Secondary carcinogenesis in patients treated with radiation: a review of data on radiation-induced cancers in human, non-human primate, canine and rodent subjects

Concern for risk of radiation-induced cancer is growing with the increasing number of cancer patients surviving long term. This study examined data on radiation transformation of mammalian cells in vitro and on the risk of an increased cancer incidence after irradiation of mice, dogs, monkeys, atomic bomb survivors, occupationally exposed persons, and patients treated with radiation. Transformation of cells lines in vitro increased linearly with dose from approximately 1 to approximately 4-5 Gy. At <0.1 Gy, transformation was not increased in all studies. Dose-response relationships for cancer incidence varied with mouse strain, gender and tissue/organ. Risk of cancer in Macaca mulatta was not raised at 0.25-2.8 Gy. From the atomic bomb survivor study, risk is accepted as increasing linearly to 2 Sv for establishing exposure standards. In irradiated patients, risk of cancer increased significantly from 1 to 45 Gy (a low to a high dose level) for stomach and pancreas, but not for bladder and rectum (1-60 Gy) or kidney (1-15 Gy). Risk for several organs/tissues increased substantially at doses far above 2 Gy. There is great heterogeneity in risk of radiation-associated cancer between species, strains of a species, and organs within a species. At present, the heterogeneity between and within patient populations of virtually every parameter considered in risk estimation results in substantial uncertainty in quantification of a general risk factor. An implication of this review is that reduced risks of secondary cancer should be achieved by any technique that achieved a dose reduction down to approximately [corrected] 0.1 Gy, i.e. dose to tissues distant from the target. The proportionate gain should be greatest for dose decrement to less than 2 Gy.     

The dynamic content of prostaglandins and cyclic nucleotides in the blood of irradiated dogs and monkeys

In experiments with dogs and monkeys a study was made of the dynamics of the content of prostaglandins (PG) and cyclic nucleotides after gamma irradiation. In dogs irradiation with lethal doses (3.1 and 50 Gy) caused a short-term, evidently stress growth of cAMP, PGE and PGF2 alpha levels. At the height of radiation sickness PGF2 alpha and cGMP content decreased considerably. Irradiation of monkeys with a nonlethal dose of 3.2 Gy changed PGE and PGF2 alpha levels to a lesser extent, while concentrations of cyclic nucleotides varied but their ratio remained stable.     

Postoperative cataract cases among atomic bomb survivors: radiation dose response and threshold

Recent evidence argues against a high threshold dose for vision-impairing radiation-induced cataractogenesis. We conducted logistic regression analysis to estimate the dose response and used a likelihood profile procedure to determine the best-fitting threshold model among 3761 A-bomb survivors who underwent medical examinations during 2000-2002 for whom radiation dose estimates were available, including 479 postoperative cataract cases. The analyses indicated a statistically significant dose-response increase in the prevalence of postoperative cataracts [odds ratio (OR), 1.39; 95% confidence interval (CI), 1.24-1.55] at 1 Gy, with no indication of upward curvature in the dose response. The dose response was suggestive when the restricted dose range of 0 to 1 Gy was examined. A nonsignificant dose threshold of 0.1 Gy (95% CI, <0-0.8) was found. The prevalence of postoperative cataracts in A-bomb survivors increased significantly with A-bomb radiation dose. The estimate (0.1 Gy) and upper bound (0.8 Gy) of the dose threshold for operative cataract prevalence was much lower than the threshold of 2-5 Gy usually assumed by the radiation protection community and was statistically compatible with no threshold at all.     

Effects of single gamma-irradiation on the activity of ornithine decarboxylase in the thymus and pulmonary tissue]

In studying the dose (0.1-6 Gy) and time (2 h to 180 days) dependence of ornithine decarboxylase activity, it was found that deviations from the control were more pronounced in the thymus than in the pulmonary tissue. The radiation effect was a function of dose and time after irradiation. A nonmonotonous type of the dose-response curve was observed 7 days after irradiation: the radiation effect with a low dose (0.1 Gy) was opposite to that with sublethal doses (1-6 Gy).     

重组人血小板生成素早期干预救治重症急性放射病猴的实验研究

重组人血小板生成素（rhTPO）是一种能促进巨核系祖细胞增殖、分化生成血小板的造血因子,研究表明它能促进射线照射小鼠造血功能恢复,前期工作证明rhTPO早期干预可显著提高致死剂量照射小鼠的活存率.本文以7.0Gy照射恒河猴为重度骨髓型急性放射病（ARS）模型,研究了rhTPO早期干预对重症ARS的治疗作用,并与WR2721和＂500＂的辐射防护作用进行了比较,结果发现rhTPO早期干预可明显促进ARS猴造血功能恢复,改善ARS猴症状,简化对症治疗措施,提高重度骨髓型ARS猴活存率,其对重度骨髓型ARS的防治作用优于现有的辐射防护药WR2721和＂500＂,有望开发成安全有效的新型辐射防治药物.     

