Possible carcinogenic effects of X-rays in a transgenerational study with CBA mice
U. Mohr4,
C. Dasenbrock1,
T. Tillmann,
M. Kohler1,
K. Kamino,
G. Hagemann,
G. Morawietz1,
E. Campo2,
M. Cazorla2,
P. Fernandez2,
L. Hernandez2,
A. Cardesa2 and
L. Tomatis3
Institut für Experimentelle Pathologie, Medizinische Hochschule Hannover, Carl-Neuberg-Straße 1, D-30625 Hannover, Germany,
1 Fraunhofer-Institut für Toxikologie und Aerosolforschung, Nikolai-Fuchs-Straße 1, D-30625 Hannover, Germany,
2 Departamento de Anatomia Patologica, Hospital Cliníc, Villaroel 170, E-8036 Barcelona, Spain and
3 Istituto per l'Infanzia, Via dell'Istria 65/1, I-34137 Trieste, Italy
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Abstract
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A lifetime experiment using 4279 CBA/J mice was carried out to investigate whether the pre-conceptual exposure of sperm cells to X-ray radiation or urethane would result in an increased cancer risk in the untreated progeny, and/or increased susceptibility to cancer following exposure to a promoting agent. The study consisted of four main groups, namely a control group (saline), a urethane group (1 mg/g body wt) and two X-ray radiation groups (1 Gy, 2 Gy). At 1, 3 and 9 weeks after treatment, the males of these four parental groups were mated with untreated virgin females. The offspring of each parental group was divided into two subgroups: one received s.c. urethane (0.1 mg/g body wt once) as a promoter, the other saline, at the age of 6 weeks. All animals were evaluated for the occurrence of tumours. K-ras oncogene and p53 tumour suppressor gene mutations were investigated in frozen lung tumour samples. The female offspring of male parents exposed to X-rays 1 week before their mating showed a trend towards a higher tumour incidence of the haematopoietic system than the F1 controls. In addition, a higher percentage of bronchiolo-alveolar adenocarcinomas in male offspring born to irradiated paternals mated 1 week after X-ray treatment points to a plausible increased sensitivity of post-meiotic germ cell stages towards transgenerational carcinogenic effects. On the other hand, no increased tumour incidence and malignancy were observed in the offspring born to irradiated paternals mated 3 and 9 weeks after X-ray treatment. Paternal urethane treatment 1, 3 and 9 weeks prior to conception did not result in significantly altered incidence or malignancy of tumours of the lung, liver and haematopoietic tissue in the offspring. K-ras mutations increased during tumour progression from bronchiolo-alveolar hyperplasia to adenoma. Codon 61 K-ras mutations were more frequent in lung tumours of urethane-promoted progeny from irradiated parents than from control parents. P53 mutations were absent from these lung alterations.
Abbreviations: DEN, diethylnitrosamine; H & E, haematoxylin and eosin; PCRRFLP, polymerase chain reactionrestriction fragment length polymorphism; SSCP, single-strand conformation polymorphism.
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Introduction
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It has been a subject for discussion for many years whether preconceptual parental exposure to some environmental or industrial chemicals as well as ionizing radiation leads to an increased tumour incidence in progeny of the exposed persons (19). Although many reports have described the existence of such an association, the unequivocal causality of the association could not be demonstrated (4,10). Indirect evidence that environmental and dietary factors that affect the parents and can influence the cancer risk of their progeny has been provided by some studies (11,12). The doubled frequency of germline mutations at human minisatellite loci among offspring of irradiated parents (13) after the Chernobyl accident, as well as the very high levels of base-pair substitution rates for the mitochondrial cytochrome b gene of free-living voles collected next to reactor 4 at Chernobyl (14), underlines the transgenerational cancer risk.
The epidemiological study of Gardner et al. (15,16) proposed, for the first time, a causal relationship between infant leukaemia and the exposure of their fathers to radiation in a nuclear plant, especially when the exposure was close to the time of conception. In addition, three cases of retinoblastoma in children whose maternal grandfathers worked at the same nuclear plant were reported (17). Even if this observation needs to be confirmed by other studies and has been challenged by some epidemiologists (1820), its importance and potential significance for humans is such that it warrants attention.
In the studies by Gardner et al. (15,16) and McLaughlin et al. (21) only tumours occurring during childhood and youth have been taken into consideration. The consequences of germ cell alterations might, however, be revealed in the offspring only following exposure to various environmental carcinogens and/or promoters during their lifetime. As a consequence, an increased risk of developing cancer may also be seen later in life, and in certain instances perhaps only then. There is also no valid reason to assume that the long-term effect of germ cell irradiation will only be expressed on the lymphopoietic system.
