Effectiveness and safety of everolimus treatment in patients with tuberous sclerosis complex in real-world clinical practice

BACKGROUND

The randomised double-blinded placebo-controlled EXIST-1-3 studies have showed everolimus effective with adverse effects reported as acceptable in treatment of symptoms in patients with tuberous sclerosis complex (TSC), although evidence of outcomes in clinical practice remains limited. This study aimed to investigate, in clinical practice, the effectiveness and safety of everolimus for epilepsy, renal angiomyolipoma (rAML), and subependymal giant cell astrocytoma (SEGA) in patients with TSC.

RESULTS

The study included 64 patients with TSC (median age: 19, range 0.9-54 years) receiving everolimus treatment (Norway: n = 35; Denmark: n = 29). Among 45 patients with epilepsy, 14 (31%) were responders experiencing ≥ 50% reduction in seizure frequency in the last 3 months of treatment compared with the last 3 months before treatment. Nineteen (42%) patients changed their anti-seizure medications (ASMs). Responders were more common among patients < 18 years (46%) than among patients ≥ 18 years (14%, p = 0.03). In 29 patients with rAML, everolimus reduced (≥ 30% decrease) and stabilized (< 20% increase, ≤ 30% decrease) longest diameter of rAML in 38% and 59%, respectively, after a mean treatment duration of 37 months. SEGA volume was reduced in three patients by 71%, 43%, and 48% after 39, 34, and 82 months. Adverse effects were reported in 61 of 64 patients (95%) after a median treatment duration of 31 months (range 0-106), with oral ulceration/stomatitis (63%) and upper respiratory tract infections (38%) being the most common. The most common laboratory abnormalities were increased cholesterol (41%), anaemia (30%), and leucopoenia (25%). Grade 3-4 adverse effects were reported in 36% of cases, and life-threatening conditions were reported in two patients. Nine patients discontinued everolimus treatment.

CONCLUSIONS

Seizure reduction in this study sample was consistent with results from EXIST, but might be lower than expected, given that changes in concomitant ASMs are part of clinical practice. Seizure reduction was associated with younger age. As with EXIST, everolimus reduced or stabilised rAML size in most patients. SEGA volume was reduced in all three patients. Close follow-up is needed for this group, especially for children and patients who may not be able to report adverse effects.

[Tumour induction by ethylnitrosourea in the central nervous system]

INTRODUCTION

Experimental central nervous system (CNS) tumours have been proposed as a useful model for the study of oncogenesis, epiphenomena related to cancer and for the design of new therapeutic strategies.

DEVELOPMENT

The administration of chemical substances is one of the most commonly-used methods to induce CNS neoplasms. N-ethyl-N-nitrosourea (ENU) belongs to the nitrosourea family, a wide group of alkylating agents that are able to induce brain tumours in litters after transplacentary administration at the 15th day of pregnancy. This nitrogenous urea compound has a high mutation inducibility affecting the expression of oncogenes such as p53, neu/erbB-2 and Ras. Prenatal exposition of Sprague Dawley rats to ENU induces intra-axial tumours of glial lineage and extra-axial malignant schwannomas. Although the precise mechanism of tumour induction is unclear, it is known to affect cell differentiation of primitive neuroepithelium from the subventricular plate generating oligodendrogliomas, astrocytomas, mixed gliomas or ependimomas.

CONCLUSION

The transplacentary administration of ENU induces the development of gliomas and schwannomas that are similar to those found in humans. Animal models are necessary and useful for further studies to get an early diagnosis and to establish correct therapeutic indications.

Effects of lipid association on lomustine (CCNU) administered intracerebrally to syngeneic 36B-10 rat brain tumors

A syngeneic, intracerebral rat brain tumor model was developed and characterized and then used to evaluate the therapeutic enhancement of lipid-associated 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU). The Fisher rat glioma cell 36B-10 (100,000-500,000 cells) was implanted intracranially to Fisher F-344 rats into the caudate nucleus. Animals treated with lipid-associated CCNU showed a 2- to 10-fold decrease in tumor size compared with animals treated with free CCNU, indicating that lipid association increases the therapeutic index of intracerebral CCNU treatment. Moreover, the syngeneic rat brain tumor model may be useful for evaluation of other therapeutic modalities.

Abnormal cortical cells and astrocytomas in the Eker rat model of tuberous sclerosis complex

PURPOSE

In patients with tuberous sclerosis complex (TSC), a wide range of neurologic abnormalities develop, including mental retardation and seizures. Brains from TSC patients are characterized by the presence of cortical tubers, large dysmorphic neurons, and abnormal cytomegalic cells. Although analysis of human TSC brain samples led to the identification of these abnormal cell types, very little is known about how these cells function. In an effort to model TSC-associated CNS abnormalities (and ultimately to analyze the electrophysiologic properties of abnormal cells), we examined Eker rats carrying a Tsc2 mutation. Anatomic studies, including standard histologic stains and immunocytochemistry, were performed on young Eker rats exposed to a carcinogen in utero or aged untreated Eker rats (18-24 months old).

METHODS

Pregnant TSC2+/- females were injected once a day with hydroquinone (HQ), and offspring were killed at postnatal day P14 or P28. Coronal tissue sections throughout the CNS were prepared and stained for cresyl violet. In separate studies, brains of old untreated Eker rats were sectioned for anatomic analysis by using standard immunohistochemical techniques.

RESULTS

Tissue sections stained with cresyl violet did not reveal any gross differences between HQ-treated Eker (Tsc2Ek/+) rats and siblings (Tsc2+/+). However, two classes of abnormal giant cells were observed in brain sections from untreated aged Eker rats: (a) large dysmorphic pyramid-like cells immunoreactive for NeuN, tuberin, and EAAC-1 in layers IV-VI; and (b) abnormal cytomegalic cells immunoreactive for glial fibrillary acidic protein (GFAP), vimentin, and nestin in deep cortical layers or along the white matter. In addition, large subependymal astrocytomas were observed in four animals.

