of a human sarcoma. These isolates demonstrated that sarcoma topo I is sensitive to topo I-targeted anticancer drugs. Of the 55 cases of human sarcoma, 7 (13%) had high levels of topo I, a large number of cycling tumor cells, and normal p53 expression. These are the molecular parameters that might suggest responsiveness to drugs targeting topo I.
Insights
New research identifies key markers for predicting human sarcoma response to DNA topoisomerase I (topo I) targeted anticancer drugs. High topo I levels, active DNA replication, and normal p53 indicate potential drug sensitivity.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Research
Background:
- Anticancer drugs targeting DNA topoisomerase I (topo I) show promise against human sarcomas.
- Drug sensitivity in cancer cells is linked to elevated topo I, active DNA replication, and functional apoptosis.
Purpose of the Study:
- To evaluate potential markers of topo I-targeted drug sensitivity in human sarcoma.
- To correlate specific molecular profiles with potential drug responsiveness.
Main Methods:
- Immunohistochemical staining was used to assess topo I, DNA topoisomerase II-alpha (topo II-alpha), and p53 expression in 55 human sarcoma cases.
- Functional activity and drug sensitivity of isolated sarcoma topo I were tested.
- Proliferation was assessed via topo II-alpha indices.
Main Results:
- Elevated topo I expression was found in 36% of sarcomas.
- 27% of tumors exhibited high proliferation rates (topo II-alpha index >50).
- Abnormal p53 expression was observed in 35% of cases.
- A subset of 13% of sarcomas displayed high topo I, high proliferation, and normal p53.
Conclusions:
- High topo I levels, active DNA replication, and normal p53 expression are potential predictive biomarkers for topo I-targeted therapy in human sarcomas.
- These molecular parameters may guide treatment selection for sarcoma patients.
- Further studies are warranted to confirm the clinical utility of these markers.