• Bong, Jin-Jong (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd) ;
  • Kang, Yu-Mi (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd) ;
  • Shin, Suk-Chul (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd) ;
  • Choi, Moo-Hyun (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd) ;
  • Choi, Seung-Jin (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd) ;
  • Lee, Kyung-Mi (Global Research Lab, BAERI Institute, Department of Biochemistry and Molecular Biology, Korea University College of Medicine) ;
  • Kim, Hee-Sun (Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd)
  • Received : 2012.03.08
  • Accepted : 2012.04.14
  • Published : 2012.06.30


To determine the biological effects of low-dose-rate radiation ($^{137}Cs$, 2.95 mGy/h) on EL4 lymphoma cells during 24 h, we investigated the expression of genes related to apoptosis, cell cycle arrest, DNA repair, iron transport, and ribonucleotide reductase. EL4 cells were continuously exposed to low-dose-rate radiation (total dose: 70.8 mGy) for 24 h. We analyzed cell proliferation and apoptosis by trypan blue exclusion and flow cytometry, gene expression by real-time PCR, and protein levels with the apoptosis ELISA kit. Apoptosis increased in the Low-dose-rate irradiated cells, but cell number did not differ between non- (Non-IR) and Low-dose-rate irradiated (LDR-IR) cells. In concordance with apoptotic rate, the transcriptional activity of ATM, p53, p21, and Parp was upregulated in the LDR-IR cells. Similarly, Phospho-p53 (Ser15), cleaved caspase 3 (Asp175), and cleaved Parp (Asp214) expression was upregulated in the LDR-IR cells. No difference was observed in the mRNA expression of DNA repair-related genes (Msh2, Msh3, Wrn, Lig4, Neil3, ERCC8, and ERCC6) between Non-IR and LDR-IR cells. Interestingly, the mRNA of Trfc was upregulated in the LDR-IR cells. Therefore, we suggest that short-term Low-dose-rate radiation activates apoptosis in EL4 lymphoma cells.


  1. Fleenor CJ, Marusyk A, DeGregori J. Ionizing radiation and hematopoietic malignancies: altering the adaptive landscape. Cell Cycle. 2010;9:3005-3011.
  2. Mitchel RE, Burchart P, Wyatt H. A lower dose threshold for the in vivo protective adaptive response to radiation. Tumorigenesis in chronically exposed normal and Trp53 heterozygous C57BL/6 mice. Radiat. Res. 2008;170:765-775.
  3. Kirsch DG, Santiago PM, di Tomaso E, Sullivan JM, Hou WS, Dayton T, Jeffords LB, Sodha P, Mercer KL, Cohen R, Takeuchi O, Korsmeyer SJ, Bronson RT, Kim CF, Haigis KM, Jain RK, Jacks T. p53 controls radiation-induced gastrointestinal syndrome in mice independent of apoptosis. Science. 2010;327: 593-596.
  4. Zhao BX, Chen HZ, Du XD, Luo J, He JP, Wang RH, Wang Y, Wu R, Hou RR, Hong M, Wu Q. Orphan receptor TR3 enhances p53 transactivation and represses DNA double-strand break repair in hepatoma cells under ionizing radiation. Mol. Endocrinol. 2011;25:1337-1350.
  5. Meador JA, Ghandhi SA, Amundson SA. p53-Independent downregulation of histone gene expression in human cell lines by high- and low-LET radiation. Radiat. Res. 2011;175:689-699.
  6. Squatrito M, Brennan CW, Helmy K, Huse JT, Petrini JH, Holland EC. Loss of ATM/Chk2/p53 pathway components accelerates tumor development and contributes to radiation resistance in gliomas. Cancer Cell. 2010;18:619-629.
  7. UNCLEAR, United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionizing Radiation, Vols. I and II. United Nations, New York. 2000.
  8. Portess DI, Bauer G, Hill MA, O'Neill P. Low-dose irradiation of nontransformed cells stimulates the selective removal of precancerous cells via intercellular induction of apoptosis. Cancer Res. 2007; 67:1246-1253.
  9. Levine AJ. p53, the cellular gatekeeper for growth and division. Cell. 1997;88:323-331.
  10. Shieh SY, Ikeda M, Taya Y, Prives C. DNA damage -induced phosphorylation of p53 alleviates inhibition by Mdm2. Cell. 1997;91:325-334.
