ABSTRACT
To establish metabolic context for radiation sensitivity by measuring autophagic flux in two different glioblastoma (GBM) cell lines. Clonogenic survival curve analysis of U87 or U251 cells exposed to γ radiation, fast neutrons, a mixed energy neutron beam (METNB) or Auger electrons from a gadolinium neutron capture (GdNC) reaction suggested other factors, beyond a defective DNA damage response, contribute to cell death of U251 cells. Altered tumor metabolism (autophagy) was hypothesized as a factor in U251 cells' clonogenic response. Each of the four different radiation modalities induced an increase in the number of autophagosomes in both U87 and U251 cells. Changes in the number of autophagosomes can be explained by either induction of autophagy or alterations in autophagic flux so autophagic flux was assayed by p62 immunoblotting or in engineered GBM cells that stably express an autophagy marker protein, LC3B-eGFP-mCherry. Perturbations in later stages of autophagy in U251 cells corresponded with radiation sensitivity of U251 cells irradiated with 10 Gy γ rays. Establishment of altered autophagic flux is a useful biomarker for metabolic stress and provided metabolic context for radiation sensitization to 10 Gy γ rays. These results provide strong evidence for the usefulness of managing tumor cell metabolism as a tool for the enhancement of radiation therapy.
Subject(s)
Autophagosomes/radiation effects , Autophagy/radiation effects , DNA Damage , Electrons/therapeutic use , Glioblastoma/genetics , Glioblastoma/radiotherapy , Autophagosomes/pathology , Cell Line, Tumor , Dose-Response Relationship, Radiation , Gamma Rays/therapeutic use , Glioblastoma/pathology , Humans , Neutrons/therapeutic use , Radiotherapy DosageABSTRACT
A modified enhanced thermal neutron beam (METNB) assembly at Fermilab was used to irradiate borylphenylalanine (BPA) treated human prostate cancer cells, DU 145. Acceptable cellular uptake levels of BPA and no BPA cytotoxicity were observed. In the absence of BPA, the relative biological effectiveness (RBE) of the METNB was determined to be 2.3-4.8 times greater than gamma rays. An additional 1.2 or 1.4 fold relative enhancement from boron neutron capture (RE(BNC)) was observed for METNB irradiated DU 145 cells treated with 4.9 or 12mM BPA, respectively. The additional cell killing of the BPA loaded DU 145 cells by the METNB at Fermilab is evidence for a BNC enhanced cell killing.
Subject(s)
Boron Neutron Capture Therapy/methods , Prostatic Neoplasms/pathology , Prostatic Neoplasms/radiotherapy , Cell Line, Tumor , Dose-Response Relationship, Radiation , Humans , Male , Radiotherapy Dosage , Treatment OutcomeABSTRACT
PURPOSE: A proof of principle for cell killing by Gadolinium (Gd) neutron capture in Magnevist preloaded Glioblastoma multiforme (GBM) cells is provided. MATERIALS AND METHODS: U87cells were pre-loaded with 5 mg/ml Magnevist (Gd containing compound) and irradiated using an enhanced neutron beam developed at NIU Institute for Neutron Therapy at Fermilab. These experiments were possible because of an enhanced fast neutron therapy assembly designed to use the fast neutron beam at Fermilab to deliver a neutron beam containing a greater fraction of thermal neutrons and because of the development of improved calculations for dose for the enhanced neutron beam. Clonogenic response was determined. RESULTS: U87 cell survival after gamma irradiation, fast neutron irradiation and irradiation with the enhanced neutron beam in the presence or absence of Magnevist were determined. CONCLUSIONS: U87 cells were the least sensitive to gamma radiation, and increasingly sensitive to fast neutron irradiation, irradiation with the enhanced neutron beam and finally a significant enhancement in cell killing was observed for U87 cells preloaded with Magnevist. The sensitivity of U87 cells pre-loaded with Magnevist and then irradiated with the enhanced neutron beam can at least in part be attributed to the Auger electrons emitted by the neutron capture event.
