miR-210 as a marker of chronic hypoxia, but not a therapeutic target in prostate cancer

Introduction: Radiotherapy in combination with medical castration is the standard treatment for high-risk prostate cancer. Some relapses may be explained by the presence of radioresistant clones arising from hypoxic microenvironment. Since microRNAs (miR) are increased upon hypoxia, the aim of this study was to see whether miR-210 is a potential marker for hypoxia and/or a therapeutic target in prostate cancer. Methods: Human LNCaP, DU145 or PC:3 prostate cancer cells were exposed to normoxia or hypoxia for several hours. Gene expression of miR-210, miR-373 and several hypoxia markers were analyzed by Taqman and SYBR green qRT-PCR, respectively. Clonogenic survival after LNA miR-210 inhibitor (78 nM) and concomitant irradiation were evaluated. Results: During anoxia, CAIX and VEGF expressions were dramatically increased. miR-210 expression increased during anoxia exposure, while basal miR-373 expression was low and remained stable upon anoxia. LNA miR-210 inhibitor decreased anoxic miR-210 expression by 90% and clonogenic survival under anoxia (p = 0.01). However, no enhanced effect was observed when miR-210 inhibitor was combined with irradiation. Conclusion: miR-210 could be an interesting marker of chronic hypoxia irrespective of the androgen dependency and should, therefore, be tested as a prognostic marker in high risk prostate cancer patients. (C) 2011 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 101 (2011) 203-208