  11. Chehab NH, Malikzay A, Stavridi ES, Halazonetis TD. Phosphorylation of Ser-20 mediates stabilization of human p53 in response to DNA damage. Proceedings of the National Academy of Sciences of the United States of America. 1999;96:13777-13782.
  12. Honda R, Tanaka H, Yasuda H. Oncoprotein Mdm2 is a ubiquitin ligase E3 for tumor suppressor p53. FEBS Lett. 1997;420:25-27.
  13. Tibbetts RS, Brumbaugh KM, Williams JM, Sarkaria JN, Cliby WA, Shieh SY, Taya Y, Prives C, Abraham RT. A role for ATR in the DNA damage-induced phosphorylation of p53. Genes & Development. 1999;13:152-157.
  14. Mendrysa SM, McElwee MK, Michalowski J, O'Leary KA, Young KM, Perry ME. mdm2 Is critical for inhibition of p53 during lymphopoiesis and the response to ionizing irradiation. Mol. Cell. Biol. 2003;23:462-472.
  15. Sugihara T, Murano H, Nakamura M, Ichinohe K, Tanaka K. p53-Mediated gene activation in mice at high doses of chronic low-dose-rate ${\gamma}$ radiation. Radiat. Res. 2011;175:328-335.
  16. Sugihara T, Magae J, Wadhwa R, Kaul SC, Kawakami Y, Matsumoto T, Tanaka K. Dose and dose-rate effects of low-dose ionizing radiation on activation of Trp53 in immortalized murine cells. Radiat. Res. 2004;162:296-307.
  17. Slee EA, Benassi B, Goldin R, Zhong S, Ratnayaka I, Blandino G, Lu X. Phosphorylation of Ser312 contributes to tumor suppression by p53 in vivo. Proceedings of the National Academy of Sciences of the United States of America. 2010;107:19479-19484.
  18. Limesand KH, Schwertfeger KL, Anderson SM. Mdm2 is required for suppression of apoptosis by activated Akt1 in salivary acinar cells. Mol. Cell Biol. 2006;26:8840-8856.
  19. Mitchell GC, Fillinger JL, Sittadjody S, Avila JL, Burd R, Limesand KH. Igf1 activates cell cycle arrest following irradiation by reducing binding of ${\Delta}$ Np63 to the p21 promoter. Cell Death. Dis. 2010; 2010:e50
  20. Tsai CY, Ray AS, Tumas DB, Keating MJ, Reiser H, Plunkett W. Targeting DNA repair in chronic lymphocytic leukemia cells with a novel acyclic nucleotide analogue, GS-9219. Clin. Cancer Res. 2009;15:3760-3769.
  21. Fernandes-Alnemri T, Litwack G, Alnemri ES. CPP32, a novel human apoptotic protein with homology to Caenorhabditis elegans cell death protein Ced-3 and mammalian interleukin-1 beta-converting enzyme. J. Biol. Chem. 1994; 269:30761-30764.
  22. Nicholson DW, Ali A, Thornberry NA, Vaillancourt JP, Ding CK, Gallant M, Gareau Y, Griffin PR, Labelle M, Lazebnik YA, et al. Identification and inhibition of the ICE/CED-3 protease necessary for mammalian apoptosis. Nature. 1995;376:37-43.
  23. Yu HS, Xue HW, Guo CB, Song AQ, Shen FZ, Liang J, Deng C. Low dose radiation increased the therapeutic efficacy of cyclophosphamide on S(180) sarcoma bearing mice. J. Radiat. Res. 2007;48:281-288.
  24. Kannan S, Fang W, Song G, Mullighan CG, Hammitt R, McMurray J, Zweidler-McKay PA. Notch/HES1-mediated Parp1 activation: a cell type-specific mechanism for tumor suppression. Blood. 2011;117:2891-2900.
  25. Abela RA, Qian J, Xu L, Lawrence TS, Zhang M. Radiation improves gene delivery by a novel transferrin-lipoplex nanoparticle selectively in cancer cells. Cancer Gene. Ther. 2008;15:496-507.
  26. Chen Z, Nomura J, Suzuki T, Suzuki N. Enhanced expression of transferrin receptor confers UV-resistance in human and monkey cells. J. Radiat. Res. 2005;46:443-451.
  27. Kunos CA, Radivoyevitch T, Pink J, Chiu SM, Stefan T, Jacobberger J, Kinsella TJ. Ribonucleotide reductase inhibition enhances chemoradiosensitivity of human cervical cancers. Radiat. Res. 2010;174: 574-581.