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Objectives: To extend follow-up of cause-specific mortality in workers at seven beryllium processing plants and to estimate associations between mortality risk and beryllium exposure., Methods: 9199 workers were followed for mortality from 1940 through 2005. Standardised mortality ratios (SMRs) were estimated based on US population comparisons for lung, nervous system and urinary tract cancers, chronic obstructive pulmonary disease (COPD), chronic kidney disease, and categories containing chronic beryllium disease (CBD) and cor pulmonale. Associations with maximum and cumulative exposure were calculated for a subset of the workers., Results: Overall mortality in the cohort compared with the US population was elevated for lung cancer (SMR 1.17; 95% CI 1.08 to 1.28), COPD (SMR 1.23; 95% CI 1.13 to 1.32), and the categories containing CBD (SMR 7.80; 95% CI 6.26 to 9.60) and cor pulmonale (SMR 1.17; 95% CI 1.08 to 1.26). Mortality rates for most diseases of interest increased with time-since-hire. For the category including CBD, rates were substantially elevated compared to the US population across all exposure groups. Workers whose maximum beryllium exposure was ≥ 10 μg/m(3) had higher rates of lung cancer, urinary tract cancer, COPD and the category containing cor pulmonale than workers with lower exposure. Significant positive trends with cumulative exposure were observed for nervous system cancers (p = 0.0006) and, when short-term workers were excluded, lung cancer (p = 0.01), urinary tract cancer (p = 0.003) and COPD (p < 0.0001)., Conclusion: These findings reaffirm that lung cancer and CBD, and suggest that COPD and nervous system and urinary tract cancers, are related to beryllium exposure. Cigarette smoking and exposure to other lung carcinogens are unlikely to explain these elevations.

The Long-Evans Cinnamon (LEC) rat, an animal model of Wilson's disease, is resistant to a variety of chemical carcinogenesis except liver and colon. In the present study, N-ethyl-N-nitrosourea (ENU)-induced transplacental carcinogenesis was examined in male and female LEC, Long-Evans Agouti (LEA), a sibling line of the LEC rat, and F344 rats (n=21). ENU was administered to pregnant rats as a single s.c. injection at a dose of 60 mg/kg body weight on the 17th day after conception. Cerebral/spinal gliomas and trigeminal/spinal nerve schwannomas developed in both LEA and F344 rats at 30 weeks of age, but no nervous system tumors developed in LEC rats, the difference being statistically significant. Lung adenomas also developed in LEA and F344 rats, but not in LEC rats. Semiquantitative RT-PCR demonstrated that metallothionein (MT)1a, MT2 and O(6)-methylguanine-DNA methyltransferase (MGMT) mRNA levels in the liver of LEC rats were higher than those in F344 and LEA rats. In addition, Western blot analysis showed that MT (MT1 plus MT2) in the liver of LEC rats was also higher than that in other strains. Present results suggest that high levels of MT and/or MGMT contribute to the resistance to nitrosamine-induced carcinogenesis in LEC rats.

Background: The mortality experience of pesticide-exposed workers across the US has not been thoroughly studied., Methods: Cox regression mortality analyses adjusted for the complex sample survey design were performed on mortality-linked 1986-1994 National Health Interview Survey (NHIS) data., Results: Nine thousand four hundred seventy-one farmers and pesticide applicators with 571 deaths were compared to 438,228 other US workers with 11,992 deaths. Age-adjusted risk of accidental death, as well as cancers of the nervous and lymphatic/hematopoietic systems, was significantly elevated in male and female pesticide-exposed workers; breast, prostate, and testicular cancer mortality risks were not elevated., Conclusions: Compared to all other workers, farmers and pesticide applicators were at greater risk of accidental mortality. These pesticide-exposed workers were not at an increased risk of cancers possibly associated with exposure to estrogen analogue compounds, but were at an increased risk of hematopoietic and nervous system cancers. NHIS mortality follow-up represents an important occupational health surveillance instrument., (Copyright 2003 Wiley-Liss, Inc.)

The anticarcinogenic effects and mechanisms of the biotechnological drugs of Panax ginseng C.A. Meyer cultivated in Russia, bioginseng, panaxel and panaxel- 5, were studied. Bioginseng was produced from a tissue culture of ginseng root cultured on standard medium, whereas panaxel and panaxel-5 were produced from ginseng tissue root cultures using standard mediums enriched with 2-carboxyethylgermanium sesquioxide and 1-hydroxygermatran-monohydrate respectively. All three ginseng drugs inhibited the development of mammary tumors induced by intramammary injections of N-methyl-N-nitrosourea (MNU) in rats, the development of the brain and spinal cord tumors induced by transplacental administration of N-ethyl-N-nitrosourea (ENU) in rats, and the development of uterine, cervical and vaginal tumors induced by intravaginal applications of 7,12-dimethylbenz(a)anthracene (DMBA) in mice. The ginseng drugs induced the cytotoxic activity of macrophages in mice, enhanced T-lymphocyte rosette formation in guinea pigs exposed to cyclophosphamide, and stimulated the production of thyroid hormones in rats. These mechanisms may contribute to the anticarcinogenic action of the ginseng drugs. The organic germanium compounds present in panaxel and panaxel-5 did not potentiate the anticarcinogenic or immuno- stimulatory effects as much as biogeinseng. Preliminary clinical trials with panaxel and bioginseng were carried out in patients with precancerous lesions of the esophagus and endometrium. Panaxel was found to have a strong therapeutic effect in patients suffering from chronic erosive esophagitis. Bioginseng induced the regression of adenomatous-cystic hyperplasia of the endometrium in some patients. Thus, we conclude that the drugs of ginseng appear to hold considerable promise for future cancer chemoprevention.

