Wang et al. BMC Cancer 2010, 10:661 http://www.biomedcentral.com/1471-2407/10/661 R E S E A R C H A R T I C L E Open Access Boron neutron capture therapy induces apoptosis of glioma cells through Bcl-2/Bax Peng Wang1†, Haining Zhen1†, Xinbiao Jiang2†, Wei Zhang1, Xin Cheng3, Geng Guo1, Xinggang Mao1, Xiang Zhang1* Abstract Background: Boron neutron capture therapy (BNCT) is an alternative treatment modality for patients with glioma. The aim of this study was to determine whether induction of apoptosis contributes to the main therapeutic efficacy of BNCT and to compare the relative biological effect (RBE) of BNCT, g-ray and reactor neutron irradiation. Methods: The neutron beam was obtained from the Xi’an Pulsed Reactor (XAPR) and g-rays were obtained from [60Co] g source of the Fourth Military Medical University (FMMU) in China. Human glioma cells (the U87, U251, and SHG44 cell lines) were irradiated by neutron beams at the XAPR or [60Co] g-rays at the FMMU with different protocols: Group A included control nonirradiated cells; Group B included cells treated with 4 Gy of [60Co] g-rays; Group C included cells treated with 8 Gy of [60Co] g-rays; Group D included cells treated with 4 Gy BPA (p-borono- phenylalanine)-BNCT; Group E included cells treated with 8 Gy BPA-BNCT; Group F included cells irradiated in the reactor for the same treatment period as used for Group D; Group G included cells irradiated in the reactor for the same treatment period as used for Group E; Group H included cells irradiated with 4 Gy in the reactor; and Group I included cells irradiated with 8 Gy in the reactor. Cell survival was determined using the 3-(4,5-dimethylthiazol-2-yl- 2,5-diphenyltetrazolium (MTT) cytotoxicity assay. The morphology of cells was detected by Hoechst33342 staining and transmission electron microscope (TEM). The apoptosis rate was detected by flow cytometer (FCM). The level of Bcl-2 and Bax protein was measured by western blot analysis. Results: Proliferation of U87, U251, and SHG44 cells was much more strongly inhibited by BPA-BNCT than by irradiation with [60Co] g-rays (P < 0.01). Nuclear condensation was determined using both a fluorescence technique and electron microscopy in all cell lines treated with BPA-BNCT. Furthermore, the cellular apoptotic rates in Group D and Group E treated with BPA-BNCT were significantly higher than those in Group B and Group C irradiated by [60Co] g-rays (P < 0.01). The clonogenicity of glioma cells was reduced by BPA-BNCT compared with cells treated in the reactor (Group F, G, H, I), and with the control cells (P < 0.01). Upon BPA-BNCT treatment, the Bax level increased in glioma cells, whereas Bcl-2 expression decreased. Conclusions: Compared with g-ray and reactor neutron irradiation, a higher RBE can be achieved upon treatment of glioma cells with BNCT. Glioma cell apoptosis induced by BNCT may be related to activation of Bax and downregulation of Bcl-2. Background Glioma is one of the most aggressive human malignan- cies. Despite aggressive surgery combined with adjuvant radiotherapy and chemotherapy, patient prognosis remains poor. It is thus essential to develop novel * Correspondence: xzhang@fmmu.edu.cn † Contributed equally 1Department of Neurosurgery of Xijing Hospital, Fourth Military Medical University, Xi’an, Shaanxi 710032, P.R.China Full list of author information is available at the end of the article therapeutic strategies to treat glioma. Boron neutron capture therapy (BNCT) is a highly selective treatment modality that can target the tumor without causing excessive radiation damage to the normal tissues [1]. The ability of [10B] to capture thermal neutrons, and to then disintegrate immediately into a He nucleus (an a particle) and a Li nucleus, is utilized in BNCT [2]. Both the He and Li nuclei have high lineal energy transfer (LET) values, with path-lengths approximately the dia- meter of a single cell; the lethality of these nuclei is thus © 2010 Wang et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.