The possibility of germ cell transmission of an increased cancer risk following exposure to exogenous agents has been reported in several animal experiments. An increase of tumour incidence in progeny of parents exposed prior to conception to a number of carcinogenic factors, e.g. radiation (2224), 7,12-dimethylbenz[a]anthracene (25), N-ethylnitrosourea (26), urethane (27), diethylstibestrol (28), benzo[a]pyrene (29), etc., has been repeatedly described in laboratory animal models (for reviews see refs 8,30). Furthermore, there are several reports indicating that preconceptual exposure to a carcinogen/mutagen may result in an increased susceptibility to tumour promotion in the progeny (31,32).
The study reported here was begun with the purpose of providing indications as to whether and to what extent the exposure of the male parent to X-radiation or a chemical carcinogen/mutagen prior to conception may increase the cancer risk in progeny. The CBA/J mouse strain was considered suitable for this study because of its known moderate spontaneous tumour rate (18% lung tumours) (33).
X-rays are a human and experimental mutagen and carcinogen, and induce genetic damage in germ cells, which increases the frequency of congenital anomalies and of certain tumours (30,34). In the present experiment, X-ray irradiation was selected also because it allowed circumscribed local irradiation of the paternal gonads without affecting the whole body and because numerous experimental data of similar experiments exist (2224,27,35,36).
Urethane is one of the most widely studied carcinogens/promoters (33,3739) and was previously reported to be effective in multigenerational carcinogenesis studies (22,23,27,4042).
In our experiment, the F1 descendants from males, who were exposed prior to mating with untreated females, were divided into two groups: one was left untreated to observe the consequence of the preconceptual exposure per se and the other was exposed to a low dose of urethane. The latter group was intended to clarify whether the pre-zygotic exposure of the male parent had or had not modified the response of the F1 group to postnatal exposure to a chemical that is a carcinogen as well as a tumour promoter. This is of particular relevance, since humans are certainly exposed to a variety of promoters during their lifetime to the point that, in most instances, the exposure to promoters may represent the rate-limiting factor for human tumours. Thus, the study design fulfils the concept of multistage and multifactorial carcinogenesis, in which the preconceptual exposure to a carcinogen acts as an initiating event and postnatal exposure to promoting agents may be the stimulus to manifest the carcinogenic effects (43).
Apart from routine histopathological examinations, molecular biological analyses of the K-ras proto-oncogene mutations were performed using DNA from lung tumours as well as from normal lung tissues. Specific ras mutations have been revealed in several genetic loci of these oncogenes, and have been related both to the type of carcinogen used and to the tissue of origin of the tumour (44). Urethane, which was used in the experiment, is known to cause specific mutations in K-ras (4547). In addition the same lung samples were screened for inactivation mechanisms (mutations and deletions) of the p53 tumour suppressor genes. Alterations of p53 were observed in the sporadic form of most human tumours (48,49) and as a consequence of germ-line mutations in some cancer-prone families (4951).
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Materials and methods
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CBA/JNCrj mice (Charles River Deutschland, Sulzfeld, Germany) were housed under standard laboratory conditions: 1923°C, 4570% relative humidity, air change rate 15 times/h, 12:12 h lightdark cycle, three mice per polycarbonate cage (350 cm2), softwood bedding H3/4 (Hahn, Kronsberg, Germany), a pelleted maintenance diet 1324 (Altromin, Lage, Germany) and tap water ad libitum.
An X-ray generator for skin irradiation, type RT 100 (Philips, Hamburg, Germany) was used to irradiate the testicles of the mice. The tube potential was 100 kV, the tube current 8 mA. A standard filter of 1.7 mm aluminium and an additional filter of 0.2 mm copper achieved uniform penetration of the testicle tissue. For collimation of the X-ray beam, a copper tube of 300 mm in length and 80 mm in diameter was sealed with a 10 mm thick brass plate in the centre, of which a 15 mm wide and 20 mm long brass tube/cylinder was mounted. The brass tube/cylinder was sealed with a 1 mm thick plate of polystyrene in order to attenuate the weak scattering radiation. For uniform penetration of the testicles, the narcotized mice were fixed in a lateral position on an acrylic glass plate. For the dose measurements, a membrane chamber of the Dosimeter SN 4 with a 10 mm diameter was used (Physikalisch-Technische Werkstätten, Freiburg/Breisgau, Germany). An energy dose of 1 Gy yielded an irradiation time of 3 min 32 s. At deviations of ~2 mm from the pre-supposed tissue thickness of 8 mm, the corresponding dose variations were ~2.8%.
Urethane (CAS no. 51-79-6, product no. U2500, lot no. 092H0278, purity >99%) was purchased from Sigma (Deisenhofen, Germany). It was dissolved in saline (sterile 0.9% sodium chloride solution).
