Transformation and radiosensitivity of human diploid skin fibroblasts transfected with activated ras oncogene and SV40 T-antigen.

Three normal human diploid cell strains were transfected with an activated Ha-ras oncogene (EJ ras) or SV40 T-antigen. Multiple clones were examined for morphological alterations, growth requirements, ability to grow under anchorage independent conditions, immortality and tumorigenicity in nude mice. Clones expressing SV40 T-antigen alone or in combination with ras protein p21 were significantly radioresistant as compared with their parent cells or clones transfected with the neo gene only. This radioresistant phenotype persisted in post-crisis, immortalized cell lines. Cells transfected with EJ ras alone showed no morphological alterations nor significant changes in radiosensitivity. Cell clones expressing ras and/or SV40 T-antigen showed a reduced requirement for serum supplements, an increase in aneuploidy and chromosomal aberrations, and enhanced growth in soft agar as an early cellular response to SV40 T-antigen expression. The sequential order of transfection with SV40 T-antigen and ras influenced radio-sensitivity but not the induction of morphological changes. These data suggest that expression of the SV40 T-antigen but not activated Ha-ras plays an important role in the radiosensitivity of human diploid cells. The radioresistant phenotype in SV40 T transfected cells was not related to the enhanced level of genetic instability seen in pre-crisis and newly immortalized cells, nor to the process of immortalization itself.     

Studies on the influence of the presence of an activated ras oncogene on the in vitro radiosensitivity of human mammary epithelial cells.

The clonogenic cell survival to gamma-rays was determined in a human mammary epithelial cell line transfected by an activated ras oncogene in comparison to either the host untransfected cell line or the same cell line transfected by the neo gene. In contrast to previous observation of fibroblasts derived from a murine cellular system (NIH 3T3), the analysis of survival curves did not demonstrate an acquired radioresistance in the human ras transfected cells as opposed to the two other cell lines. In other words, the appearance of resistance to ionizing radiation does not seem to be a feature which can be generalized to all situations associated to activation of a specific oncogene (ras).     

The influence of ras oncogene expression on radiation response in the Rat-1 cell.

We evaluated the effect of H-ras oncogene expression on resistance to ionizing radiation in cultured rat fibroblasts. The Rat-1 cell line, and two Rat-1 derivatives, MR4 and MR7, carrying a ZN-regulatable metallothionein-rasT24 fusion gene were used to study the effects of the ras oncogene on radiation sensitivity. Cells were irradiated with a 137Cs source (450 cGY/min) in the presence or absence of ZnSO4. Multiple cell survival studies did not show an appreciable difference in sensitivity to radiation among the lines in the presence or absence of ras oncogene expression.     

The radiosensitivity of endometrial carcinoma.

An analysis of all cases (121) of endometrial carcinoma treated by pre-operative radium in the uterine cavity revealed that the menopausal status of a patient affects the radiosensitivity of her tumour. It was found that if the patient is more than ten years post-menopausal at time of diagnosis her carcinoma will be more resistant to radiation. The technique used by the authors is adequate in eradicating a considerable percentage (68%) of endometrial carcinomas.     

The radiosensitivity of a mesenchymal tissue. The pericryptal fibroblast sheath in the human rectal mucosa.

With the exception of haemopoietic tissue quantitative studies of the effects of irradiation on replicating normal tissue call systems in vivo have previoulsy been confined to epitelial tissuss. A similar sheath of fibroblasts to that surrounding the crypts of Lieberkühn in the colon, which it is climed undergoes constant renewal and migration, has now been identified in the rectum and thereby it may become possible to follow the cellular response to irradiation of a mesenchymal tissue. The numbers and the distribution of the pericrytal fibroblasts in normal human rectum following irradiation, both in air and hyperbaric oxyge, have been stuided in serial biopsies of rectal mucosa taken from patients who were being treated for advanced pelvic maliganancies. The results indicate that during a course of irradiation the fibroblasts cell count falls on a time-scale very closely associated with that seen in the epithelial cells. Only some immediate recovery occurs in the fibroblast system, in contrast to the adjacent epithelial cell system where full recovery seems to take place. The fibroblast system, moreover, shows a gradually diminishing trend during the first year, whilst the epithelial cell numbers appear to be maintained. The interpretation of these data are discussed. Evidence is provided that when patients breath hyperbaric oxygen during irradiation more extensive depression of cell numbers occurs, but after recovery there is essentially no difference in the cell counts - finding that accord with those previously reported fro epithelial cells in the crypts of the rectal mucosa.     

Chromosome radiosensitivity in human G2 lymphocytes and cell-cycle progression.

PURPOSE: To investigate the possibility that the differential G2-phase radiosensitivity of human peripheral blood lymphocytes, found in normal individuals using the 'G2-phase chromosome radiosensitivity assay', could be attributed to heterogeneity in cellular progression to mitosis rather than differences in radiosensitivity. MATERIALS AND METHODS: Human peripheral blood lymphocytes, from four different donors, were exposed to 50 cGy X-rays and sampled at different times. The progression of cells into mitosis was monitored by 5-bromo 2'-deoxyuridine (BrdUrd) incorporation. RESULTS: The heterogeneous G2-phase chromosome radiosensitivity among different donors was abolished when homogeneous G2-phase cell populations were scored; they contained similar frequencies of cells in early or late G2-phase. CONCLUSIONS: The heterogeneous G2-phase chromosome radiosensitivity, usually found in different normal donors, is caused by the analysis of different cell populations rather than reflecting intrinsic differences in radiosensitivity.     