Interspecific hybrid crosses between members of the fish genus Xiphophorus have been used for over 70 years to study the genetic aspects of melanoma formation. In the well-established "Gordon-Kosswig" cross, the platyfish X. maculatus is outcrossed to the swordtail X. helleri, and the resulting backcross segregants spontaneously develop melanoma. We recently produced a distinct cross between X. maculatus and another platyfish species, X. couchianus. X. maculatus strain Jp 163 A is homozygous for several X-linked pigment pattern genes, including the Spotted dorsal (Sd), Dorsal red (Dr), and Anal fin spot (Af). Af is a sex-limited trait, coding exclusively for melanophores distributed on the modified anal fin or "gonopodium" in the adult male fish. Within F1 and BC1 hybrids (to X. couchianus), the Sd pigment pattern is phenotypically suppressed, whereas Dr and Af are enhanced. We exposed BC1 hybrids to the direct-acting carcinogen N-methyl-N-nitrosourea (MNU). Treatment led to the development of schwannomas, fibrosarcomas, and retinoblastomas. In addition, numerous MNU-treated males that inherited Af developed a pronounced melanotic phenotype, with melanin-containing cells oftentimes totally covering the gonopodium and extending further to grow within the ventral regions of the fish. Genetic linkage analysis of the BC1 hybrids revealed a significant (p < 0.01) association between CDKN2X genotype and the phenotypic degree of melanization. Such an association is consistent with a locus within linkage group V playing a role in the development of melanosis and delineates three genetic preconditions and a carcinogenic scheme resulting in melanosis of the ventral regions of hybrid fish. The overall study further alludes to the potential of using Xiphophorus fish to study carcinogenic mechanisms for tumors other than melanoma (schwannoma, fibrosarcoma, and retinoblastoma) and should enable extensive pathologic and molecular genetic studies of derived neoplastic abnormalities.

The objective of the study described here was to test the hypothesis that paternal occupational exposure near conception increases the risk of cancer in the offspring. We conducted a cohort study based on a population of 235,635 children born shortly after two different censuses in Sweden. The children were followed from birth to 14 years, and cases of cancer were identified in the Swedish Cancer Registry. Occupational hygienists assessed the probability of exposure to different agents in each combination of the father's industry and occupation as reported in the censuses. We also analyzed individual job titles. We compared the cancer incidence among children of exposed fathers to that among children of unexposed fathers using Cox proportional hazards modeling. The main findings were an increased risk of nervous system tumors related to paternal occupational exposure to pesticides [relative risk (RR) = 2.36; 95% confidence interval (CI), 1.27-4.39] and work as a painter (RR = 3.65; 95% CI, 1.71-7.80), and an increased risk of leukemia related to wood work by fathers (RR = 2.18; 95% CI, 1.26-3.78). We found no associations between childhood leukemia and paternal exposure to pesticides or paint. Our results support previous findings of an increased risk of childhood brain tumors and leukemia associated with certain paternal occupational exposures. Some findings in previous studies were not confirmed in this study.

Objectives: The industrialization process and nervous system cancer (NSC) mortality in a urban region of Brazil., Method: From registries of the State System of Data Analysis Foundation (SEADE), 103 males deaths by NSC (ICD-9) in Baixada Santista (BS), from 1980 to 1993 were selected. Mortality ratios were calculated comparing the standardized mortality rate for ages over 10 years old (G1) and for the age group from 35 to 64 years old, in the industrialized and non-industrialized areas in three periods: 1980-1993, 1980-86, 1987-93., Results: A statiscally significant high mortality was observed in the industrialized area, for ages over 10 in all periods and only from 1980 to 1993 for ages from 34 to 64. The highest mortality ratio occurred from 1980-86 for ages over 10 - 4.12 (CI 1.79-9.42)., Conclusion: High mortality was probably related to the environmental and occupational exposure to many organic and inorganic chemical substances, considered carcinogenics, such as aliphatic and aromatic hydrocarbons, organochlorinated, formaldehyde, nitrogenated compounds and heavy metals, found in the port and industrial complex. We discuss the importance of case-control studies in characterizing the association of these and other risk factors in the determination of NSC.

In the absence of adequate data on humans, it is biologically plausible and prudent to regard agents and mixtures for which there is sufficient evidence of carcinogenicity in experimental animals, usually rats and mice, as if they presented a carcinogenic risk to humans. Prediction of cancer sites in humans from bioassay data in rodents is much less certain, however, regardless of organ or tissue. For tumors of the nervous system, there is practically no basis for judging the validity of such predictions, as only ionizing radiation is known to cause tumors of the central nervous system (CNS) in humans. Brain tumors are relatively uncommon findings in bioassays and are rare in untreated rodents, even in rats, which appear to be the most susceptible species. However, CNS tumors have been readily induced in rodents by systemic exposures to some chemicals, notably N-nitrosoalkylureas and other alkylating agents and certain alkyl hydrazine derivatives. CNS tumors in rodents have played a significant role in carcinogenic hazard evaluations of several other chemicals, including acrylonitrile, ethylene oxide, and acrylamide, and have been implicated as part of the tumor spectrum induced by vinyl chloride and certain inorganic lead compounds. In some of these evaluations, it is not certain that all tumors diagnosed as primary brain tumors were correctly identified. Diagnostic difficulties have been presented by undifferentiated small-cell tumors that may invade the brain, including carcinomas of the nasal cavity and undifferentiated schwannomas arising in cranial nerve ganglia, and by the difficulty of reliably distinguishing between focal reactive gliosis and early glial neoplasms. The most striking experimental finding regarding the induction by chemicals of tumors of the nervous system is the dramatically greater susceptibility of the fetal and neonatal nervous system to some carcinogens, as compared with the susceptibility of the nervous system in adults of the same species.

Rats developed mixed gliomas, oligodendrogliomas, and a few astrocytomas in response to transplacental ethylnitrosourea. The neoplastic cell composition of mixed gliomas must be defined; this study required a 20-80% admixture of neoplastic astrocytes and oligodendroglia for the diagnosis of mixed glioma. A battery of immunoantibodies, including Leu-7, S-100, and vimentin, were helpful in classifying rat gliomas, and the histologic features of each tumor type are described. Other brain tumor characteristics that may decide the outcome of carcinogenicity studies include incidence, multiplicity, latency, fatality, size, and malignancy. The size of tumors was determined by measuring their 3-dimensional volumes. Brain tumor volume was found to be highly correlated with malignancy and fatality. Systematic evaluation of the malignancy of brain tumors is an important but often overlooked adjunct method of measuring the effectiveness of a carcinogen. A system to estimate malignancy, one that grades 9 tumor characteristics and weights, each according to clinical outcome, was developed. It was found that mixed gliomas grew larger, had a shorter latency, and were significantly more malignant than were other gliomas.