The study consisted of four main groups: the control group, the urethane group and two radiation groups (Figure 1
). All male parents were treated at 9 weeks of age. In the radiation groups the testicles of male parental mice were exposed to X-rays, under ketamine/xylazine narcosis, in two single doses of 0.5 and 1 Gy, respectively, alternating the (contralateral) side position of the animal at 24 h intervals, which resulted in total doses of 1 and 2 Gy. The urethane [two single subcutaneous (s.c.) doses of 0.5 mg/g body wt each at 24 h intervals] and control (0.01 ml/g body wt saline s.c.) treatments of the parental mice were carried out in a similar manner. At 1, 3 and 9 weeks after treatment, i.e. at different stages of spermatogenesis, the males were mated for 4 days each with three untreated, virgin 12-week-old females. At the age of 6 weeks, one half of all the offspring (F1) were treated once with 0.1 mg/g body wt urethane s.c. and the other half with saline s.c. (0.01 ml/g body wt). For clear animal identification, microchips (BioMedic Data Systems, Elst, The Netherlands) were implanted s.c. in all mice. The implantation of microchips was carried out in the parental mice at ~1619 weeks of age, and in the offspring at the age of 8 weeks, i.e. 12 weeks after the last treatment, mating or weaning.

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Fig. 1. Experimental design. S, saline; U, urethane; group identification according to Tables IIIV  of parentals: KP, UP, RP, RPA; and of offspring: KNi, KUi, UNi, UUi, RNi, RUi, RNAi, RUAi (i = 1, 3 and 9 week mating time-point).
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All 4279 animals (Table I
) were kept for their entire lifespan and evaluated for the occurrence of tumours. Complete autopsy was carried out on all mice. Any animal judged to be moribund was anaesthetized with an overdose of CO2, exsanguinated and necropsied. All animals found dead were necropsied immediately. Tissues for histological examination were fixed in 10% buffered formalin and embedded in Paraplast Plus (Sherwood Medical, St Louis, MO). Skulls and bones with macroscopic findings were decalcified with Ossa Fixona (Waldeck, Münster, Germany) prior to embedding. Embedded tissues to be examined histopathologically were sectioned (34 µm thick sections) and stained with haematoxylin and eosin (H & E; Lillie-Mayer method). In animals killed in a moribund condition, left lung lobes were placed in cryocups with Tissue-Tek OCT compound (Miles, Elkart, IN), shock-frozen in liquid nitrogen and stored at 80°C. Tumour diagnosis and classification followed WHO/IARC nomenclature (52).
K-ras oncogene and p53 tumour suppressor gene mutations were studied in 235 frozen matched normal and tumour samples of the lung. The analysis procedures are described in detail by Cazorla et al. (53). Briefly, normal tissue and tumours were microdissected after microscopic control of H & E-stained sections (Mayer's haematoxylin). DNA was extracted from the microdissected tissue and analysed. K-ras mutations were detected by a polymerase chain reactionrestriction fragment length polymorphism (PCRRFLP) technique. Two regions of K-ras gene containing codon 12/13 and codon 61 were amplified by PCR, and the amplified products submitted to nested PCR. The mutations identified by this method were confirmed by direct sequencing of the PCR amplified product. The highly conserved region of exons 5 to 8 in the p53 gene were screened by an SSCP strategy and the samples with altered electrophoretic mobility were subsequently sequenced.
The statistical analysis of the animal data was performed according to standard techniques for animal carcinogenicity studies (54). The evaluation of the data was divided into two parts: (i) tests on the homogeneity of the P and F1 animals with regard to litter, mortality and weight parameters, and (ii) evaluation of the effects of the treatment on the tumour incidences of the F1 generation. The statistical evaluation of litter size was assessed by the Wilcoxon test. The transgenerational effect of urethane or X-ray irradiation was evaluated by comparison between groups KNi and UNi, KNi and RNi, or KNi and RNAi to determine whether treatment of parental males had an effect on the spontaneous tumour incidence in the offspring. The comparison between KUi and UUi, KUi and RUi, or KUi and RUAi provides information on whether the postnatal exposure to low doses of urethane may promote or modify the occurrence of tumours induced by parental treatment. Comparison between saline- and urethane-treated F1 animals of the same parental group such as KNi and KUi, UNi and UUi, RNi and RUi, or RNAi and RUAi revealed information about the promoting effect of a low dose of urethane. The effect of actual time of application during spermatogenesis on the tumour rates was evaluated by comparing the appropriate values between groups XN 1, XN 3, XN 9 (X = K, U, R, RA). In multiple tests, P-values were adjusted with the stepdown permutation resampling method (55,56).
Statistical procedures were performed using an SAS software package (version 6.09 or 6.12 on DEC Alpha Server 2000 4/233 running Open-VMS 6.2) for all tests.
