Ortmann, E. K., Mayerhofer, T., Getoff, N. and Kodym, R. Effect of Antioxidant Vitamins on Radiation-Induced Apoptosis in Cells of a Human Lymphoblastic Cell Line. Radiat. Res. 161, 48–55 (2004).Modulating the amount of radiation-induced apoptosis by administering antioxidant vitamins offers a possible way to influence radiation-induced side effects in normal tissues. Therefore, we investigated the effect of beta-carotene, vitamin C and alpha-tocopherol on radiation-induced apoptosis in cells in culture. Human T-lymphoblastic MOLT-3 cells were irradiated with a dose of 3 Gy 1 h after or immediately prior to the addition of vitamins in three concentrations (0.01 μM, 1 μM and 100 μM). Eight hours later, apoptosis was scored morphologically by staining the nuclear DNA with Hoechst 33342. When given prior to irradiation, beta-carotene and vitamin E reduced the amount of radiation-induced apoptosis significantly at concentrations of 0.01 μM and 1 μM. In contrast, vitamin C did not show any protective effect when given at these two concentrations and caused a slight but significant radiosensitization at 100 μM. At 0.01 μM, all combinations of two vitamins showed a protective effect. This was also observed for the combination of all three vitamins at concentrations of 0.01 and 1 μM. When given immediately after irradiation, each of the three vitamins showed a protective effect at 0.01 μM. In addition, the combination of alpha-tocopherol and vitamin C reduced radiation-induced apoptosis slightly when given at 1 μM. In all other cases, no statistically significant modulation of radiation-induced apoptosis was observed. In our experimental system, the protective effect of beta-carotene and vitamin E was dependent on concentration and occurred only in the micromolar and sub-micromolar concentration range, while vitamin C alone, but not in combinations, had a sensitizing effect, thus arguing for a careful consideration of vitamin concentrations in clinical settings.
Understanding the damage of DNA bases from hydrogen abstraction by free OH radicals is of particular importance to reveal the effect of hydroxyl radicals produced by the secondary effect of radiation. Previous studies address the problem with truncated DNA bases as ab-initio quantum simulation required to study such electronic spin dependent processes are computationally expensive. Here, for the first time, we employ a multiscale and hybrid Quantum-Mechanical-Molecular-Mechanical simulation to study the interaction of OH radicals with guanine-deoxyribose-phosphate DNA molecular unit in the presence of water where all the water molecules and the deoxyribose-phosphate fragment are treated with the simplistic classical Molecular-Mechanical scheme. Our result illustrates that the presence of water strongly alters the hydrogen-abstraction reaction as the hydrogen bonding of OH radicals with water restricts the relative orientation of the OH-radicals with respective to the the DNA base (here guanine). This results in an angular anisotropy in the chemical pathway and a lower efficiency in the hydrogen abstraction mechanisms than previously anticipated for identical system in vacuum. The method can easily be extended to single and double stranded DNA without any appreciable computational cost as these molecular units can be treated in the classical subsystem as has been demonstrated here.
Retrospectively the patients were analyzed, postoperatively irradiated because of a hypernephroidal kidney carcinoma during the years 1978 to 1988. With a total number of 44 patients 12 were in stage I (Robson), 13 in stage II, 17 in stage III and 2 in stage IV. The probabilities for a tumor-free survival of five years were 81%, 59% and 30% for the stages I to III. The local recurrence rate was 7%, caused by exclusion of clinically negative lymph-nodes from irradiation field. In addition to survival probabilities the complication rate of radiotherapy is analyzed too. To this additionally to analysis of symptoms of a possible side-effect the nuclear medical investigation of function of the remaining kidney was done in 9 selected tumor-free patients being irradiated in different techniques. A normal function was found in all cases. No severe side-effects can be shown in irradiated patients. Consequently the postoperative radiotherapy in hypernephroma is a supportive therapy of advanced tumor stages without severe side-effects. Further and greater planned analyses are necessary to comprehend prognostic factors.
Erythropoietin is well known for its role in the control of erythropoiesis, where it acts by binding to its cognate receptor (EpoR) on the surface of erythroid progenitor cells. Here we present the novel finding that the EpoR is also expressed in cells of the melanocytic lineage. It is expressed in transformed cell lines established from normal melanocytes and also in established human melanoma cell lines derived from melanoma metastases, but not in normal primary human melanocytes. The analysis of individual subclones isolated from spontaneously transformed melanocytes revealed that approximately 50% of all the clones examined expressed the EpoR. Further analysis of the individual growth characteristics of EpoR-positive and EpoR-negative clones indicated that, under standard cell culture conditions, expression of the receptor did not affect cell growth. Expression of this receptor is consequently most likely driven by an event that is associated with, but not absolutely required for, the transformed phenotype. While the definite function of this receptor in melanoma cells is still unknown and additional studies are required, our findings support the hypothesis that the EpoR may serve as a progression marker for human melanoma. This observation might be useful in the early diagnosis of melanoma.