The present study investigates nitrosourea-induced rat (Rattus norvegicus) glioma cell lines for the functional status of the p16/Cdkn2a/Ink4a gene, which encodes the p16 cdk4 inhibitor and the alternative reading frame protein, p19ARF. We detected homozygous deletions of the p16/Cdkn2a/Ink4a gene locus in 4 of 5 glioma cell lines (C6, F98, RG2, and RGL.3), but not in the 9L gliosarcoma cell line or in a rat primary fibroblast cell line. RT-PCR demonstrated expression of the p16 and p19ARF mRNAs only in 9L cells and in rat fibroblasts. Comparative genomic in situ hybridization showed that the copy number of rat chromosome RNO5 was not altered in any of the glioma cell lines investigated, indicating that the deletions result from a discrete loss in the region of the p16/Cdkn2a/Ink4a locus. This is the first report of p16/Cdkn2a/Ink4a deletions present in nitrosourea-induced rat glioma cell lines. Since this genetic alteration is also commonly observed in human malignant glial tumors, our results validate the use of chemically induced rat glioma cell lines as an experimental model in the development of gene therapy strategies., (Copyright 2000 S. Karger AG, Basel.)

As part of investigations on ethylnitrosourea (EtNU)-induced neuro-oncogenesis in the rat, we have produced monoclonal antibodies (Mabs) specific for neural cell surface antigens (NCAs) by immunization with cells of the clonal tumorigenic neural rat cell line BT4Ca. Mabs designated as anti-NCA (alpha NCA1, alpha NCA2, alpha NCA3, alpha NCA4, and alpha NCA5) recognize proteins of 25 kDa and 23 kDa, as shown by immunoprecipitation and Western blot. The predominant 25-kDa protein was purified from BT4Ca cells by immunoaffinity chromatography with immobilized Mab alpha NCA1 and identified by N-terminal sequencing as the rat homologue of the CD9 antigen. Identification of proline as N-terminal amino acid of the purified protein suggests post-translational modification of CD9 in the rat central nervous system. The NCA/CD9 protein was localized in distinct regions of fetal and adult rat brain by immunofluorescence staining of frozen sections. Flow cytometric analyses of isolated fetal rat brain cells (FBC) showed that the proportion and number of NCA/CD9-expressing cells increased during prenatal development. Immunoreactivity of approximately 40% of brain cells isolated 13 days post conception (p.c.) indicated that NCA/CD9 is expressed by neuronal precursors at this stage of development. In primary cultures of rat FBC isolated 18 days p.c., the NCA/CD9 antigen was expressed by all premature and mature astrocytes, oligodendrocytes, ependymal cells, and microglial cells, but not by E-N-CAM-expressing neuronal progenitor cells and neurons. Furthermore, eight out of ten EtNU-induced malignant neural rat cell lines as well as EtNU-induced tumors of the central and peripheral nervous system exhibited intermediate or strong immunoreactivity with Mab alpha NCA1. Expression of the NCA/CD9 protein is, therefore, characteristic of both normal glial precursor cells and their malignant counterparts in the rat.

Syrian golden hamsters have a very short period (15 days) of gestation. The implantation of the blastocyst occurs on day 5, embryogenesis proceeds very rapidly thereafter and neural tube closure is completed by day 9. In the present study the effects of two different doses of N-nitrosoethylurea (NEU) administered at various stages of gestation were quantitatively evaluated in Syrian golden hamsters. NEU at either 0.2 or 0.5 mmol/kg was administered transplacentally as a single i.p. injection to pregnant hamsters on gestation days 7, 8, 9, 10, 11, 12, 13, or 14. The incidence, latency period and multiplicity of tumors varied with the dose of NEU and the stage of development at the time of NEU administration. Although tumors of the peripheral nervous system predominated, a variety of other tumors, including melanomas and visceral tumors of epithelial and mesenchymal origin, were also observed in hamster offspring exposed transplacentally to NEU. Sensitivity to transplacental carcinogenesis was maximal during late gestation and very low before day 9.

Ethylnitrosourea (ENU) given transplacentally to rats induces schwannomas of the cranial, spinal and peripheral nerves with a high frequency of mutation in the neu proto-oncogene. To establish the requirement for such mutation in tumorigenesis of Schwann cells, spontaneous schwannomas from BD-VI strain rats were evaluated for transforming mutations in the transmembrane domain of the encoded protein for the neu proto-oncogene. Whereas all five schwannomas induced by ENU showed T/A transversions in codon 2012 of neu oncogene upon analysis by selective oligonucleotide hybridization and dideoxy sequencing of polymerize chain reaction amplified products from paraffin sections, only one of nine spontaneous schwannomas from untreated rats exhibited the same mutation. Examination of tumours for mutation in codon 12 of Ki-ras proto-oncogene revealed normal alleles. Our conclusions based on these data are that the high frequency of mutations in neu in ENU-induced tumours appears to be attributable to the carcinogen or to the period of development at which exposure occurred, and that transforming mutations of the transmembrane domain of neu, are not required for tumorigenesis of the Schwann cell.

The model of experimental tumors of the nervous system has greatly contributed to our understanding of growth and management of intracranial tumors, but has been somewhat neglected in the last years, because a wealth of new data concerning oncogenic action came from viral oncogenesis. These new issues led to a much better insight into human tumor induction and promotion. Yet one example of the impact of oncogenic transformation stems from the "neurooncogenic" model: the discovery of the neu oncogene and its product as a putative differentiation receptor in the cell membrane of experimental Schwann cell derived tumors. In the light of this unique finding the history of the "neurooncogenic" model and the morphological and "clinical" result of tumors produced within the model are reviewed. There is a large open field for future investigation both in basic and applied science.

Mortality from cancer among workers exposed to ethylene oxide (EtO) has been studied in 10 distinct cohorts that include about 29,800 workers and 2540 deaths. This paper presents a review and meta-analysis of these studies, primarily for leukaemia, non-Hodgkin's lymphoma, stomach cancer, pancreatic cancer, and cancer of the brain and nervous system. The magnitude and consistency of the standardised mortality ratios (SMRs) were evaluated for the individual and combined studies, as well as trends by intensity or frequency of exposure, by duration of exposure, and by latency (time since first exposure). Exposures to other workplace chemicals were examined as possible confounder variables. Three small studies by Hogstedt initially suggested an association between EtO and leukaemia, but in seven subsequent studies the SMRs for leukaemia have been much lower. For the combined studies the SMR = 1.06 (95% confidence interval (95% CI) 0.73-1.48). There was a slight suggestion of a trend by duration of exposure (p = 0.19) and a suggested increase with longer latency (p = 0.07), but there was no overall trend in risk of leukaemia by intensity or frequency of exposure; nor did a cumulative exposure analysis in the largest study indicate a quantitative association. There was also an indication that in two studies with increased risks the workers had been exposed to other potential carcinogens. For non-Hodgkin's lymphoma there was a suggestive risk overall (SMR = 1.35, 95% CI 0.93-1.90). Breakdowns by exposure intensity or frequency, exposure duration, or latency did not indicate an association, but a positive trend by cumulative exposure (p = 0.05) was seen in the largest study. There was a suggested increase in the overall SMR for stomach cancer (SMR = 1.28, 95% CI 0.98-1.65 (CI 0.73-2.26 when heterogeneity among the risk estimates was taken into account)), but analyses by intensity or duration of exposure or cumulative exposure did not support a causal association for stomach cancer. The overall SMRs and exposure-response analyses did not indicate a risk from EtO for pancreatic cancer (SMR = 0.98), brain and nervous system cancer (SMR = 0.89), or total cancer (SMR = 0.94). Although the current data do not provide consistent and convincing evidence that EtO causes leukaemia or non-Hodgkin's lymphoma, the issues are not resolved and await further studies of exposed populations.

The anticarcinogenic effects of the nonsteroidal antiinflammatory drugs ortophen and indomethacin on carcinogenesis of the nervous and renal systems were studied. Glial tumors of the brain and spinal cord, neurinomas of peripheral nerves and renal mesenchymal tumors were induced in rats through a single transplacental administration of N-ethyl-N-nitrosourea, 75 mg/kg body weight. Ortophen and indomethacin each used in a dose of 20 mg/litre of drinking water in the period of postnatal life were effective in inhibiting the growth of brain and spinal cord tumors, showed a statistically insignificant tendency to suppress the growth of peripheral nervous tumors, but failed to affect the growth of renal tumors.

Despite the fact that the teratogenic effects of phenytoin have been suggested in several case reports, the evidence for a possible oncogenic potential of phenytoin has not been widely recognized. Recently, neuroblastoma as well as other neuroectodermal and non-ectodermal tumors has been seen in several children exposed to phenytoin prenatally. Previous cases have been almost uniformly associated with the features of "fetal hydantoin syndrome" and none have been developmentally normal. We report a developmentally-normal boy of 21/2 years with an abdominal neuroblastoma whose mother had been on phenytoin (as well as carbamazepine) throughout gestation. We review the various neoplasms which have been reported in the offspring of mothers receiving phenytoin.

Anticarcinogenic effects of the fumaric acid was studied in two rat models of carcinogenesis. Tumors of the esophagus, forestomach, tongue and throat were induced by peroral instillation of 35 mg/kg body weight N-methyl-N-benzylnitrosamine, and neurogenic and renal ones--by transplacental injection of 75 mg/kg body weight N-ethyl-N-nitrosourea. The fumaric acid given in drinking water in the dose of 1 g/l at the postinitiation stage of the carcinogenesis was shown to inhibit the development of esophageal papilloma, brain glioma and mesenchymal tumors of the kidney.

The anticarcinogenic properties of epsilon-aminocaproic acid were studied in two rat models of carcinogenesis. Esophageal tumors were induced by oral instillations of a total dose of 54 mg/kg body weight N-methyl-N-benzylnitrosamine whereas tumors of the nervous system and kidney-by transplacental injection of 75 mg/kg body weight N-ethyl-N-nitrosourea. epsilon-Aminocaproic acid given at a concentration of 1 milligram drinking water at the post-initiation stage of the carcinogenesis was shown to inhibit the induction of cancer and papilloma of the esophagus, brain glioma, peripheral nerve neurinoma and mesenchymal tumors of the kidney.

The study was concerned with the inhibitory effect of officinal preparations of phytoadaptogenic drugs such as bioginseng and Eleutherococcus senticosus and Rhaponticum carthamoides root extracts on the carcinogenesis induced by transplacental administration of N-nitrosoethylurea. The phytodrugs were given orally over a year. The administration of the drugs was followed by longer survival of the rats and lower occurrence and/or multiplicity of tumors (mainly those of the central nervous system). The drugs were placed in the order of decreasing anticarcinogenic activity as follows: bioginseng, Rhaponticum carthamoides extract and Eleutherococcus senticosus extract.

We studied the influence of the vitamins retinol acetate, alpha-tocopherol acetate and thiamine chloride; the antioxidant sodium selenite and an inhibitor of polyamine biosynthesis, alpha-difluoromethylornithine, on the offspring of transplacental carcinogenesis by ethylnitrosourea in rats. Ethylnitrosourea was given to pregnant rats as a single i.v. injection, at a dose of 75 mg/kg body wt. or 5.5 mg/kg body wt., on the 21st day after conception. Retinol, tocopherol or thiamine was added to the diet, and selenite and alpha-difluoromethylornithine to drinking water of the offspring throughout their postnatal life at moderate doses. In control groups, ethylnitrosourea induced tumors of brain, spinal cord, peripheral nervous system and kidneys in the offspring. alpha-Difluoromethylornithine exerted a slight inhibitory effect; this agent decreased the total tumor multiplicity and the multiplicity of peripheral nervous system tumors and also prolonged survival time. Retinol, tocopherol, thiamine and selenite did not influence the development of the transplacentally-induced tumors.

Neuroendocrine lung cancers can be induced in hamsters within 8-12 weeks by combined exposure to N-nitrosodiethylamine (DEN) and hyperoxia. The expression of the c-Ki-ras gene in this lung cancer model was studied using polymerase chain reaction analysis of mRNA (RNA/PCR). We used four different groups of hamsters, exposed for 6 weeks to DEN with hyperoxia (60% oxygen), DEN, hyperoxia, or ambient air, respectively. Total RNA was isolated from lung tissues and cDNA made prior to PCR amplification. A 234-bp product was amplified from c-Ki-ras cDNA and quantitated using scanning laser densitometry. The data obtained were normalized to the expression of the house keeping gene B-actin. The c-Ki-ras products were present after amplification of all hamster lung RNA samples. The hamster lungs exposed to DEN with hyperoxia displayed higher c-Ki-ras protooncogene expression than hamsters exposed to DEN, hyperoxia, or ambient air alone. Since the animals studied were sacrificed at 6 weeks, prior to the appearance of tumors, we conclude that this increased expression may indicate a role for c-Ki-ras in the initial steps in malignant transformation of neuroendocrine cells.

The expression of glial fibrillary acidic protein (GFAP), vimentin, S-100 protein (S-100), HNK-1, myelin basic protein (MBP) and fibronectin was investigated immunohistochemically in 51 ethylnitrosourea (ENU)-induced neurinomas of the rat. Additionally, 90 transplantation tumors derived from ENU-induced neurinomas and the RN6 rat neurinoma cell clone were studied. Vimentin immunoreactivity was shown in 50/51 primary neurinomas and 60/90 transplantation tumors. In contrast, GFAP was expressed in only 23/51 primary tumors and in 5/90 transplantation tumors. In the RN6 neurinoma clone, vimentin and GFAP could be demonstrated both in vivo and in vitro. GFAP expression varied depending on the tumor localization, i.e., tumors of distal portions of peripheral nerves were more frequently GFAP positive than tumors of the spinal roots or of cranial nerves. The same tendency was observed for S-100. In the series of transplantation tumors S-100 and GFAP immunoreactivity decreased with increasing numbers of transplantation passages. Only individual cells in 5 primary tumors were HNK-1 positive and no MBP-immunoreactive cells were observed. Our results demonstrate that the expression of differentiation antigens in ENU-induced experimental neurinomas parallels the results reported for human neurinomas.

BDVI male rats were given a single i.p. dose of 80 mg/kg b.w. ethylnitrosourea (ENU), and each rat was then mated at weeks 1, 2, 3, 4 and 5 after treatment with 3 untreated females. A decrease in the fecundity of the treated males was observed, particularly when they were mated 5 weeks after ENU treatment. The average litter size was lower in the treated group, especially for females mated in week 4. No significant differences in pre- or post-weaning mortality were noted between control and treated groups. A slight, non-significant increase in the incidence of brain tumours was observed in the progeny of treated males compared with the controls. The incidence of thyroid tumours was significantly higher in controls but this difference disappeared when adjustment was made for litter effect and intralitter dependence.

A novel type of intoxication in Canada in 1987 was traced to consumption of cultivated mussels contaminated with the excitotoxin domoic acid. Studies carried out in rats and monkeys revealed that parenterally administered domoic acid induces in rats neuroexcitatory phenomena culminating in seizures. Monkeys respond with gagging, emesis and less clearly evident seizure activity. CNS damage consisting of dendrotoxic and gliotoxic edema and nerve cell degeneration occurs in structures of the limbic system and the retina in both species. CNS lesion distribution similarities in animals treated with domoic acid or kainic acid suggest that these excitotoxins share a common pathogenesis mediated by glutamic acid, a putative endogenous excitatory neurotransmitter.

Although the morphology of neural tumors induced in rats by N-ethyl-N-nitrosourea (NEU) and related alkylating agents has been extensively investigated, their histogenesis and the molecular basis of malignant transformation are still largely unknown. This review gives an account of the interaction of neurocarcinogenic agents with cellular DNA, the possible role of promutagenic O6-alkyldeoxyguanine and their deficient repair by the cerebral O6-alkylguanine-DNA alkyltransferase. A new experimental model is described in which neural tumors are induced in fetal brain transplants. Pregnant rats received a single iv dose of NEU (50 mg/kg) on the 14th day of gestation. One day later, suspensions were prepared from the fetal forebrain and stereotactically injected into the caudoputamen of adult rats. After additional exposure to NEU of the host animals 8 days and 9 weeks post transplantation, all rats developed brain tumors within the neural graft. Histopathologically, all neoplasms were classified as olidogdendrogliomas. Other neoplasms typically induced by NEU transplacentally (astrocytomas, mixed gliomas, ependymomas) were absent. The selective induction of oligodendrogliomas indicates that neoplastic transformation in the nervous system can occur in a differentiated glial cell or a precursor cell committed to oligodendrocytic differentiation, and that transformation of a pluripotential stem cell is not necessary. Transplacental exposure of the donor fetuses to NEU alone, i.e., without additional postgrafting exposure, did not produce brain tumors in any of the experimental animals indicating that in the microenvironment of fetal brain transplants the multistep development of gliomas requires additional mutational events. Malignant schwanomas perinatally induced by NEU carry a point mutation in the transmembrane domain of the neu gene. The mode of oncogene activation in NEU-induced CNS gliomas has not yet been elucidated. We have used cerebral grafting techniques to study the effects of known oncogenes on the developing nervous system, taking advantage of efficient gene transfer by replication-defective retroviral vectors and of the extraordinary capacity of fetal CNS to differentiate in and fully integrate with the host brain. Rats carrying transplants exposed in vitro to the polyoma medium T-antigen developed endothelial hemangiomas in the graft which often led to fatal cerebral hemorrhage within 13-50 days after transplantation. Introduction of the viral src gene caused astrocytic and mesenchymal tumors after latency periods of 2-6 months. Following infection of fetal donor cells with a vector encoding the v-myc oncogene, only a single embryonal CNS tumor was observed whereas exposure to v-H-ras produced a low incidence of gliomas.(ABSTRACT TRUNCATED AT 400 WORDS)

