== Time course of boron accumulation. 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] -rays (P< 0.01). Nuclear condensation was determined using both a fluorescence technique and electron microscopy in all cell lines treated with MSX-130 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] -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 -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 malignancies. Despite aggressive surgery combined with adjuvant radiotherapy and chemotherapy, patient prognosis remains poor. It is thus essential to develop novel 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 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 diameter of a single cell; the lethality of these nuclei is thus primarily limited to boron-containing cells [3]. BNCT has been carried out in numerous studies using syngeneic rat gliomas [3-6]. Approaches such as administering [10B] by intra-arterial injection with or without blood-brain barrier (BBB) disruption [7-9], or intracerebral delivery of high molecular weight agents by means of convection enhanced delivery following neutron beam irradiation [2,10], confirm that BNCT is highly effective for treatment glioma xenograft models. In clinic, BNCT has been used in various countries MSX-130 to treat patients with high-grade glioma, melanoma, liver metastasis of colon adenocarcioma, malignant melanomas, MSX-130 oral cancer, and therapeutically refractory, recurrent tumors of the head and neck [3,6,11-15]; while the mechanism of BNCT-induced cell death remains unclear. We treated U87, U251, and SHG44 glioma MSX-130 cells with Rabbit Polyclonal to JAK2 (phospho-Tyr570) BNCTin vitro, using L-p-borono-phenylalanine (L-BPA) as the boron carrier and the thermal neutron source of the Xi’an Pulsed Reactor (XAPR) in China as the irradiator. The relative biological effect (RBE) of BNCT on tested cells, especially with respect to apoptosis induction, was assessed, and MSX-130 a possible mechanism of BNCT action was presented. == Methods == == Glioma cell culture == The human glioblastoma multiforme cell lines U87 and U251 were obtained from the American Type Culture Collection (ATCC; Manassas, VA). The human anaplastic astrocytoma cell line SHG44 was purchased from the Institute of Biochemistry and Cell Biology (IBCB; Shanghai, China). Cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Gibco, Grand Island, NY) with 10% (v/v) fetal bovine serum (Gibco) and 0.5% (w/v) penicillin-streptomycin solution (Gibco), at 37C under 5% CO2and 95% air (both v/v). == Boron uptake by glioma cellsin vitro == [10B]-enriched L-BPA (Ryscor Inc., Raleigh, NC) was used in the study. L-BPA was added to the culture media of glioma cells to 50 g [10B]/ml. Cells in the exponential phase of growth were cultured in boron-containing medium for 3, 6, 12, or 24 h before harvesting, and boron concentrations were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) (VISTA-MPX; Varian Co., Walnut Creek, CA).