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Results
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Gonadal X-irradiation significantly decreased the number of weaned offspring per treated male parent in a dose-dependent manner (Table I
). No offspring was born by one paternal mouse, after all three mating time-points, in each of the irradiation groups. Furthermore, the total dose of 2 Gy led to a time-dependent radiation influence on the mating and weaning results. The number of F1 animals in the 3- and 9-week mating time-points was significantly lower than in the other groups. The mean lifetime tabulation demonstrates an almost uniform distribution within the total male or female groups (Table II
).
Paternal urethane treatment led to a significantly increased number of lung tumours in treated P males (Table III
). The Fl lung tumour incidence (bronchiolo-alveolar adenomas and adenocarcinomas) was sex-dependent (higher in males). The occurrence of bronchiolo-alveolar adenocarcinomas was considerably increased in male offspring (RN I, RU I) born to paternals mated 1 week after exposure to 2 Gy X-rays. Correspondingly, the ratios of carcinomas to adenomas were increased (Table IV
).
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Table III. Groups, number of animals and summarized tumour incidences (%) of lung, liver and haematopoietic system
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Lymphomas and histiocytic sarcomas as systemic tumours of the haematopoietic system occurred more often in females (Table III
). In addition, female offspring (RN I, RU I) of the 2 Gy-irradiated males that were mated a week later exhibited a trend towards a higher incidence of tumours of the haematopoietic system than the F1 controls, irrespective of the F1-subtreatment.
Liver tumours (hepatocellular adenomas and adenocarcinomas) were observed mostly in males, where 5362% occurred spontaneously (KP, KN I, III, IX). A significant increase in liver tumours was observed in urethane-treated P males. A relationship was not seen between paternal treatment and the F1 liver tumour incidences in either sex (Table III
). Also, the ratio of carcinomas to adenomas was not affected (Table V
).
Analysis of frozen tissue showed that the incidences of K-ras mutations in F1 mouse lung carcinogenesis increased significantly during tumour progression from hyperplasia (18%) to adenoma (75%) and carcinoma (80%) (53). Urethane treatment increased the incidence of K-ras mutations in codon 61, with CAA
CTA being the most frequent mutation type. Codon 61 K-ras mutations were more frequent in lung tumours of the urethane-promoted progeny (71%) from irradiated parents than from control parents (56%). No p53 mutations in exon 5 to 8 were detected in any of the bronchiolo-alveolar hyperplasias, adenomas or adenocarcinomas (53).
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Discussion
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A significant reduction in the number of litters born and in litter size after paternal irradiation demonstrates effective radiation doses and alteration of spermatogenesis. Oligo- and pathospermia (57) as well as fetal death and resorption (58) are the results of testicular irradiation. The above fertility parameters were not significantly influenced after paternal urethane treatment. Correspondingly, Nomura (22) did not observe increased dominant lethal mutations in ICR mice when urethane (1.52.25 mg/g body wt)-treated paternals were mated after 1, 3 and 9 weeks. The cytotoxic effects of urethane in germ cells, mainly in spermatogonia, were held responsible for slightly reduced litter sizes (59).
The mean lifetime in almost all groups was in the range observed in a pilot pre-study group, i.e. 88 weeks in males, 94 weeks in females (data not shown). The significantly shorter mean lifetime in the progeny control groups (KU I) seems to be incidental. The decreased mean lifetime in the male (RN IX) and female (RN IX, RNA IX) offspring born to X-ray-treated males may be correlated to paternal irradiation (spermatogonia damage), but the animal number per group was too low to draw a final conclusion.
Spontaneous lung tumour rates were in accordance with published (33) and our own pre-study data (data not shown), whereas the liver tumour rates in male mice were higher. The reason for the lower lung tumour rate in the untreated P females (813%) compared with saline-treated F1 females (1619%) is not well understood. The most obvious difference is that in P females a pregnancy and lactation/weaning period took place, which led to a completely different metabolic status. Furthermore, the promoting treatment with urethane resulted in an ~10% lower lung tumour incidence of F1 females compared with F1 males. Similar sex differences were observed in A/J and C57BL/6J mice (60). Possible reasons are the pooling of results without looking for a sex difference or the administration of fixed doses per mouse regardless of body weight (60).
Although statistically not significant, an increased incidence of haematopoietic and lung tumours in offspring born to 2 Gy-irradiated paternals mated 1 week after irradiation underlines, in accordance with Nomura's work (22), a higher sensitivity of post-meiotic germ cells (spermatozoa and spermatids) than of (pre-meiotic) spermatogonia to transgenerational carcinogenic effects. The additional urethane-promoting treatment of F1 progeny born to irradiated males did not result in increased lung tumour rates, in contrast to the results of Nomura (40) and Vorobtsova and Kitaev (23).
