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C Elizabeth Caldon,
C Marcelo Sergio,
Jian Kang,
Anita Muthukaruppan,
Marijke N Boersma, Andrew Stone,
Jane Barraclough,
Christine S Lee,
Michael A Black,
Lance D Miller,
Julia M Gee,
Rob I Nicholson,
Robert L Sutherland,
Cristin G Print,
Elizabeth A Musgrove
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ABSTRACT: Cyclin E2, but not cyclin E1, is included in several gene signatures that predict disease progression in either tamoxifen-resistant or metastatic breast cancer. We therefore examined the role of cyclin E2 in antiestrogen resistance in vitro and its potential for therapeutic targeting through cyclin-dependent kinase (CDK) inhibition. High expression of CCNE2, but not CCNE1, was characteristic of the luminal B and HER2 subtypes of breast cancer and was strongly predictive of shorter distant metastasis-free survival following endocrine therapy. After antiestrogen treatment of MCF-7 breast cancer cells, cyclin E2 mRNA and protein were downregulated and cyclin E2-CDK2 activity decreased. However, this regulation was lost in tamoxifen-resistant (MCF-7 TAMR) cells, which overexpressed cyclin E2. Expression of either cyclin E1 or E2 in T-47D breast cancer cells conferred acute antiestrogen resistance, suggesting that cyclin E overexpression contributes to the antiestrogen resistance of tamoxifen-resistant cells. Ectopic expression of cyclin E1 or E2 also reduced sensitivity to CDK4, but not CDK2, inhibition. Proliferation of tamoxifen-resistant cells was inhibited by RNAi-mediated knockdown of cyclin E1, cyclin E2, or CDK2. Furthermore, CDK2 inhibition of E-cyclin overexpressing cells and tamoxifen-resistant cells restored sensitivity to tamoxifen or CDK4 inhibition. Cyclin E2 overexpression is therefore a potential mechanism of resistance to both endocrine therapy and CDK4 inhibition. CDK2 inhibitors hold promise as a component of combination therapies in endocrine-resistant disease as they effectively inhibit cyclin E1 and E2 overexpressing cells and enhance the efficacy of other therapeutics.
Molecular Cancer Therapeutics 05/2012; 11(7):1488-99. · 5.23 Impact Factor
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ABSTRACT: The cell cycle is a tightly regulated series of events that governs cell replication and division. Deregulation of cell cycle kinases, e.g., cyclin-dependent kinases (CDKs), can initiate a hyper-proliferative cell phenotype and cause genomic instability, thus facilitating malignant transformation. Pharmacological agents targeting CDKs have been developed as potential anti-cancer agents for over 20 years, evolving from early pan-CDK inhibitors to second-generation inhibitors with much greater specificity and selectivity. Despite these advances in drug design and highly successful preclinical investigations, CDK inhibitors have yet to achieve their expected efficacy in clinical trials. In addition, inhibitors of other cell cycle kinases are currently progressing through clinical trials. Recent biochemical and genetic studies might be used to improve the effectiveness of cell cycle kinase inhibitors as anti-cancer agents through better drug design, therapeutic combinations, and patient selection.
Critical reviews in oncogenesis 01/2012; 17(2):175-98.
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ABSTRACT: Cyclin D1, and to a lesser extent the other D-type cyclins, is frequently deregulated in cancer and is a biomarker of cancer phenotype and disease progression. The ability of these cyclins to activate the cyclin-dependent kinases (CDKs) CDK4 and CDK6 is the most extensively documented mechanism for their oncogenic actions and provides an attractive therapeutic target. Is this an effective means of targeting the cyclin D oncogenes, and how might the patient subgroups that are most likely to benefit be identified?
Nature Reviews Cancer 01/2011; 11(8):558-72. · 29.54 Impact Factor
