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Volume 2014 (2014), Article ID 438030, 10 pages
Research Article

Radiosensitivity and Induction of Apoptosis by High LET Carbon Ion Beam and Low LET Gamma Radiation: A Comparative Study

1Department of Biochemistry & Biophysics, University of Kalyani, Kalyani 741235, India
2Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India
3Inter-University Accelerator Center (IUAC), Aruna Asaf Ali Marg, New Delhi 110067, India

Received 20 February 2014; Accepted 22 May 2014; Published 15 June 2014

Academic Editor: Nicolaas A. Franken

Copyright © 2014 Atanu Ghorai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cancer treatment with high LET heavy ion beam, especially, carbon ion beam (12C), is becoming very popular over conventional radiotherapy like low LET gamma or X-ray. Combination of Poly(ADP-ribose) polymerase (PARP) inhibitor with xenotoxic drugs or conventional radiation (gamma or X-ray) is the newer approach for cancer therapy. The aim of our study was to compare the radiosensitivity and induction of apoptosis by high LET 12C and low LET gamma radiation in HeLa and PARP-1 knocked down cells. We did comet assay to detect DNA breaks, clonogenic survival assay, and cell cycle analysis to measure recovery after DNA damage. We measured apoptotic parameters like nuclear fragmentation and caspase-3 activation. DNA damage, cell killing, and induction of apoptosis were significantly higher for 12C than gamma radiation in HeLa. Cell killing and apoptosis were further elevated upon knocking down of PARP-1. Both 12C and gamma induced G2/M arrest although the 12C had greater effect. Unlike the gamma, 12C irradiation affects DNA replication as detected by S-phase delay in cell cycle analysis. So, we conclude that high LET 12C has greater potential over low LET gamma radiation in killing cells and radiosensitization upon PARP-1 inhibition was several folds greater for 12C than gamma.