Ethylnitrosourea-induced central and peripheral nerve tumors in Sprague-Dawley rats were tested for GFAP (Glial Fibrillary Acidic Protein), S-100 protein, NSE (Neuron Specific Enolase) and Anti-Leu 7 (HNK-1) immunoreactivity utilizing the ABC method (avidin-biotin-complex) for GFAP, S-100 protein and NSE, and the PAP method (peroxidase-antiperoxidase) for Anti-Leu 7. Peripheral nerve neurinomas were consistently positive for S-100 protein and consistently negative for GFAP and Anti-Leu 7. Neurinomas would occasionally exhibit positive staining for NSE (2 of 55 tumors). The staining intensity for S-100 protein varied from strongly positive in differentiated neurinomas to weakly positive in anaplastic tumors. Neoplastic and reactive astrocytes exhibited positive staining for both S-100 protein and GFAP. Variation in the GFAP staining intensity of glial tumors correlated with the degree of differentiation as anaplastic tumors did not stain with the same intensity as their more differentiated counterparts. Oligodendrogliomas exhibited occasional immunoreactivity to S-100 protein (3 of 36 tumors). NSE reactivity in oligodendrogliomas was rarely observed (1 tumor in 36) and immunoreactivity against GFAP or Anti-Leu 7 was consistently absent. Anti-Leu 7 and NSE proved to be of little value in the classification of ENU-induced neural tumors.

The morphology of experimental tumors of the sympathetic nervous system in rabbits and hamsters induced by administration of nitrose compounds and the use of modifying factors were studied. The tumors were localized in the mediastinum, retroperitoneal space, adrenals and kidneys. A predominant involvement of the female animals was observed. Histological, histochemical and electron microscopic studies of 33 tumors of the sympathetic nervous system were carried out. By their degree of maturity the tumors were classified as ganglioneuromas, ganglioneuroblastomas and neuroblastomas. By their structure the experimental tumors were similar to the analogous neoplasias of man.

Two decades of research with resorptive neurocarcinogens firmly established the high potency of methyl and ethylnitrosourea (MNU and ENU) as neurocarcinogens, particularly in rats. There are significant differences in susceptibility to these agents among species. There are also differences among age groups. Fetuses are between 50 to 100 times more susceptible than adult rats. One single iv inoculation of 20-50 mg/kg ENU into pregnant rats may produce neurogenic tumors in 100% of the offspring. The tumors produced by these compounds have been well characterized morphologically, biologically, biochemically and histochemically. Tumors produced by both compounds are mostly gliomas and neurinomas (Schwannomas), however, clear differences exist between ENU and MNU produced neoplasms. Transplacental exposure to ENU generally results in a high number of anaplastic neurinomas and mostly differentiated gliomas (astrocytomas, oligodendrogliomas or mixed gliomas). In contrast, multiple exposures of adult rats to MNU result in a moderate number of mostly differentiated neurinomas and a high number of anaplastic gliomas. Tumors usually start out as well differentiated oligodendrogliomas or astrocytomas. As they grow larger, they become more mixed and anaplastic. In contrast to spontaneous gliomas in old rats, MNU and ENU-induced astrocytomas can be readily identified with well established biomarkers such as the S100 protein and particularly GFAP (glial fibrillary acidic protein). Neurinomas are also strongly positive for S100 protein. No reliable markers exist for oligodendrogliomas. Neurogenic tumors induced by MNU or ENU, as well as derived cell lines and clones from such tumors, have been successfully used as models for neurocarcinogenesis and therapeutic screening.(ABSTRACT TRUNCATED AT 250 WORDS)

In the first part of this paper, we show that intraperitoneal injection of adenosine into newborn mice causes multiple neural crest tumors, neural crest hyperplasia, and heterotopic melanin pigmentation. In the second part, we review published data to propose (1) that microtubule proteins, phosphorylated through the action of calmodulin-dependent kinase and cyclic adenosine monophosphate and the adenosine A2 receptor of neural crest cells, may participate in neurotransmission and (2) that at least some neural crest tumors may be associated with disorders of neurotransmission in embryonic neural crest cells.

Transplacental treatment with synestrol exerted a slight modifying effect on nitrosoethylurea-induced carcinogenesis in random-bred albino rats: prenatal treatment with synestrol reduced the rates of Leydig-cell and uterine tumor incidence to those of spontaneous tumors.

The tumorigenicity of neonatally administered N-ethyl-N-nitrosourea (ENU) was studied in four different inbred strain rats, that is Wistar/Furth (WF), Long-Evans (LE), F1 of Wistar/Furth and Long-Evans (F1) and Fischer 344 (F344) rats. All strains developed tumors of the nervous system with high incidence (97-100%) during 6 months of observation. The incidence of tumor of the central nervous system, including the brain (82-88%) and the spinal cord (53-76%), was high in all strains, but that of the peripheral nervous system, including the cranial nerve (21-89%) and the spinal root (13-93%), differed by strain. The peripheral nervous system of WF and F344 rats had a low susceptibility to the tumorigenic effect of ENU, but that of LE rats had a high susceptibility. Many brain tumors were induced in the temporal and frontal cortex and subcortex in all strains of rats. Spinal cord tumors were observed at all levels of the white matter of the spinal cord without any predilection site. Spinal root tumors were located in lumbosacral plexuses in WF and F344 rats, but in LE and F1 rats cervical and thoracic root tumors were also observed. Histological examination revealed that most of the brain and spinal cord tumors were oligodendroglioma, but in F344 rats about half of the brain tumors were mixed glioma. Epidermoid cysts of the lumbar spinal cord were observed only in F344 rats. Tumors of the peripheral nervous system were so-called anaplastic schwannoma.

N-Nitrosomethylurea (NMU) (20 mg/kg) was i.p. administered to rats on the 21st day of pregnancy. A decrease of glucose utilisation in the oral glucose tolerance test was found in 3 month old female progeny of NMU-treated rats. The serum insulin level did not differ from control, but serum cholesterol level was higher in offspring of NMU-treated rats. The ability of diethylstilboestrol to inhibit compensatory ovarian hypertrophy was decreased in female hemicastrated 3 month old rats whose mothers were treated with NMU. Postnatal administration of the antidiabetic drug buformin decreased the malignant neurogenic tumor incidence 3.5 times (to rats transplacentally treated with NMU).

Whole-body X-irradiation after neonatal injection with N-nitroso-N-ethylurea (ENU) significantly reduced the incidence of induced neurogenic tumors in inbred HMT rats kept for their complete life-span. After administration of 10 mg ENU/kg and 1.25 Gy X-radiation, the incidence of schwannomas but not of gliomas was reduced as compared to the incidence in rats given 10 mg ENU/kg only. In contrast, after administration of 4 mg ENU/kg, 1.25 Gy reduced the incidence of gliomas but not of schwannomas. Administration of 1.25 Gy alone induced a remarkably high incidence of rats with neurogenic tumors (20%). Latency of tumor detection was not significantly affected by radiation. Among the most frequently occurring nonneurogenic tumors, squamous cell carcinomas were reduced in incidence by treatment with ENU, 1.25 Gy X-radiation, or both combined. No treatment affected the incidence of pituitary or mammary tumors. There was a preponderance of ovarian tumors in rats given 4 mg ENU/kg + 1.25 Gy. An incidental finding was the occurrence of granular cell tumors in 7 rats from different treatment groups.

The precise role of the nerve growth factor protein (NGF) during the growth and development of the human nervous system is not determined. Although it appears to influence a number of neural functions, its mechanism of action is poorly understood. A number of researchers have proposed that NGF may be involved in several pathological conditions including cancer. It has been shown that NGF is secreted by certain sarcoma (23), neuroblastoma (113), and glioma (7,102,136) cell lines and can bind to neuroblastoma and metastatic melanoma cell lines (42). Neuroblastoma (136,181) and pheochromocytoma (165) cells in vitro can be induced by NGF to differentiate toward a morphologically "more benign" state and appropriate NGF treatment of rats can reduce the number of chemically induced gliomas and neurinomas (174,178). NGF can also reduce the growth of intracerebrally inoculated anaplastic glioma cells (172). Anti-NGF treatment of rats (178) and mice (179) can alter the tumor distribution observed following ethylnitrosourea or benzo(a)pyrene treatment (10). In humans, it has been reported that serum levels of NGF are usually elevated in persons "at risk" for neurofibromatosis (156). The precise nature of the NGF role is not known in these instances. Further understanding of the action of NGF could be of clinical importance.

Tumors of the central and peripheral nervous system were induced in BD-IX rats and transplanted serially. Both primary and transplanted tumors in different generations were cytologically analyzed, using primary explants in vitro. Four hundred and thirty single tumors were examined in vitro over th period 1969 to 1977, using the following methods: conventional aniline staining, special silver impregnation, supravital observation of cells by phase contrast microscopy, locomotion studies with time-lapse cinematography, and ultrastructural analysis from transmission and scanning electron microscopy. Cells grown in vitro were subdivided into the following groups, according to their morphology: (1) Apolar cells: Round cells only observed in rare tumors of the nasal cavity and sporadically in transplanted neurinomas; they are thought to represent cells from the reticular variant of neurinoma in the latter. (2) Bipolar cells occurred in two forms: As bipolar fibroblasts and as slender bipolar cells observed in explants of malignant neurinomas. The latter cells grow in parallel arrangements; their tentative interpretation as Schwann cells is consistent with their description in human neurilemomas. (3) Semipolar cells with one clear-cut edge and a broad ruffled membrane opposite. They are described as fibroblasts in the course of locomotion. (4) Multipolar cells, observed in several forms in primary and transplanted gliomas exclusively. Variants with long processes were seen in the first passages of intracerebrally transplanted tumors only; in later generations, all cells had short branching processes and little cytoplasm. Conclusions concerning the cytologic derivation of experimental tumors are discussed.

The threshold level of minimum carcinogenic dose of N-ethyl-N-nitrosourea (ENU) and the effect of dose on organ specificity were examined by continuous oral administration to both sexes of F344 rats of low doses of ENU at four concentrations (0.3, 1, 3 and 10 ppm) in the drinking water. ENU at 10 ppm selectively induced neurogenic tumors and tumors of the digestive tract, including duodenal tumors. Even at lower doses it enhanced the spontaneous development of some other tumors. A high dose of ENU (400 ppm) was previously found to induce duodenal tumors selectively. These results indicate that the organ specificity of ENU is influenced by the dose and that ENU has multi-potent carcinogenic activity in many organs and/or tissues. In this study, some specific tumors, such as those of the nervous system and digestive tract, seemed to require a minimum carcinogenic level of ENU (10 ppm) for their appearance. However, it seems that ENU is carcinogenic at much lower dose levels than 10 ppm because ENU enhanced the spontaneous development of some other tumors in many experimental groups. The so-called virtually safe doses inducing these specific tumors at a risk level of 10(-6) were calculated.

Since 1963 the observed mortality experience of BCNS cancers among rubber workers appears to be very comparable to that expected. A possible exception to this statement is the experience of one plant in Akron, Ohio, reported by Monson and Nakano. Excesses in earlier years may also be localized to one or two companies. The results of a case-control study did not support a hypothesized association of elevated BCNS cancer risk with exposures in the tire building/tire assembly segments of the rubber tire manufacturing process. The direction of future epidemiologic studies would benefit by the assembly of as large a number of cases as possible and should focus on calendar periods of exposure, make allowance for a latent period, and include retrospective industrial hygiene assessments of the specific exposures.

A chronic rodent study in F344 rats was conducted to investigate the promoting ability of phenobarbital (PB) on neurogenic tumors initiated by transplacental administration of ethylnitrosourea (ENU). Pregnant F344 rats were given a single intravenous dose of 3.5 mg ENU/kg or vehicle on the twentieth day of gestation. A total of 192 male offspring were divided into four groups: ENU-PB, ENU-control, PB-control, and control-control. Rats in ENU-PB and PB-control groups received 0.05% PB in their drinking water from four to 78 weeks of age. Nervous system tumors were induced only in animals exposed to ENU. The difference in the incidence of neuroectodermal tumors in rats that were ENU initiated only (13/37; 35%) compared to the incidence in rats that were initiated and given PB (13/57; 23%) was not statistically significant (p greater than 0.05). ENU-control and ENU-PB treatment groups exhibited no differences in tumor multiplicity or tumor latency. These results demonstrate that PB lacks promoting activity for neurogenic tumors in F344 male rats transplacentally exposed to ENU.

Distribution of DNA in cells of 28 primary ethylnitrosourea-induced tumours of the rat nervous system was studied by the Feulgen cytophotometry method. Out of them 20 had paradiploid DNA quantity, 3 tumours--hypodiploid and 4--hyperdiploid content of DNA. A high heterogeneity of the DNA quantity and the absence of expressed modal class were found only in one case. No correlation is found between the DNA distribution in gliomas and the stage of their malignancy.

Pregnant Sprague-Dawley rats were X-irradiated on the 16th day of gestation with 5 to 250 rads and given i.p. injections 4 days later with 10 mg ethylnitrosourea per kg. The offspring were observed over their life span for the appearance of neurogenic tumors. The frequency of animals surviving beyond 4 weeks of age that developed tumors was inversely related to X-ray dose. About 15% developed tumors after exposure to the largest doses, 39 to 46% after the intermediate doses, and 58 to 65% after the smallest doses; 69% tumors occurred after treatment with ethylnitrosourea alone. The reductions in tumor frequency were not due to the increased mortality rate of tumor-prone animals, either before or after the onset of tumor appearance. Mean offspring weight at 4 weeks and 4 months of age was inversely related to X-ray dose but was not significantly different in those animals later developing tumors from that in animals remaining tumor free. Mean time of tumor appearance and mean number of tumors per affected animal were unrelated to tumor frequency. It does not seem that the destruction of target cells is by itself sufficient to explain the results.

Experiments on rats were made to study the action of 7 anticarcinogenic substances administered postnatally for a long time (sodium selenite, retinol acetate, phenformin, amber acid, low-molecular polypeptide factors of the thymus, pineal gland, and bone marrow) on the transplacental carcinogenic effect of N-ethyl-N-nitrosourea (ENU) The polypeptide factors of the thymus and pineal gland and phenformin inhibited the development of nervous system and renal tumors induced transplacentally by ENU. The rest of the substances did not influence the transplacental carcinogenesis.

In a nested case-control study of workers employed between 1943 and 1977 at two nuclear facilities, we evaluated the possible association of primary CNS cancers with occupational exposure to chemicals. Seventy-two white male and 17 white female workers who, according to the information on death certificates, died of primary CNS cancers were identified as cases. For each case, four controls were matched on race, sex, facility at which initially employed (cohort), year of birth, and year of hire. Each job title/department combination was subjectively evaluated for potential exposure to each of 26 chemicals or chemical groups. Statistically significant associations were not found between CNS cancer deaths and any of the 26 chemicals. An increased risk of CNS cancer occurrence was observed among subjects employed for more than 20 yr (OR = 7.0, 95% CI = 1.2,41.1, cases = 9).

Transplanted tumor lines are useful to study open questions in human pathology and clinical research, particularly with the evaluation of therapeutic measures. Transplantation tumor lines derived from neoplasms in the nervous system originally induced with resorptive carcinogens are considered to be useful for these purposes. In this study observations on the histological pattern of original and intracerebrally transplanted new induced spinal cord tumors, mainly in early passages, has been investigated with the aim to improve the usefulness of the experimental model.

To study the late effects of early postnatal treatment with N-ethyl-N-nitrosourea (ENU) preceded by X irradiation to the head, 226 neonatal CD rats were divided into six groups which received the following treatment: (1) 500-rad X irradiation to the head on the third postnatal day (pnd); (2) injection ip with 30 mg/kg ENU on the fourth pnd; (3) injection ip with 30 mg/kg ENU on the seventh pnd; (4) a combination of 500-rad X irradiation to the head on the third pnd, followed by ip 30 mg/kg ENU on the fourth pnd; (5) a combination of 500-rad X irradiation to the head on the third pnd, followed by ip 30 mg/kg ENU on the seventh pnd; and (6) untreated controls. The results indicate that (1) X irradiation to the head alone significantly extended the life span of females compared to that of control females, and did not affect survival of males; (2) X irradiation did not influence the latent period or mortality from neurogenic tumors when ENU was given 1 or 3 days afterward; (3) ENU itself was a factor in shortening latent periods for mammary tumors; (4) X irradiation alone did not increase the incidence of mammary tumors, and revealed no protective effect on the ENU-induced mammary carcinogenesis; (5) X irradiation increased the prevalence of pituitary tumors in the females; (6) no enhancement of pituitary tumors by ENU was observed: and (7) there was a statistically significant association of pituitary and mammary tumors in females.

The study was concerned with the influence of a long-term postnatal treatment with an antidiabetic biguanide-phenformin and a biologic stimulating agent-succinic acid upon the realization of transplacental carcinogenic effect of N-ethyl-N-nitrosourea (ENU) in rats. Phenformin treatment inhibited the development of induced tumors in the nervous system and kidneys, significantly decreased the total incidence and multiplicity of these tumors, the incidence of brain and spinal cord tumors and multiplicity of brain tumors. Succinic acid did not influence the transplacental carcinogenic effect of ENU.