Radiosensitivity of V79 cells after alpha particle radiation at low doses

Datasets of in vitro clonogenic assays showing low dose hyper-radiosensitivity and induced radioresistance

Low dose hyper-radiosensitivity and induced radioresistance are primarily observed in surviving fractions of cell populations exposed to ionizing radiation, plotted as the function of absorbed dose. Several biophysical models have been developed to quantitatively describe these phenomena. However, there is a lack of raw, openly available experimental data to support the development and validation of quantitative models. The aim of this study was to set up a database of experimental data from the public literature. Using Google Scholar search, 46 publications with 101 datasets on the dose-dependence of surviving fractions, with clear evidence of low dose hyper-radiosensitivity, were identified. Surviving fractions, their uncertainties, and the corresponding absorbed doses were digitized from graphs of the publications. The characteristics of the cell line and the irradiation were also recorded, along with the parameters of the linear-quadratic model and/or the induced repair model if they were provided. The database is available in STORE^DB, and can be used for meta-analysis, for comparison with new experiments, and for development and validation of biophysical models.

Measurement(s)	surviving fraction of cells
Technology Type(s)	optical microscopy
Factor Type(s)	absorbed dose
Sample Characteristic - Organism	Homo sapiens • Chinese hamster • Rattus sp.
Sample Characteristic - Environment	cell culture

Hyper-radiosensitivity and induced radioresistance and bystander effects in rodent and human cells as a function of radiation quality

In the past two decades, a body of experimental evidences in vitro has shown the presence of a plethora of phenomena occurring after low-dose irradiation [including hypersensitivity and induced radioresistance (IRR), adaptive response, bystander effect (BE) and genomic instability], which might imply a non-linear behaviour of cancer risk curves in the low-dose region and question the validity of the linear no-threshold model for cancer risk assessment in such a dose region. In this framework, a systematic investigation have been undertaken on non-linear effects at low doses as a function of different radiation quality and cellular radiosensitivity and in terms of different biological end points. The present article reports the recent results on hyper-radiosensitivity and IRR and BE phenomena, in terms of clonogenic survival in V79 Chinese hamster cells and T98G human glioblastoma cells irradiated with protons and carbon ions with different energy, as a function of dose (and fluence).

ATR signaling cooperates with ATM in the mechanism of low dose hypersensitivity induced by carbon ion beam

Little work has been done on the mechanism of low dose hyper-radiosensitivity (HRS) and later appeared radioresistance (termed induced radioresistance (IRR)) after irradiation with medium and high linear energy transfer (LET) particles. The aim of this study was to find out whether ATR pathway is involved in the mechanism of HRS induced by high LET radiation. GM0639 cells and two ATM deficient/mutant cells, AT5BIVA and AT2KY were irradiated by carbon ion beam. Thymidine block technique was developed to enrich the G2-phase population. Radiation induced early G2/M checkpoint was quantitatively assess with dual-parameter flow cytometry by detecting the cells positive for phospho-histone H3. The involvement of ATR pathway in HRS/IRR response was detected with pretreatment of specific inhibitors prior to carbon ion beam. The link between the early G2/M checkpoint and HRS/IRR under carbon ion beam was first confirmed in GM0639 cells, through the enrichment of cell population in G2-phase or with Aurora kinase inhibitor that attenuates the transition from G2 to M phase. Interestingly, the early G2/M arrest could still be observed in ATM deficient/mutant cells with an effect of ATR signaling, which was discovered to function in an LET-dependent manner, even as low as 0.2Gy for carbon ion radiation. The involvement of ATR pathway in heavy particles induced HRS/IRR was determined with the specific ATR inhibitor in GM0639 cells, which affected the HRS/IRR occurrence similarly as ATM inhibitor. These data demonstrate that ATR pathway may cooperate with ATM in the mechanism of low dose hypersensitivity induced by carbon ion beam.

High survival of frozen cells irradiated with gamma radiation

Cell storage in liquid nitrogen (LN) offers the most secure method of cell preservation even if cryopreserved cells are exposed to natural background of ionising radiation (IR). A lot of experiments have demonstrated that IR can induce damages in living cells, but only a little information regarding the response of cryopreserved cells is available. To investigate the effect of IR on frozen and unfrozen cells, peripheral blood mononuclear cells were directly irradiated at room temperature, then immediately frozen, or frozen and then irradiated in LN with different doses of gamma rays. After thawing, cells were incubated and death fraction was evaluated at different time points. Interestingly, the percentages of dead cells induced by IR gradually increased with both dose radiation and incubation time and were significantly lower for cells irradiated at -196°C than those irradiated at room temperature.