A higher percentage of bronchiolo-alveolar adenocarcinomas in male offspring born to irradiated paternals mated 1 week after X-ray treatment indicates that the exposure of post-meiotic germ cell stages may result in an increased risk of malignancy. An analogous increased ratio of malignant to benign tumours was shown by Mohr et al. in descendants of Syrian hamsters exposed prenatally to DEN (61). On the other hand, a systematically increased malignancy towards hepatocellular adenocarcinomas was not observed in any of the offspring groups in our study. Overall F1 liver tumour incidences in both sexes did not seem to be affected by paternal treatment. In contrast, Watanabe et al. reported significantly increased liver tumours in male (B6C3F1) offspring of 50 cGy 252Cf neutron-exposed paternal C3H/HeN mated 2 weeks after irradiation with untreated female C57BL/6N mice (24).
In accordance with literature tabulation (62) female CBA/J mice showed a higher spontaneous tumour rate of the haematopoietic system compared with males. There was a trend towards increased incidence of haematopoietic tissue tumours in the offspring of paternals exposed to X-rays and mated 1 week later, but the increase, while of potential biological relevance, was not statistically significant.
Summarizing the tumour incidences of lung, liver and haematopoietic tissue, there was no uniform tendency in male and female progeny groups. In our study, tumour incidences of lungs, liver and haematopoietic tissue were evaluated together whereas other investigators mostly described tumour rates of a single organ system, e.g. lung (22,23,36,40), liver (24) or the haematopoietic system (63).
Statistically, the tumour evaluation of all three organ systems required an adjustment of the P-values obtained after multiple testing. After running this procedure (stepdown permutation resampling method) there were no statistically significant different tumour incidences in the F1 progeny compared with the respective control groups. Nevertheless, several increased tumour incidences were seen in the 1 week offspring groups of irradiated paternal CBA/J mice; i.e. in our experiment, spermatozoa and late spermatids were the most sensitive cells for transmitting a transgenerational risk. The increased lung tumour rate and multiplicity after paternal urethane treatment reported by Nomura (22,41) in ICR mice could not be confirmed.
The specific codon 61 K-ras mutations in lung tumours of urethane-treated mice are in accordance with the data of You et al. (46). The similar incidence of K-ras mutations in bronchiolo-alveolar adenomas and carcinomas supports the role of these mutations in the early steps of mouse lung carcinogenesis, but not in the progression from adenoma to carcinoma (53). Furthermore, the higher frequency of Codon 61 K-ras mutations in urethane-promoted progeny from irradiated parents than from control parents provides some indication of a possible transgenerational transmission of genomic instability. The absence of p53 mutations in the same lung alterations suggests that p53 mutations may play no role in co-operation with mutations in the K-ras gene nor represent an alternative path of mouse lung carcinogenesis (53).
The relevance of our study to the human situation is related to the widely accepted hypothesis that humans may inherit, through the germ-line, a predisposition to certain cancers and/or a greater susceptibility to environmental carcinogens. Such a predisposition or increased susceptibility is most likely the expression of damage to germ cells that may occur as a consequence of either spontaneous errors in DNA replication and repair or of exposure to a damaging agent. In conclusion, the increased tumour incidences observed in some of the experimental groups following preconceptual exposure of male parent groups to X-rays and urethane may have biological relevance, but are of borderline statistical significance. In spite of the considerable number of animals included in the present study, the numerical size of each experimental group was still insufficient to allow an exhaustive statistical analysis of differences in tumour incidence lower than the 15% originally foreseen.
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Acknowledgments
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The authors wish to thank Mr V.Rehse for his excellent technical assistance and Mrs Gill Teicke for her assistance in text preparation. This research was supported by a grant from the European Union (EV5V-CT92-0222).
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Notes
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4 To whom correspondence should be addressed 
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References
|
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-
Peters,J.M., Preston-Martin,S. and Yu,M.C. (1981) Brain tumours in children and occupational exposure of parents. Science, 213, 235237.[ISI][Medline]
-
Gold,E.B., Diener,M.D. and Szklo,M. (1982) Parental occupations and cancer in children: a case-control study and review of the methodologic issues. J. Occup. Med., 24, 578584.[ISI][Medline]
-
Olshan,A.F., Breslow,N.E., Daling,J.R., Weiss,N.S. and Leviton,A. (1986) Childhood brain tumors and parental occupation in the aerospace industry. J. Natl Cancer Inst., 77, 1719.[ISI][Medline]
-
Draper,G.J. (1989) General overview of studies of multigeneration carcinogenesis in man, particularly in relation to exposure to chemicals. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 275288.Draper,G.J. (1989) General overview of studies of multigeneration carcinogenesis in man, particularly in relation to exposure to chemicals. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 275288.
-
Bunin,G.R., Nass,C.C., Kramer,S. and Meadows,A.T. (1989) Parental occupation and Wilms' tumor. Results of a case-control study. Cancer Res., 49, 725729.[Abstract]
-
Buckley,J.D., Tobison,L.L., Swotinsky,R. et al. (1989) Occupational exposures of parents of children with acute nonlymphocytic leukemia. A report from the childrens cancer study group. Cancer Res., 49, 40304037.[Abstract]
-
Neel,J.V. (1989) The past and future in the study of radiation-induced mutation in the germ-line of mice and humans. Environ. Mol. Mutagen., 14, 5560.[ISI][Medline]
-
Tomatis,L. (1994) Transgeneration carcinogenesis: a review of the experimental and epidemiological evidence. Jpn. J. Cancer Res., 85, 443454.[ISI][Medline]
-
Olshan,A.F. (1995) Lessons learned from epidemiological studies of environmental exposure and genetic disease. Environ. Mol. Mutagen., 25 (suppl. 26), 7480.
-
Yoshimoto,Y. (1990) Cancer risk among children of atomic bomb survivors. JAMA, 264, 596690.[Abstract]
-
Janerich,D.T., Hayden,C.L., Thompson,D.W., Selenkas,S.L. and Mettlin,C. (1989) Epidemiologic evidence of perinatal influence in the etiology of adult cancers. J. Clin. Epidemiol., 42, 151157.[ISI][Medline]
-
Lumey,L.H. (1992) Decreased birthweights in infants after maternal in utero exposure to the Dutch famine of 19441945. Ped. Perinat. Epidemiol., 6, 240243.[Medline]
-
Dubrova,Y.E., Nesterov,V.N., Krouchinsky,N.G., Ostapenko,V.A., Neumann,R., Neil,D.L. and Jeffreys,A.L. (1996) Human minisatellite mutation rate after the Chernobyl accident. Nature, 380, 683686.[ISI][Medline]
-
Baker,R.J., Van Den Bussche,R.A., Wright,A.J., Wiggins,L.E., Hamilton,M.J., Reat,E.P.P., Smith,M.H., Lomakin,M.D. and Chesser,R.K. (1996) High levels of genetic change in rodents of Chernobyl. Nature, 380, 707708.[ISI][Medline]
-
Gardner,M.J., Snee,M.P., Hall,A.J., Powell,C.A., Downes,S. and Terrell,J.D. (1990) Results of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria. Br. Med. J., 300, 423429.[ISI][Medline]
-
Gardner,M.J., Hall,A.J., Snee,M.P., Downes,S., Powell,C.A. and Terrell,J.D. (1990) Methods and basic data of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria. Br. Med. J., 300, 429434.[ISI][Medline]
-
Morris,J.A., Edwards,J.M. and Buckler,J. (1990) Retinoblastoma in grandchildren of workers at Sellafield nuclear plant. Br. Med. J., 301, 1257.[ISI][Medline]
-
Parker,L., Craft,A.W., Smith,J., Dickinson,H., Wakeford,R., Binks,K., McElvenny,D., Scott,L. and Slovak,A. (1993) Geographical distribution of preconceptional radiation doses to fathers employed at the Sellafield nuclear installation, West Cumbria. Br. Med. J., 307, 966971.[ISI][Medline]
-
Doll,R., Evans,H.J. and Darby,S.C. (1994) Paternal exposure not to blame. Nature, 367, 678680.[ISI][Medline]
-
Draper,G.J., Little,M.P., Sorahan,T. et al. (1997) Cancer in the offspring of radiation workers: a record linkage study. Br. Med. J., 315, 11811188.[Abstract/Free Full Text]
-
McLaughlin,J.R., King,W.D., Anderson,T.W., Clarke,E.A. and Ashmore,J.P. (1993) Paternal radiation exposure and leukemia in offspring: the Ontario case-control study. Br. Med. J., 307, 959966.[ISI][Medline]
-
Nomura,T. (1982) Parental exposure to X-rays and chemicals induces heritable tumors and anomalies in mice. Nature, 296, 575577.[ISI][Medline]
-
Vorobtsova,I.E. and Kitaev,E.M. (1988) Urethane-induced lung adenomas in the first-generation progeny of irradiated male mice. Carcinogenesis, 9, 19311934.[Abstract]
-
Watanabe,H., Takahashi,T., Lee,J.Y. et al. (1996) Influence of paternal 252Cf neutron exposure on abnormal sperm, embryonal lethality and liver tumorigenesis in the F1 offspring of mice. Jpn. J. Cancer Res., 87, 5157.[ISI][Medline]
-
Tomatis,L. and Goodall,C.M. (1969) The occurrence of tumors in F1, F2 and F3 descendants of pregnant mice injected with 7,12-dimethylbenz[a]anthracene. Int. J. Cancer, 4, 219225.[ISI][Medline]
-
Tomatis,L., Cabral,J.R.P., Likhachev,A.J. and Ponomarkov,V. (1981) Increased cancer incidence in the progeny of male rats exposed to ethylnitrosourea before mating. Int. J. Cancer, 28, 475478.[ISI][Medline]
-
Nomura,T. (1975) Transmission of tumors and malformations to the next generation of mice subsequent to urethane treatment. Cancer Res., 35, 264266.[ISI][Medline]
-
Walker,B.E. (1984) Tumors of female offspring of mice exposed prenatally to diethylstilbestrol. J. Natl Cancer Inst., 73, 133140.[ISI][Medline]
-
Turusov,V., Nikonova,T.V. and Parfenov,Yu.D. (1990) Increased multiplicity of lung adenomas in five generations of mice treated with benzo[a]pyrene when pregnant. Cancer Lett., 55, 227231.[ISI][Medline]
-
Tomatis,L. (1989) Overview of perinatal and multigeneration carcinogenesis. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 115.Tomatis,L. (1989) Overview of perinatal and multigeneration carcinogenesis. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 115.
-
Napalkov,N., Lichaev,A., Anisimov,V., Loktionov,A., Zabezhinski,M., Ovsyannikov,A., Wahrendorf,J., Becher,H. and Tomatis,L. (1987) Promotion of skin tumours by TPA in the progeny of mice exposed prenatally to DMBA. Carcinogenesis, 8, 381385.[Abstract]
-
Yamasaki,H., Loktionov,A. and Tomatis,L. (1992) Perinatal and multigeneration effect of carcinogens: possible contribution to determination of cancer susceptibility. Environ. Health Perspect., 98, 3943.[ISI][Medline]
-
Shimkin,M.B. and Stoner,G.D. (1975) Lung tumors in mice: applications to carcinogenesis bioassay. Adv. Cancer Res., 22, 158.[Medline]
-
Lyon,M.F. and Renshaw,R. (1988) Induction of congenital malformations in mice by parental irradiation: transmission to later generations. Mutat. Res., 198, 277283.[ISI][Medline]
-
Nomura,T. (1984) Induction of persistent hypersensitivity to lung tumorigenesis by an in utero X-radiation in mice. Environ. Mutagen., 6, 3340.[ISI][Medline]
-
Cattanach,B.M., Patrick,G., Papworth,D., Goodhead,D.T., Hacker,T., Cobb,L. and Whitehill,E. (1995) Investigation of lung tumor induction in BALB/c mice following paternal X-irradiation. Int. J. Radiat. Biol., 67, 607615.[ISI][Medline]
-
Mirvish,S.S. (1968) The carcinogenic action and metabolism of urethan an N-hydroxy-urethan. Adv. Cancer Res., 11, 143.[Medline]
-
IARC (1974) Some Anti-thyroid and Related Substances, Nitrofurans and Industrial Chemicals. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, vol. 7. IARC, Lyon, pp. 111140.
-
Salmon,A.G., Painter,P., Dunn,A.J., Wu-Williams,A., Monserrat,L. and Zeise,L. (1991) Carcinogenic effects. In Salmon,A.G. and Zeise,L. (eds) Risks of Carcinogenesis from Urethane Exposure. CRC Press, Boca Raton, FL, pp. 4877.Salmon,A.G., Painter,P., Dunn,A.J., Wu-Williams,A., Monserrat,L. and Zeise,L. (1991) Carcinogenic effects. In Salmon,A.G. and Zeise,L. (eds) Risks of Carcinogenesis from Urethane Exposure. CRC Press, Boca Raton, FL, pp. 4877.
-
Nomura,T. (1983) X-ray induced germ-line mutation leading to tumors; its manifestation in mice given urethane postnatally. Mutat. Res., 11, 5965.
-
Nomura,T. (1989) Role of radiation-induced mutations in multigeneration carcinogenesis. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 375387.Nomura,T. (1989) Role of radiation-induced mutations in multigeneration carcinogenesis. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 375387.
-
Vorobtsova,I.E. (1989) Increased cancer risk as a genetic effect of ionizing radiation. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 389401.Vorobtsova,I.E. (1989) Increased cancer risk as a genetic effect of ionizing radiation. In Napalkov,N.P., Rice,J.M., Tomatis,L. and Yamasaki,H. (eds) Perinatal and Multigeneration Carcinogenesis. IARC Scientific Publications no. 96, IARC, Lyon, pp. 389401.
-
Tomatis,L., Narod,S. and Yamasaki,H. (1992) Transgeneration transmission of carcinogenic risk. Carcinogenesis, 13, 145151.[ISI][Medline]
-
Balmain,A. and Brown,K. (1988) Oncogene activation in chemical carcinogenesis. Adv. Cancer Res., 51, 147182.[ISI][Medline]
-
Wiseman,R.W., Stewart,B.C., Grenier,D., Miller,E.C. and Miller,J.A. (1987) Characterization of the c-Ha-ras protooncogene mutations in chemically induced hepatomas of the male B6C3F1 mouse. Proc. Am. Assoc. Cancer Res., 28, 147.
-
You,M., Candrain,U., Maronpot,R.R., Stoner,G.D. and Anderson,M.W. (1989) Activation of the K-ras protooncogene in spontaneously occurring and chemically induced lung tumors of the strain A mouse. Proc. Natl Acad. Sci. USA, 86, 30703074.[Abstract]
-
Zhuang,S.M., Cochran,S., Goodrow,T., Wiseman,R.W. and Söderkvist,P. (1997) Genetic alterations of p53 and ras genes in 1,3-butadiene- and 2',3'-dideoxycytidine-induced lymphomas. Cancer Res., 57, 27102714.[Abstract]
-
Levine,A.J., Momand,J. and Finlay,C.A. (1991) The p53 tumour suppressor gene. Nature, 351, 453456.[ISI][Medline]
-
Hollstein,M., Sridanski,D., Vogelstein,B. and Harris,C.C. (1991) p53 mutations in human cancers. Science, 253, 4953.[ISI][Medline]
-
Malkin,D., Li,F.P., Strong,L.C. et al. (1990) Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas and other neoplasms. Science, 250, 12331238.[ISI][Medline]
-
Srivastava,S., Zou,Z.Q., Pirollo,K., Blattner,W. and Chang,E.H. (1990) Germ-line transmission of a mutated p53 gene in a cancer-prone family with Li-Fraumeni syndrome. Nature, 348, 747749.[ISI][Medline]
-
Turusov,V.S. and Mohr,U. (eds) (1994) Pathology of Tumours in Laboratory Animals, Vol. 2, Tumours of the Mouse, No. 111. IARC, Lyon.Turusov,V.S. and Mohr,U. (eds) (1994) Pathology of Tumours in Laboratory Animals, Vol. 2, Tumours of the Mouse, No. 111. IARC, Lyon.
-
Cazorla,M., Hernández,L., Fernández,P.L. et al. (1997) K-ras gene mutations and absence of p53 gene mutations of spontaneous and urethane-induced early lung lesions in CBA/J mice. Mol. Carcinogen., 21, 252260.
-
Gart,J.J., Krewski,D., Lee,P.N., Tarone,R.E. and Wahrendorf,J. (1986) The Design and Analysis of Long-term Animal Experiments. IARC Scientific Publications no. 79, IARC, Lyon.
-
Hochberg,Y. and Tamhane,A.C. (1987) Multiple Comparison Procedures. John Wiley & Sons, New York, NY.
-
Westfall,P.H. and Young,S.S. (1993) Resampling-based Multiple Testing: Examples and Methods for P-Value Adjustment. John Wiley & Sons, New York, NY.
-
Meistrich,M.L. (1986) Critical components of testicular function and sensitivity to disruption. Biol. Reprod., 34, 1728.[Abstract]
-
Wachsmann,F. (1982) Einfluß der zeit zwischen bestrahlung und befruchtung auf die F-1-generation der maus. In Kriegel,H., Schmahl,W., Kistner,G. and Stieve,F.E. (eds) Entwicklungsstörungen nach Pränataler Bestrahlung [Developmental Effects of Prenatal Irradiation]. G. Fischer Verlag, Stuttgart, pp. 7984.
-
Russell,L.B., Hunsicker,P.R., Oakberg,E.F., Cummings,C.G. and Schmoyer,R.L. (1987) Tests for urethane induction of germ-cell mutations and germ-cell killing in the mouse. Mutat. Res., 188, 335342.[ISI][Medline]
-
Festing,M.F.W., Yang,A. and Malkinson,A.M. (1994) At least four genes and sex are associated with susceptibility to urethane-induced pulmonary adenomas in mice. Genet. Res., 64, 99106.[ISI][Medline]
-
Mohr,U., Emura,M., Kamino,K., Steinmann,J., Kohler,M., Morawietz,G., Dasenbrock,C. and Tomatis,L. (1995) Increased risk of cancer in the descendants of Syrian hamsters exposed to DEN. Int. J. Cancer, 63, 8691.[ISI][Medline]
-
Steinborn,P. (1989) Stammesdifferenzen des mittleren Lebensalters und der spontanen und induzierten tumorhäufigkeit bei mäuseinzuchstämmen (Literaturübersicht bis 1987). Inaug. Diss., Tierärztliche Hochschule Hannover.
-
Nomura,T. (1991) Paternal exposure to radiation and offspring cancer in mice: reanalysis and new evidences. J. Radiat. Res., 2 (suppl.), 6472.
Received June 23, 1998;
revised October 12, 1998;
accepted October 21, 1998.