Long-term mutagenic effect in various types of somatic cells in monkeys exposed to low doses of penetrating radiation

High level of chromosome aberrations has been determined in different types of somatic cells of monkeys which were subjected to general daily repeated low-capacity radiation (0.049-0.0078 Gy per a day) and accumulated summary doses of about 8.26-36.77 Gy. Long persistence of cytogenetic irradiation aftereffect (15-19 years of observation) has been shown. Differences are revealed in the frequency and types of chromosome aberrations in tissues with different level of cell proliferation: in bone marrow, peripheral blood lymphocytes and epithelial renal cells of irradiated monkeys.     

Apoptosis in HeLa Hep2 cells is induced by low-dose,low-dose-rate radiation

Radioimmunotherapy with radiolabeled antibodies may cause inhibition of the growth of epithelial tumors, despite low total radiation doses and comparatively low radiosensitivity of epithelial tumor cells. The induction of apoptosis by low-dose radiation, such as delivered in radioimmunotherapy, was investigated in vitro in human HeLa Hep2 carcinoma cells. The cultured cells were exposed to defined radiation doses from a (60)Co radiation therapy source. The radiation source delivered 0.80 +/- 0.032 (mean +/- SD) Gy/min and the cells were given total doses of 1, 2, 5, 10 and 15 Gy. Using fluorescein-labeled Annexin V, followed by flow cytometry and DNA ladder analysis, apoptotic cells were detected and quantified. Radiation doses below 2 Gy did not cause any significant increase in apoptosis. Compared to control cells, apoptosis was pronounced after 5-10 Gy irradiation and was correlated to the radiation dose, with up to 42 +/- 3.5% of the cells examined displaying apoptosis. Clonogenic assays confirmed significantly decreased viability of the cells in the interval 2 to 10 Gy with low-dose-rate radiation, 60 +/- 2% compared to 2 +/- 2%. Lethal effects on the tumor cells were also evaluated by an assay of the cytotoxic effects of the release of (51)Cr. Significant cytotoxicity, with up to 64 +/- 6% dead cells, was observed at 5 Gy. Similar results were obtained when the dose rate was reduced to 0.072 +/- 0.003 Gy/min (mean +/- SD). In the case of the (137)Cs source, the dose rate could be reduced to 0.045 Gy/h, a level comparable to radioimmunotherapy, which induced significant apoptosis, and was most pronounced at 72-168 h postirradiation. It can be concluded that in vitro low-dose and low-dose-rate radiation induces apoptosis in epithelial HeLa Hep2 cells and thus may explain a mechanism by which pronounced inhibition of growth of HeLa Hep2 tumors at doses used in radioimmunotherapy has been obtained previously.     

Estimation of the influence of physical and biological factors on the development of the hematopoietic type of radiation sickness in dogs and two types of monkeys

In this investigation, the analysis of radiobiological experiments on 532 dogs and two types of monkeys (101 animals), irradiated totally in the 1.0 to 6.0 Gy dose range at different irradiation facilities, has been carried out. LD50 values at X-ray and gamma-neutron exposure were close to each other (2.35 and 2.83 Gy, respectively) while at gamma-radiation exposure LD(50/45) increased to 3.09 Gy. Comparison of LD(50/45) values for different kinds of animals allowed us to draw a conclusion of approximately equal radiosensitivities of dogs and Macaca fascicularis monkeys (LD(50/30-45) - 3.09 Gy and 3.17 Gy, respectively); Macaca rhesus monkeys revealed higher radioresistance (LD(50/30-45) - 5.03Gy). Analysis of the influence of several biological factors has not displayed any significant differences in the values of LD(50/45) and average lifespan of male and female dogs. Higher radiosensitivity of dogs with body weight less than 12 kg and lower radiosensitivity of dogs in summer time compared to other seasons have been shown. Dogs at the age of 2 to 3 years appeared to be more radioresistant than animals of the other age.     

Effects of prolonged low-intensity irradiation on organ weight of the male rat reproductive system

The effects of prolonged irradiation at accumulated doses from 0.5 to 6.0 Gy (dose rate 3.03 cGy/day) on reproductive organs' weight (testes, epididymises, seminal vesicles, prostate) of male rats starting from the early ontogenetic period were studied. On the first day after the irradiation with 1.0 Gy dose a significant loss of the weight in testes and epididymises was revealed. This leaded to the marked atrophy of the organs with the increase of the radiation dose. Long-term restoration of the weight of testes and epididimyses was registered. It was not completed during three months after radiation exposure at 2.0 Gy and higher doses for epididimyses and 4.0-6.0 Gy for testes. The respective changes in the seminal vesicles and prostate weight were less pronounced and had more complicated character. However in the distant period (30-90 days of postreatment) after exposure to 2.0 Gy these parameters were noticeably decreased.     

The effects of ionizing radiation on the pulmonary vasculature of intact rats and isolated pulmonary endothelium

We studied the effects of ionizing radiation on the morphology of the pulmonary circulation using an in vivo rat model and an in vitro pulmonary artery endothelial cell model. Gamma radiation was given as either an acute (30 Gy) or fractionated (5 X 6 Gy) dose to one hemithorax of rats. An acute 30-Gy dose delivered resulted in a 70% decrease in pulmonary arterial perfusion, using technetium-99m microaggregated albumin (99mTc-MAA), in the irradiated lung by 2-3 weeks after irradiation. Pulmonary microradiographs, using a barium sulfate perfusion method, obtained 2-3 weeks after irradiation demonstrated widespread loss of capillary filling and segmentation of the vessels. Histologic examination demonstrated intact capillaries, suggesting that the alterations in pulmonary perfusion were at the precapillary level. Similar abnormalities in lung perfusion and morphology were found after delivery of fractionated doses of radiation, but the onset of the changes was delayed, occurring 4-6 weeks postirradiation. Using cultured pulmonary endothelial cell monolayers, cell sloughing and retraction from the surface substrate were observed within 24 h after in vitro delivery of 30 Gy. Similar findings occurred in monolayers given fractionated doses (5 X 6 Gy) of radiation 2-3 days after the final dose. The in vivo animal and in vitro endothelial cell models offer a useful means of examining the morphologic alterations involved in radiation lung vascular damage.     

Associations of ionizing radiation and breast cancer-related serum hormone and growth factor levels in cancer-free female A-bomb survivors

Levels of exposure to ionizing radiation are increasing for women worldwide due to the widespread use of CT and other radiologic diagnostic modalities. Exposure to ionizing radiation as well as increased levels of estradiol and other sex hormones are acknowledged breast cancer risk factors, but the effects of whole-body radiation on serum hormone levels in cancer-free women are unknown. This study examined whether ionizing radiation exposure is associated with levels of serum hormones and other markers that may mediate radiation-associated breast cancer risk. Serum samples were measured from cancer-free women who attended biennial health examinations with a wide range of past radiation exposure levels (N = 412, ages 26-79). The women were selected as controls for separate case-control studies from a cohort of A-bomb survivors. Outcome measures included serum levels of total estradiol, bioavailable estradiol, testosterone, progesterone, prolactin, insulin-like growth factor-1 (IGF1), insulin-like growth factor-binding protein 3 (IGFBP-3), and ferritin. Relationships were assessed using repeated-measures regression models fitted with generalized estimating equations. Geometric mean serum levels of total estradiol and bioavailable estradiol increased with 1?Gy of radiation dose among samples collected from postmenopausal women (17%(1Gy), 95% CI: 1%-36% and 21%(1Gy), 95% CI: 4%-40%, respectively), while they decreased in samples collected from premenopausal women (-11%(1Gy), 95% CI: -20%-1% and -12%(1Gy), 95% CI: -20%- -2%, respectively). Interactions by menopausal status were significant (P = 0.003 and P < 0.001, respectively). Testosterone levels increased with radiation dose in postmenopausal samples (30.0%(1Gy), 95% CI: 13%-49%) while they marginally decreased in premenopausal samples (-10%(1Gy), 95% CI: -19%-0%) and the interaction by menopausal status was significant (P < 0.001). Serum levels of IGF1 increased linearly with radiation dose (11%(1Gy), 95% CI: 2%-18%) and there was a significant interaction by menopausal status (P = 0.014). Radiation-associated changes in serum levels of estradiol, bioavailable estradiol, testosterone and IGF1 were modified by menopausal status at the time of collection. No associations with radiation were observed in serum levels of progesterone, prolactin, IGFBP-3 or ferritin.     

Neutron RBE for primate spinal cord treated with clinical regimens.

The RBEs of high-energy neutrons given in 9 or 12 fractions for cervical spinal cord injury in rhesus monkeys was determined using photons at 2.2 Gy per fraction as the reference radiation. Because the dose-response functions were not parallel, the RBE was not constant but rather increased with dose or, equivalently, with the probability of myelopathy. This required the development of a novel method of determining the RBE versus level of response. The RBE is presented as a function of probability of myelopathy from 0.1 to 99%. At a 50% incidence of myelopathy, the RBE (+/- 1 SE) was 5.22 +/- 0.15. A difference in the histopathology of lesions induced by photon and neutron treatments was observed.     

HemaMax™, a recombinant human interleukin-12, is a potent mitigator of acute radiation injury in mice and non-human primates

HemaMax, a recombinant human interleukin-12 (IL-12), is under development to address an unmet medical need for effective treatments against acute radiation syndrome due to radiological terrorism or accident when administered at least 24 hours after radiation exposure. This study investigated pharmacokinetics, pharmacodynamics, and efficacy of m-HemaMax (recombinant murine IL-12), and HemaMax to increase survival after total body irradiation (TBI) in mice and rhesus monkeys, respectively, with no supportive care. In mice, m-HemaMax at an optimal 20 ng/mouse dose significantly increased percent survival and survival time when administered 24 hours after TBI between 8-9 Gy (p<0.05 Pearson's chi-square test). This survival benefit was accompanied by increases in plasma interferon-γ (IFN-γ) and erythropoietin levels, recovery of femoral bone hematopoiesis characterized with the presence of IL-12 receptor β2 subunit-expressing myeloid progenitors, megakaryocytes, and osteoblasts. Mitigation of jejunal radiation damage was also examined. At allometrically equivalent doses, HemaMax showed similar pharmacokinetics in rhesus monkeys compared to m-HemaMax in mice, but more robustly increased plasma IFN-γ levels. HemaMax also increased plasma erythropoietin, IL-15, IL-18, and neopterin levels. At non-human primate doses pharmacologically equivalent to murine doses, HemaMax (100 ng/Kg and 250 ng/Kg) administered at 24 hours after TBI (6.7 Gy/LD(50/30)) significantly increased percent survival of HemaMax groups compared to vehicle (p<0.05 Pearson's chi-square test). This survival benefit was accompanied by a significantly higher leukocyte (neutrophils and lymphocytes), thrombocyte, and reticulocyte counts during nadir (days 12-14) and significantly less weight loss at day 12 compared to vehicle. These findings indicate successful interspecies dose conversion and provide proof of concept that HemaMax increases survival in irradiated rhesus monkeys by promoting hematopoiesis and recovery of immune functions and possibly gastrointestinal functions, likely through a network of interactions involving dendritic cells, osteoblasts, and soluble factors such as IL-12, IFN-γ, and cytoprotectant erythropoietin.     

Effects of recombinant human interleukin 11 on thrombocytopenia and neutropenia in irradiated rhesus monkeys

The effects of recombinant human interleukin 11 (rhIL11) on thrombocytopenia and neutropenia in irradiated rhesus monkeys were evaluated after administration different doses at different times. Twenty-three rhesus monkeys were exposed to a total-body irradiation (TBI) with a single dose of 3 Gy 60Co gamma rays. Either placebo, rhIL11 at a dose of 30, 60 or 120 microg/kg day(-1) on days 0-13, or rhIL11 at a dose of 60 microg/kg day(-1) on days 13-26 after TBI was administered to the animals. The results showed that the immediate treatment with rhIL11 but not treatment on days 13-26 resulted in much higher platelet nadirs than in the placebo-treated group. The accelerated recovery of platelets to normal levels after TBI was demonstrated in all groups treated with rhIL11, but the effects of rhIL11 were independent of dose. However, rhIL11 treatment could also accelerate the recovery of leukocytes to normal levels. The numbers of colony-forming bone marrow cells (CFU-E, CFU-Mix, CFU-MK and CFU-GM) in all groups treated with rhIL11 were increased 4- to 14-fold relative to those of the placebo group on day 30. We conclude that rhIL11 may directly promote megakaryocyte development and ameliorate myelosuppression in irradiated monkeys.     

