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Kümler I, Balslev E, Poulsen TS, Nielsen SL, Nygård SB, Rømer MU, Christensen IJ, Høgdall E, Moreira J, Nielsen DL, Brünner N, Stenvang J. Topoisomerase-1 gene copy aberrations are frequent in patients with breast cancer. Int J Cancer 2015; 137:2000-6. [PMID: 25855483 DOI: 10.1002/ijc.29556] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 03/05/2015] [Accepted: 03/24/2015] [Indexed: 11/07/2022]
Abstract
Topoisomerase-1 (Top1) targeting drugs have shown promising efficacy in patients with metastatic breast cancer (BC). However, these drugs are rather toxic calling for development and validation of predictive biomarkers to increase the therapeutic index. As these drugs are targeting the Top1 protein and since no validated anti-Top1 antibodies for immunohistochemistry have been reported, we raised the hypothesis that TOP1 gene amplifications may serve as a proxy for the Top1 protein and thereby a biomarker of response to treatment with Top1 inhibitors in BC. The aim was to determine the prevalence of TOP1 gene copy gain in BC. The prevalence of TOP1 gene copy gain was investigated by fluorescence in situ hybridization with a TOP1/CEN-20 probemix in normal breast tissue (N = 100) and in tissue from patients with metastatic BC in a discovery (N = 100) and a validation cohort (N = 205). As amplification of 20q including CEN-20 is common in BC a TOP1/CEN-2 probemix was applied to the validation cohort. More than 30% of the patients had gene copy numbers of ≥ 4 and ∼20% of the patients had TOP1/CEN-20 ratios ≥ 1.5. The CEN-2 probe did not add any information. Gain of the TOP1 gene appears to be common in BC making the gene a potential biomarker for response to treatment with Top1 inhibitors. As 20q amplification is a common finding in BC and as no other suitable reference gene has yet been identified, TOP1 copy number may be a more valid method of detecting gain than using a gene/centromere ratio.
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Affiliation(s)
- Iben Kümler
- Department of Oncology, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - Eva Balslev
- Department of Pathology, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - Tim S Poulsen
- Department of Pathology, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - Signe Lykke Nielsen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Sune Boris Nygård
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Maria Unni Rømer
- Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, University of Copenhagen, Glostrup, Denmark
| | - Ib Jarle Christensen
- The Finsen Laboratory, Rigshospitalet and Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Denmark
| | - Estrid Høgdall
- Department of Pathology, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - José Moreira
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Dorte L Nielsen
- Department of Oncology, Herlev Hospital, University of Copenhagen, Herlev, Denmark
| | - Nils Brünner
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Jan Stenvang
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
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