UHRF1 confers radioresistance to human breast cancer cells.
OBJECTIVE
To investigate the effect of ubiquitin-like with plant homeodomain (PHD) and ring finger domains 1 (UHRF1) overexpression on radiosensitivity to X-rays in human breast cancer MDA-MB-231 cells.


METHODS
Cell survival was determined by colony formation assay; cell cycle distribution was measured by flow cytometry; apoptosis was evaluated by DNA fragmentation assay and Annexin V apoptosis detection kit; protein expression was analysed by Western blot assay; chromosome aberrations (centric rings and dicentrics) were assayed by conventional chromosome analysis.


RESULTS
A significant decrease of radiosensitivity to X-rays was observed in MDA-MB-231 cells transfected with a full-length of human UHRF1 cDNA (MDA-MB-231/UHRF1) compared to the control cells (MDA-MB-231/parental and MDA-MB-231/pcDNA3 [mammalian expression vector]), and the similar results were observed in MDA-MB-468 cells. In contrast, a decreased expression of UHRF1 by a specific UHRF1-small interfering RNA (siRNA) significantly enhanced cell radiosensitivity. The UHRF1-mediated radioresistance was correlated with a G2(Ra)/M arrest, a decreased induction of apoptosis, a down-regulation of the pro-apoptotic protein anti-B cell lymphoma/leukemia 2 (bcl-2) associated X protein (Bax) and a up-regulation of the DNA damage repair proteins Lupus Ku autoantigen protein p70 (Ku-70) and Lupus Ku autoantigen protein p80 (Ku-80). Furthermore, chromosomal aberrations (centric rings and dicentrics) by X-rays were less in MDA-MB-231/UHRF1 than in MDA-MB-231/parental and MDA-MB-231/pcDNA3 control cells.


CONCLUSIONS
These results suggested that UHRF1 may be a new target in the radiotherapy of breast cancer via affecting apoptosis and DNA damage repair.
School of Radiation Medicine and Public Health, Medical College of Soochow University, Suzhou, Jiangsu, P. R. China.
Xinli
X
Li
Qinghui
Q
Meng
Eliot M
EM
Rosen
Saijun
S
Fan
D000818:Animals; D017304:Annexin A5 / Q000494:pharmacology; D034961:Antigens, Nuclear / Q000494:pharmacology; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D000072200:Ku Autoantigen; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D011836:Radiation Tolerance; D044767:Ubiquitin-Protein Ligases; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D017304:Annexin A5; D034961:Antigens, Nuclear; C494826:BAX protein, human; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051028:bcl-2-Associated X Protein; C406364:UHRF1 protein, human; D044767:Ubiquitin-Protein Ligases; C117054:Uhrf1 protein, mouse; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen