Medulloblastomas and other neural tumours in mice treated neonatally with N-ethyl-N-nitrosourea

Beauty product-related exposures and childhood brain tumors in seven countries: results from the SEARCH International Brain Tumor Study

Data from 1218 cases of childhood brain tumors (CBT) diagnosed between 1976 and 1994 and 2223 matched controls from the general population were included in an analysis of maternal beauty product exposure and beauty-related employment in 9 centers in 7 countries. A 50% increased odds ratio (OR) [95% confidence interval (CI) = 1.0-2.1] for CBT was observed among children of mothers who were exposed via personal use of and/or possible ambient contact with beauty products during the 5 years preceding the index child's birth compared with children of mothers never exposed to beauty products during this time period. Overall maternal personal use of hair-coloring agents in the month before or during the pregnancy of the index child's birth was not associated with CBT (OR = 1.0, CI = 0.83-1.3) or with astroglial (OR = 1.1, CI = 0.85-1.4), PNET (OR = 1.0, CI = 0.71-1.5) and other glial subtypes (OR = 1.0, CI = 0.62-1.0). Similarly, no statistically increased ORs or discernable pattern of risk estimates were observed for period of use or for number of applications per year for maternal personal use of hair-coloring agents overall or by histologic type. Among children born on or after 1980, increased ORs for CBT were associated with maternal non-work-related exposure to any beauty products (OR = 2.6, CI = 1.2-5.9), hair-dyes (OR = 11, CI = 1.2-90), and hair sprays (OR = 3.4, CI = 1.0-11). No overall increased OR for CBT was observed among children of mothers employed in beauty-related jobs during the 5 years preceding the index child's birth compared with those who reported no beauty-related employment. In general, other specific beauty product-related exposures were not associated with increased ORs for CBT. Data from our study provide little evidence of an increased risk for CBT with mothers' exposures to beauty products.

Development of nitrosourea-induced brain tumours--with a special note on changes occurring during latency

Nitrosourea compounds fulfil the requirements of ideal carcinogens, in that they produce a high incidence of tumours selectively and consistently in the nervous system, they induce neoplasms that have morphological and biological similarities to naturally occurring neural tumours in man and animals and they represent an environmental hazard. N-Ethyl-N-nitrosourea (ENU) has a preferential transplacental and neonatal action, a single intravenous or intraperitoneal injection inducing an almost 100% incidence of neural neoplasms. Transplacental carcinogenesis by ENU provides an ideal experimental model in which the sequential development of brain tumours can be studied. Investigations of the early stages of brain carcinogenesis induced by transplacentally administered ENU have shown that: (1) the earliest histologically detectable changes appear in 8-wk-old animals and are composed of stem cells; (2) these early lesions are frequently multiple and become larger with increasing age; (3) they are not distributed at random, but occur in areas in which tumours develop later; (4) the carcinogens endow the cells, even only 2 days after exposure, with a malignant potential which may subsequently become manifest either in vivo or in culture; (5) half-way through latency, malignant cells are present in the brain; (6) the emergence of the malignant phenotype in cultured brain cells is a stepwise process which culminates in the concomitant appearance of tumorigenicity and invasiveness.

Fetal origin of the medulloblastoma: evidence from growth analysis of two cases

Growth analysis of medulloblastomas was performed in two children. They initially manifested symptoms at the age of 3 years and 9 months and at the age of 2 months respectively. Computerized tomography (CT) scans were obtained at different points in each case. The growth curves were drawn on a semilogarithmic graph by calculating the tumor volume on CT on the assumptions that the tumor started from a single tumor cell and that the growth rate was constant. By extrapolating the curves back, tumor inception was estimated to have occurred respectively at the 14-23rd week and at the 16-17th week of gestation. Additional cell kinetic data were obtained from DNA analysis of surgical pathology specimens. Calculated cell-cycle times were 22-32 h for both cases. The S phases comprised 26.3% and 27% and the G0G1 phases 66.8% and 62% of the cell cycle, respectively, for case 1 and 2. Assuming a labelling index of 14%, the cell loss factors were estimated to be 97% and 74% (case 1 and case 2 respectively). The seventeenth week of gestation in humans corresponds to the timing of events occurring postnatally at days 3-18 in the developing cerebella of rodents, i.e., at the time of maximal activity in the migration and differentiation of the cells of the fetal external granular layer. Medulloblastomas have been experimentally induced in rodents by the injection of oncogenic viruses during the neonatal period, and statistical data on the epidemiology of human medulloblastomas have suggested a possible association with the contamination of polio vaccine by the SV 40 virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Nucleic acids and protein in brains and cerebella of rats transplacentally exposed to ethylnitrosourea

Female rats were injected (IP) with either 15, 60, 100, or 150 mg/kg N-ethyl-N-nitrosourea (ENU) on gestation day 18. The neurochemical development of the whole brain and the cerebellum was studied in 21- and 60-day old offspring; pups from mothers subjected to 150 mg/kg were examined only at 21 days. Brain weights were significantly reduced in all ENU-exposed groups at 21 days, and the 60 mg/kg group at 60 days. Whole brain DNA and protein concentrations of most ENU groups were elevated at 21 days and RNA content and RNA/DNA ratios were subnormal. Deficits in whole brain DNA content were observed in all ENU groups on day 60. Cerebellar weight was reduced in the 60 and 150 mg/kg groups on day 21 and in the 100 mg/Kg group on day 60. At 21 days, reductions in cerebellar DNA and RNA concentrations and contents were often recorded in several ENU groups. Cerebellar DNA concentration and content of the 60 and 100 mg/kg groups remained subnormal at 60 days of age. In general, a dose-response effect was evident in the number and magnitude of neurochemical alterations produced by ENU. These data suggest that transplacental exposure to ENU, a potent neurotropic carcinogen, affects the biochemical maturation of the brain.

Glial-mesenchymal tropism of in vivo avian sarcoma virus neuro-oncogenesis in rats

Intracerebral inoculation of avian sarcoma virus (ASV) in postnatal animals induces gliomas and sarcomas but no neuronal tumors. High titer Bratislava-77 strain ASV was inoculated intracerebrally in fetal F-344 rats between 17 and 20 days of gestation: a time of active neuronal proliferation. Following birth inoculated rats developed gliomas and sarcomas but no neuronal tumors. The results are evidence that the glial-mesenchymal tropism of in vivo ASV neuro-oncogenesis is independent of stage of neurocytodifferentiation at inoculation.

Excision of O6-methylguanine from DNA of various mouse tissues following a single injection of N-methyl-Nitrosourea

The persistence of O6-methylguanine produced by a single dose of N-methyl-N-nitrosourea (MNU) was determined in DNA of various murine tissues and compared with the location of tumours induced by MNU and related alkylating carcinogens in this species. A/J and C3HeB/FeJ mice received a single intravenous injection of MNU (10 mg/kg) and were killed at different time intervals ranging from 4 h to 7 days. The rate rate of loss of O6-methylguanine from brain DNA was considerably slower than from liver DNA; tumours have been found in both organs after administration of MNU and other alkylnitrosoureas. There was no difference in the rate of excision from cerebral DNA of A/J and C3HeB/FeJ mice, although these strains differ significantly in their susceptibility to the neurooncogenic effect of MNU and related carcinogens. Excision of O6-methylguanine from hepatic DNA was significantly slower in A/J than in C3HeB/FeJ mice; both strains habe been found to develop hepatic carcinomas following MNU administration. Seven days after the injection of 3H-MNU, O6-methylguanine concentrations were highest in brain and lung DNA, lowest in the liver, and intermediate in kidney, spleen, small intestine and stomach. The lung is a principal target organ for tumour induction by MNU and other carcinogens in mice; however, neural tumours are usually induced at a low incidence. The results obtained do not contradict the hypothesis that O6-alkylation of guanine in DNA is a critical event in the initiation of tumour induction by alkylating agents. However, the location of tumours produced in mice does not seem to depend solely on the formation and persistence of O6-alkylguanine in DNA.