沉默细胞周期检测点激酶1(Chk1)对宫颈癌HeLa细胞放射敏感性的影响

目的 探讨siRNA沉默细胞周期检测点激酶1（Chk1）基因对宫颈癌HeLa细胞放射敏感性的影响。方法 合成Chk1基因的小分子干扰RNA（si-Chk1）,将si-NC或者si-Chk1分别转染到宫颈癌HeLa细胞中,0、2、4、6、8、10 Gy剂量的X射线照射细胞,RT-qPCR和Western blot检测转染后Chk1的mRNA水平和蛋白水平的表达,MTT方法检测细胞增殖能力,流式细胞仪检测细胞凋亡,克隆形成实验检测转染后HeLa细胞放射敏感性,Western blot检测转染后P21蛋白和抗凋亡基因Bcl-2蛋白的表达水平。结果 si-Chk1转染到HeLa细胞后,HeLa细胞Chk1基因的mRNA和蛋白表达水平均显著下降（t=2.12~5.86,P<0.05）,沉默Chk1的表达抑制了宫颈癌HeLa细胞的增殖（t=3.15~6.36,P<0.05）,同时降低宫颈癌HeLa细胞克隆形成能力（t=1.58~6.36,P<0.05）,上调P21（t=4.35,P<0.05）、下调Bcl-2蛋白（t=2.37,P<0.05）的表达水平。结论 siRNA沉默Chk1表达能够增强HeLa细胞放射敏感性。     

The radiobiology of human cells and tissues. In vitro radiosensitivity. The picture has changed in the 1980s

Substantial developments have been made during the 1980s in the radiobiology of human tumours, in particular in studies of the radiosensitivity of human tumour cells. It is now clear that tumour cells differ considerably in radiosensitivity, to an extent that by itself is capable of explaining the clinical response of tumours to radiotherapy. There also is evidence that the radiosensitivity of human tumour cell lines to low radiation doses correlates with clinical experience. Irradiation at low dose rate amplifies the differences between cell lines. In conjunction with mathematical modelling, a study of the dose-rate effect also allows a distinction to be drawn between repairable and non-repairable damage. The differences seen between cell lines at low acute doses or low dose rates are associated with the non-repairable component. The most radiosensitive cell lines have a steep component of non-repairable damage and they give the impression of being recovery-deficient; this may, however, be incorrect for when evaluated at constant dose levels recovery is found to increase with increasing radiosensitivity. This leads to the view that recovery from radiation damage may reflect the amount of recoverable damage inflicted rather than the 'capacity' of the cells to recover.     

Inherent cellular radiosensitivity of human tumors of varying clinical curability.

It is well known that radiation therapy can be successfully used to cure or control some types of human tumors, while consistently failing in others. This has been ascribed to several factors including differences in the intrinsic sensitivity of the tumor cells and in their ability to recover from radiation damage. In this study, human tumor cells from an osteogenic sarcoma, a glioblastoma, and two medulloblastomas, as well as cells from human skin, were established in tissue culture, and the in vitrox x-ray survival and DNA repair parameters determined. No significant differences in either clonogenic survival or DNA strand rejoining ability could be detected among these human tumors or skin cells, despite the wide variability in their radiocurability in vivo. In addition, skin cell strains derived from patients exhibiting markedly sensitive or resistant skin reactions during fractionated radiotherapy showed no differences in survival characteristics from normal controls. It is therefore suggested that the wide range of radiocurabilities seen among various human tumors cannot be explained on the basis of inherent cellular factors responsible for the survival of tumor cells after x-irradiation.     

Comparative human cellular radiosensitivity: IV. The increased sensitivity of human neonatal cord blood lymphocytes to gamma-irradiation compared with lymphocytes from children and adults.

We have compared the gamma-irradiation survival of G0 peripheral blood lymphocytes from 18 neonatal cord blood samples in a cloning assay with results from 21 controls (age range 1-65 years and consisting of 20 adults and one child). Using mean inactivation dose as the discriminating parameter, the cord blood cells showed a significantly greater radiosensitivity (mean inactivation dose for pooled data = 1.54 Gy) than the normal controls (mean inactivation dose for pooled data = 1.90 Gy, p less than 0.001). These results confirm and extend earlier work suggesting that T-lymphocytes in newborn children are more radiosensitive than normal controls, and this may have implications for the radiation protection of the unborn child.     

The relationship between potentially lethal damage repair and intrinsic radiosensitivity of human cells

The intrinsic radiosensitivity of exponentially growing cells (exp) was compared to that of immediately plated plateau phase cells (ip) using published data on 60 human cell lines (27 fibroblast lines and 33 tumour cell lines). The values for alpha, D and S2 are not significantly different for the two groups; beta is significantly higher in ip cells. This produces a smaller alpha/beta ratio in ip cells than in exp cells. The influence of potentially lethal damage (PLD) repair was assessed by comparing the radiosensitivities of ip cells and plateau phase cells with delayed plating (dp). The published data for 81 human cell lines (48 fibroblasts and 33 tumour lines) were used. PLD repair was found to lead to a decrease in alpha and an increase in D and S2, whereas neither beta nor the alpha/beta ratio changed significantly. The relationship between PLD repair and intrinsic radiosensitivity was assessed by repair capacity and the repair ratio. The fitted relationship is a bell-shaped curve with a maximum at 2.2 Gy for repair capacity. The fitted curve predicts that repair capacity is zero at a D up of 0.28 Gy and at 4 Gy. Thus, PLD repair is a reasonable reflection of intrinsic radiosensitivity up to 2.2 Gy. Above 2.2 Gy, the relationship is reversed: the greater the radioresistance, the lower the PLD repair.