Silencing CDK4 radiosensitizes breast cancer cells by promoting apoptosis

Cell Division

Harold I Saavedra¹  Xingming Deng¹  Ruth M O’Regan³  Yuan Liu²  Sandra S Zaky¹  Mary Kathryn Harrison Pitner¹  Shannon Tucker Kahn¹  Mi-Young Lee¹  Xiangbin Zeng¹  Katie R Hagen¹ 

[1] Department of Radiation Oncology, Emory University School of Medicine, Atlanta, USA;Department of Biostatistics and Bioinformatics, Emory University School of Public Health, Atlanta, USA;Department of Medical Oncology, Emory University School of Medicine, Atlanta, USA

关键词: Apoptosis;    Breast cancer;    Radiosensitization;    Radioresistance;    Bad;    Radiation;    CDK2;    CDK4;   

Others  :  790514
DOI  :  10.1186/1747-1028-8-10

 received in 2013-04-03, accepted in 2013-07-18,  发布年份 2013

【 摘 要 】

Background

The discovery of molecular markers associated with various breast cancer subtypes has greatly improved the treatment and outcome of breast cancer patients. Unfortunately, breast cancer cells acquire resistance to various therapies. Mounting evidence suggests that resistance is rooted in the deregulation of the G1 phase regulatory machinery.

Methods

To address whether deregulation of the G1 phase regulatory machinery contributes to radiotherapy resistance, the MCF10A immortalized human mammary epithelial cell line, ER-PR-Her2+ and ER-PR-Her2- breast cancer cell lines were irradiated. Colony formation assays measured radioresistance, while immunocytochemistry, Western blots, and flow cytometry measured the cell cycle, DNA replication, mitosis, apoptosis, and DNA breaks.

Results

Molecular markers common to all cell lines were overexpressed, including cyclin A1 and cyclin D1, which impinge on CDK2 and CDK4 activities, respectively. We addressed their potential role in radioresistance by generating cell lines stably expressing small hairpin RNAs (shRNA) against CDK2 and CDK4. None of the cell lines knocked down for CDK2 displayed radiosensitization. In contrast, all cell lines knocked down for CDK4 were significantly radiosensitized, and a CDK4/CDK6 inhibitor sensitized MDA-MB-468 to radiation induced apoptosis. Our data showed that silencing CDK4 significantly increases radiation induced cell apoptosis in cell lines without significantly altering cell cycle progression, or DNA repair after irradiation. Our results indicate lower levels of phospho-Bad at ser136 upon CDK4 silencing and ionizing radiation, which has been shown to signal apoptosis.

Conclusion

Based on our data we conclude that knockdown of CDK4 activity sensitizes breast cancer cells to radiation by activating apoptosis pathways.

【 授权许可】

   
2013 Hagen et al.; licensee BioMed Central Ltd.

【 图 表 】

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