Inhibition of the glucocorticoid receptor results in an enhanced miR-99a/100-mediated radiation response in stem-like cells from human prostate cancers
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Jayant K. Rane1,5,*, Holger H.H. Erb1,*, Giovanna Nappo1,6, Vincent M. Mann2,3, Matthew S. Simms2,3, Anne T. Collins1, Tapio Visakorpi4, Norman J. Maitland1,2
1The Cancer Research Unit, Department of Biology, University of York, York, North Yorkshire, YO10 5DD, UK
2Hull York Medical School, University of Hull, Hull, East Yorkshire, HU6 7RX, UK
3Department of Urology, Castle Hill Hospital, Cottingham, East Yorkshire, HU16 5JQ, UK
4Prostate Cancer Research Center, Institute of Biosciences and Medical Technology - BioMediTech, University of Tampere and Tampere University Hospital, Tampere, 33520 Finland
5Leukaemia and Stem Cell Biology Group, Department of Haematological Medicine, King’s College London, Rayne Institute, London, SE5 9NU, UK
6Laboratory of Molecular Haematopoiesis and Stem Cell Biology, Department of Experimental and Clinical Medicine, Magna Græcia University, 88100, Catanzaro, Italy
*These authors have contributed equally to this work
Holger H.H. Erb, email: [email protected]
Keywords: cancer stem cells, miRNA, radiotherapy, DNA damage repair, mifepristone
Received: May 03, 2016 Accepted: June 09, 2016 Published: June 21, 2016
Radiation therapy is a major primary treatment option for both localized early stage prostate cancer, and for advanced, regionally un-resectable, cancer. However, around 30% of patients still experience biochemical recurrence after radiation therapy within 10 years. Thus, identification of better biomarkers and new targets are urgently required to improve current therapeutic strategies. The miR-99 family has been shown to play an important role in the regulation of the DNA damage response, via targeting of the SWI/SNF chromatin remodeling factors, SMARCA5 and SMARCD1 in cell line models. In the present study, we have demonstrated that low expression of miR-99a and miR-100 is present in cell populations which are relatively radiation insensitive, for example in prostate cancer stem cells and in castration-resistant prostate cancer. Additionally, treatment of cells with the synthetic glucocorticoid, Dexamethasone resulted in decreased miR-99a and 100 expression, suggesting a new mechanism of miR-99a and 100 regulation in androgen-independent prostate cells. Strikingly, treatment of prostate cells with the glucocorticoid receptor inhibitor, Mifepristone was found to sensitize prostate cells to radiation by increasing the levels of miR-99a and miR-100. These results qualify the miR99 family as markers of radiation sensitivity and as potential therapeutic targets to improve efficiency of radiotherapy.
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