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miR-206 expression is downregulated in cyclin D1 amplified breast tumours
Linköping University, Department of Clinical and Experimental Medicine, Oncology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Oncology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Oncology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Oncology UHL.
Department of Cytology, Karolinska University Hospital, SE-104 01 Stockholm, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Amplification in the 11q13 region has been found in around 15% of all breast cancers and is strongly correlated with oestrogen receptor (ER) positive tumours. We have previously found that amplification of at least one of the genes PAK1 or CCND1 is associated with decreased recurrencefree survival among ER+ patients. Other genes in the amplicon might also contribute to this effect and situated close to CCND1 are the FGF-3, -4 and - 19 genes. The FGF-4 protein has been shown to inhibit the expression of the ERα regulator miR-206 in chicken embryo. In this study we analysed 23 tumours with and 27 tumours without previously detected 11q13 amplification to explore if 11q13 amplification is associated with decreased levels of miR-206 and if miR-206 is associated with ER expression. Using real-time PCR, we found that miR-206 expression was inversely correlated to CCND1 and 11q13 amplification (P=0.016 and P=0.022 respectively). Tumours with low miR-206 expression had higher levels of ERα than tumours with intermediate and high expression (P=0.043). We conclude that miR-206 might be an important regulator of the ERα. Our finding that low mir-206 is associated with CCND1 amplification and thereby also FGF-4 amplification points towards the possibility of a miR-206 regulator, FGF-4 or another FGF, present in the amplicon.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-17457OAI: oai:DiVA.org:liu-17457DiVA: diva2:209566
Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2010-01-14Bibliographically approved
In thesis
1. Cell cycle alterations and 11q13 amplification in breast cancer: prediction of adjuvant treatment response
Open this publication in new window or tab >>Cell cycle alterations and 11q13 amplification in breast cancer: prediction of adjuvant treatment response
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The growth and development of the breast is to a large extent regulated by oestrogens through the oestrogen receptor (ER). Activation of the ERα triggers transcription of genes that are important for cell proliferation and stimulates entry into the G1 phase of the cell cycle. In breast cancer the ERα is often upregulated and is therefore a suitable target for adjuvant therapies such as tamoxifen. Although tamoxifen is an effective treatment in most cases, tumours sometimes acquire resistance to the drug. The aim of this thesis was to investigate the impact of G1 phase proteins and 11q13 amplification on prognosis and treatment response in breast cancer. The material used was from a clinical trial in which postmenopausal breast cancer patients were randomised to chemotherapy or radiotherapy and tamoxifen or no adjuvant treatment. We studied the expression of cyclin D1, cyclin E and Rb with immunohisochemistry and amplification of CCND1 and PAK1 with real time PCR. We found that among patients with high tumour expression of cyclin D1, overexpression of ErbB2 was associated with reduced recurrence-free survival. Both cyclin D1 and cyclin E overexpression were associated with reduced tamoxifen response. High expression of cyclin D1 has been found to induce ligand independent activation of ERα in breast cancer cells and might also switch tamoxifen from acting as an antagonist to an agonist. Overexpression of cyclin E has been shown to be associated with expression of low molecular weight isoforms of the protein that possess an increased kinase activity and are insensitive to p21 and p27 inhibition. Furthermore, amplification of 11q13, and in particular the gene PAK1, was a strong predictor of tamoxifen resistance. The pak1 protein is involved in phosphorylation and ligand independent activation of the ERα. We also found that lost expression of either p53 or Rb reduced the patients benefit from radiotherapy compared with patients with normal expression of both proteins. Normally, ionizing radiation upregulates p53 resulting in G1 arrest or apoptosis. If either functional p53 or Rb is missing the cells can proceed from G1 to the S phase despite damaged DNA. The expression of the microRNA, miR-206, was analysed with real time PCR, and the results showed that high expression of miR-206 correlated to low expression of ERα and 11q13 amplification. In vitro studies have shown that miR-206 negatively regulates the expression of ERα. Taken together the G1 regulators and amplification of 11q13 seem to have an important role in predicting the patient’s response to adjuvant therapy.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 68 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1102
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-17458 (URN)978-91-7393-690-3 (ISBN)
Public defence
2009-04-17, Linden, Hälsouniversitetet, Campus HU, Linköpings universitet, Linköping, 09:00 (Swedish)
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Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2009-08-21Bibliographically approved

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Ahnström Waltersson, MarieKarlsson, ElinNordenskjöld, BoStål, Olle

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