The Genotoxic and Pro-Apoptotic Activities of Advanced Glycation End-Products (MAGE) Measured with Micronuclei Assay Are Inhibited by Their Low Molecular Mass Counterparts.

An association between the cancer invasive activities of cells and their exposure to advanced glycation end-products (AGEs) was described early in some reports. An incubation of cells with BSA-AGE (bovine serum albumin-AGE), BSA-carboxymethyllysine and BSA-methylglyoxal (BSA-MG) resulted in a significant increase in DNA damage. We examined the genotoxic activity of new products synthesized under nonaqueous conditions. These were high molecular mass MAGEs (HMW-MAGEs) formed from protein and melibiose and low molecular mass MAGEs (LMW-MAGEs) obtained from the melibiose and N-α-acetyllysine and N-α-acetylarginine. We have observed by measuring of micronuclei in human lymphocytes in vitro that the studied HMW-MAGEs expressed the genotoxicity. The number of micronuclei (MN) in lymphocytes reached 40.22 ± 5.34 promille (MN/1000CBL), compared to 28.80 ± 6.50 MN/1000 CBL for the reference BSA-MG, whereas a control value was 20.66 ± 1.39 MN/1000CBL. However, the LMW-MAGE fractions did not induce micronuclei formation in the culture of lymphocytes and partially protected DNA against damage in the cells irradiated with X-ray. Human melanoma and all other studied cells, such as bronchial epithelial cells, lung cancer cells and colorectal cancer cells, are susceptible to the genotoxic effects of HMW-MAGEs. The LMW-MAGEs are not genotoxic, while they inhibit HMW-MAGE genotoxic activity. With regard to apoptosis, it is induced with the HMW-MAGE compounds, in the p53 independent way, whereas the low molecular mass product inhibits the apoptosis induction. Further investigations will potentially indicate beneficial apoptotic effect on cancer cells.

Energy dependence of radiochromic dosimetry films for use in radiotherapy verification.

AIM: The purpose of the study was to examine the energy dependence of Gafchromic EBT radiochromic dosimetry films, in order to assess their potential use in intensity-modulated radiotherapy (IMRT) verifications. MATERIALS AND METHODS: The film samples were irradiated with doses from 0.1 to 12 Gy using photon beams from the energy range 1.25 MeV to 25 MV and the film response was measured using a flat-bed scanner. The samples were scanned and the film responses for different beam energies were compared. RESULTS: A high uncertainty in readout of the film response was observed for samples irradiated with doses lower than 1 Gy. The relative difference exceeds 20% for doses lower than 1 Gy while for doses over 1 Gy the measured film response differs by less than 5% for the whole examined energy range. The achieved uncertainty of the experimental procedure does not reveal any energy dependence of Gafchromic EBT film response in the investigated energy range. CONCLUSIONS: Gafchromic EBT film does not show any energy dependence in the conditions typical for IMRT but the doses measured for pre-treatment plan verifications should exceed 1 Gy.

[Dose rate-dependent cellular and molecular effects of ionizing radiation]. / Wplyw mocy dawki na komórkowe, biochemiczne i molekularne efekty promieniowania jonizujacego.

The aim of radiation therapy is to kill tumor cells while minimizing damage to normal cells. The ultimate effect of radiation can be apoptotic or necrotic cell death as well as cytogenetic damage resulting in genetic instability and/or cell death. The destructive effects of radiation arise from direct and indirect ionization events leading to peroxidation of macromolecules, especially those present in lipid-rich membrane structures as well as chromatin lipids. Lipid peroxidative end-products may damage DNA and proteins. A characteristic feature of radiation-induced peroxidation is an inverse dose-rate effect (IDRE), defined as an increase in the degree of oxidation(at constant absorbed dose) accompanying a lower dose rate. On the other hand, a low dose rate can lead to the accumulation of cells in G2, the radiosensitive phase of the cell cycle since cell cycle control points are not sensitive to low dose rates. Radiation dose rate may potentially be the main factor improving radiotherapy efficacy as well as affecting the intensity of normal tissue and whole-body side effects. A better understanding of dose rate-dependent biological effects may lead to improved therapeutic intervention and limit normal tissue reaction. The study reviews basic biological effects that depend on the dose rate of ionizing radiation.

Correlation between radioactivity induced inside the treatment room and the undesirable thermal/resonance neutron radiation produced by linac.

High-energy therapeutic beams used in the radiotherapy induce photonuclear and electronuclear reactions which are accompanied by generation of undesirable radioisotopes and neutrons inside the treatment room. These neutrons at thermal and resonance energies induce nuclear reactions through the whole accelerator bunker. In consequence various radioisotopes emitting high-energy photons appear. In this paper the correlation between radioactivity induced inside the treatment room and the undesirable thermal and resonance neutron radiation generated by the therapeutic accelerator X-rays was studied. The thermal and resonance neutron fluence determined in chosen places inside the bunkers was 1.0x10(5)-3.4x10(5)cm(-2)Gy(-1) and 1.0x10(5)-1.6x10(6)cm(-2)Gy(-1) at thermal energies (<0.1eV) and 3.9x10(4)-1.3x10(5)cm(-2)Gy(-1) and 1.0x10(5)-1.1x10(6)cm(-2)Gy(-1) at epithermal energies (0.1eV-10keV), for the 15MV and 20MV beams, respectively. The gamma energy spectra measured inside the accelerator bunker depended on the neutron radiation level. The net count rates of the gamma peaks from the decays of the excited state (56)Fe* and (28)Si*, the result of the simple capture of the neutron, for the 20MV beam were almost one order of magnitude greater than those for the 15MV beam. Moreover, it turned out that the activation of the wedge - the main accelerator accessory was caused by neutrons.

Multiple bystander effect of irradiated megacolonies of melanoma cells on non-irradiated neighbours.

The multicellular megacolonies of human melanoma Me45 line growing on one part of the bottom of culture flasks were irradiated with 5 Gy (60Co), whereas megacolonies growing on the second part of the bottom were shielded. The bystander effect of radiation-traversed cells on non-traversed cells was studied during postradiation co-cultivation. Activity of superoxide dismutase (Mn and CuZn subunits), glutathione peroxidase (GSH-Pox) and malondialdehyde (MDA) concentration as a biochemical markers of bystander effect were monitored for a period of 72 h. The DNA damage was measured by the comet assay. Micronucleus induction, mitotic index and cellular death as apoptosis or necrosis were simultaneously estimated, based on morphologic criteria. The bystander effect of irradiated cells on their neighbours was observed as a slight increase of MDA concentration, comparable decrease of GSH-Pox activity, and some fluctuation of mitochondrial and cytoplasmic isoenzymes of SOD. DNA strand breaks and rejoining measured by comet assay as mean tail length, demonstrated clearly the bystander effect for nontraversed radiation cells, additionally verified by tail moment. There was also a significant increase of micronucleation and apoptosis generated by radiation traversed cells in shielded neighbours. Furthermore, significantly higher increase of necrosis in shielded neighbour cells compared to radiation traversed cells was observed. Proliferative activity showed a suppression in both, radiation traversed and shielded neighbour cells in all measured time points. The behaviour of used parameters points to the radical nature of modificators secreted by radiation traversed cells inducing bystander toxic damage in shielded neighbour cells.