Response of human fibroblasts to low dose rate gamma irradiation

Cells from 11 human strains, including fibroblasts from patients with the genetic diseases of ataxia telangiectasia (AT), xeroderma pigmentosum (XP), and Fanconi's anemia (FA), were exposed to gamma radiation at high (1.6-2.2 Gy/min) and at low (0.03-0.07 Gy/min) dose rates. Survival curves reveal an increase in the terminal slope (D0) when cells are irradiated at low dose rates compared to high dose rates. This was true for all cell lines tested, although the AT, FA, and XP cells are reported or postulated to have radiation repair deficiencies. From the response of these cells, it is apparent that radiation sensitivities differ; however, at low dose rate, all tested human cells are able to repair injury.     

The significance of cytogenetic investigation for the estimation of Chernobyl accident consequences

The results of the cytogenetic investigation of people, which were exposed to radiation in the result of the Chernobyl NPP accident, were presented. Also the possibilities of the application of cytogenetic findings for dose estimations and for the prediction of the radiation influence consequences were examined. During the period of time since 1986 till 2004 the cytogenetic investigations of 1724 liquidators participating in the liquidation works after the Chernobyl accident were carried out. The radiation dose estimated by the frequency of dicentrics in 1986 was about 0.16 Gy. The doses for liquidators were determined by the frequency of translocations (FISH method) during the period from 1992 till 1995. For liquidators who worked in Chernobyl only in 1986 the average dose of radiation was about 0.19 Gy and for liquidators who worked repeatedly during the period from 1986 till 1995 - 0.39 Gy. There was shown that during the whole period of investigation (1986-2004) the frequency of dicentrics in peripheral blood lymphocytes was significantly higher than the control level. The cytogenetic investigation of Bryansk region inhabitants which was carried out in 1992-1994 discovered heightened value in 5 times than the control one. Findings are of great importance for the prediction of ill effects of radiation and for the development of sensitive criterions for early exposure disturbances in state of health.     

A dose-effect relationship study for the frequency of binuclear cells with micronuclei in a human lymphocyte culture after gamma irradiation

The method of the cytokinetic blocking was used to determine, in 18 healthy male donors aged 21-35 years, the frequency of binuclear cells with micronuclei that amounted to 1.1 +/- 0.2% (0.3-2.4%) on the average. The dependence of this parameter upon radiation dose (60Co-gamma radiation, 0.05 to 2 Gy) was a linear quadratic function and was described by the following regression equation: Yx = 0.76 + 5.76 D +/- 2.61 D2. With a dose of 0.05 Gy the frequency of binuclear cells with micronuclei exceeded significantly the control level.     

Changes in synapses after gamma-irradiation of the rat head

High reactivity and, at the same time, flexibility of interneuronal contacts were observed after exposure of rat head to 2-100 Gy radiation. At high doses (200-400 Gy) radiation-induced changes played a major role in the development of the cerebral form of radiation sickness. A complete asynapsis is probably one of the causes of the animals death "under the ray" (irradiation of the head with a dose of 1000 Gy).     

A fluorescence approach of the gamma radiation effects on gramicidin A inserted in liposomes.

The fluorescence of tryptophan residues of gramicidin A (gA), bound to phosphatidylcholine liposomes contains valuable information about local changes in the environment of the molecule induced by gamma radiation. With this work, we aim to demonstrate that the gamma radiation effect on the peptide involves the action of free radicals, derived from water radiolysis and the process of lipid peroxidation. Basically, the methodology consists of the analysis of UV and fluorescence emission spectra of the peptide liposome complexes under control conditions and upon gamma irradiation. Free radical production was impaired by the removal of molecular oxygen or the presence of ethanol in the liposome suspension. The intensity of the tryptophan fluorescence was recorded as a function of the gamma radiation dose in the range of 0-250 Gy and the data were fitted with a single decay exponential function containing an additional constant term (named residual fluorescence). The correlation between the decrease in tryptophan fluorescence emission (D(c) = 80 +/- 10 Gy) and increase in gamma radiation dose indicates the partial damage of the tryptophan side chains of gA. O(2) removal or ethanol addition partially reduced the decay of the tryptophan fluorescence emission involving an indirect action of gamma radiation via a water radiolysis mechanism. The residual fluorescence emission (A(0)) increases in O(2)-free buffer (98 +/- 13) and in 10% ethanol-containing buffer (74 +/- 34) compared to control conditions (23 +/- 5). Varying the dose rate between 1-10 Gy/min at a constant dose of 50 Gy, an inverse dose-rate effect was observed. Thus, our study provides evidence for the lipid peroxidation effect on the tryptophan fluorescence. In conclusion, this article sustains the hypothesis of the connection between the lipid peroxidation and structural changes of membrane proteins induced by gamma radiation. Copyright (c) 2008 European Peptide Society and John Wiley & Sons, Ltd.