CONCLUSIONS

Our data suggest that cortical tuber formation in Eker rats is a rare event and that prenatal exposure to a nongenotoxic carcinogen such as HQ is not sufficient to induce tuber formation. However, with advanced age, an increased likelihood of astrocytoma formation and the emergence of dysmorphic neurons and cytomegalic cells in the Eker rat brain might exist; each of these abnormalities mimics those seen clinically and could contribute to neurologic problems associated with TSC. Further analysis of this rodent model may be warranted.

Household water source and the risk of childhood brain tumours: results of the SEARCH International Brain Tumor Study

BACKGROUND

The period in utero is a time of increased vulnerability. Offspring of pregnant women exposed to carcinogenic substances in drinking water may be more likely to develop cancer. We examined whether household water source and the presence of nitrates or nitrites in residential water were associated with increased risks of childhood brain tumours (CBT).

METHODS

We used data from a multicentre, case-control study with maternal information on residential water source, and nitrate/nitrite levels of tap water measured by dipstick. Subjects included 836 CBT cases and 1485 controls from five countries.

RESULTS

The risks of CBT associated with reliance on well water (versus public water) during pregnancy varied widely, with significantly increased risks noted in two (of seven) regions and a decreased risk observed in one region. CBT risk did not increase with increasing nitrate levels. However, our results based on tap water tested in the pregnancy residences suggest the risk of astrocytoma may be associated with increasing levels of nitrite (odds ratio [OR] = 4.3, 95% CI: 1.4, 12.6 for nitrite levels of 1-<5 mg/l nitrite ion; OR = 5.7, 95% CI: 1.2, 27.2 of nitrite > or =5 mg/l).

CONCLUSIONS

These results should be interpreted with caution because women's recollection of water sources may have contained inaccuracies, and nitrate and nitrite measurements, available for only a portion of subjects, were often obtained years after the pregnancies occurred. However, our results suggest a need for closer evaluation of well water content in some regions and the possibility that a nitrite-related water exposure may be associated with CBT.

Parental occupational exposure to pesticides and childhood brain cancer

The authors examined the risk of childhood brain cancer in relation to parental exposure to classes of pesticides among 154 children diagnosed with astrocytoma and 158 children diagnosed with primitive neuroectodermal tumors (PNET) in the United States and Canada between 1986 and 1989. Controls were selected by random digit dialing and were individually matched to cases by race, age, and geographic area. Each job in the fathers' work history and the usual occupation of mothers were assigned a probability, intensity, and frequency of exposure to insecticides, herbicides, and agricultural and nonagricultural fungicides. Elevated risks of astrocytoma were found for paternal exposure (ever vs. never) to all four classes of pesticides (odds ratio (OR) = 1.4-1.6). An increased risk of PNET was observed for only herbicides (OR = 1.5). For mothers, odds ratios for astrocytoma were elevated for insecticides, herbicides, and nonagricultural fungicides (OR = 1.3-1.6) but not agricultural fungicides (OR = 1.0). No indication was found of an increased risk for PNET. There was little indication for an association with cumulative and average parental exposure. Most risk estimates were around unity, and exposure-response patterns were absent. Overall, it seems unlikely that parental exposure to pesticides plays an important role in the etiology of childhood brain cancer.

Never forget the risks of immunosuppression

It has been widely reported in the literature that malignant neoplasms are a recognised complication of immunosuppression following organ transplantation. These days, immunosuppressive drugs are being used for many conditions outside the transplant setting. A case of a de novo astrocytoma in a patient on long-term immunosuppression for psoriatic arthritis is described.

Three-generation reproduction study of rats receiving acrylonitrile in drinking water

Acrylonitrile, a high volume organic chemical, was tested for reproductive effects in a three generation drinking water study with two matings per generation. Sprague-Dawley rats were exposed to acrylonitrile in drinking water at 0, 100, or 500 ppm. This corresponds to 0, 11+/-5 and 37+/-10 mg/kg, respectively, for males and 0, 20+/-3 and 40+/-8 mg/kg per day for the females, respectively. Water consumption was reduced in F0 rats in the 100 and 500 ppm groups. At 500 ppm, acrylonitrile reduced body weight gain and food intake of the first generation parental rats (F0). These parameters were not investigated at subsequent generations. The pup survival (both viability and lactation indices) was reduced at the 500 ppm treatment level in both matings of all three generations. Fostering the 500 ppm pups onto untreated mothers following the second mating lessened mortality, suggesting a maternal effect consistent with decreased water consumption. There was no remarkable change in the reproductive capacity in any of matings in rats at the 100 ppm concentration. In contrast, in all three generations, the body weights of the pups of the 500 ppm treatment level were reduced on Day 21 at both matings. No adverse findings were observed in the tissues of a limited number of third generation weanlings (F3b) upon gross and microscopic evaluation. No effect on the sciatic nerve was evident among the adult female rats held for 20 weeks after weaning of the second litter. There was a dose-related effect of acrylonitrile on gross masses in female rats at each parental generation held 20 weeks after the weaning of the second litter. Histopathological evaluation of these dams showed an increase in astrocytomas and zymbal gland tumors.

Dietary restriction reduces angiogenesis and growth in an orthotopic mouse brain tumour model

Diet and lifestyle produce major effects on tumour incidence, prevalence, and natural history. Moderate dietary restriction has long been recognised as a natural therapy that improves health, promotes longevity, and reduces both the incidence and growth of many tumour types. Dietary restriction differs from fasting or starvation by reducing total food and caloric intake without causing nutritional deficiencies. No prior studies have evaluated the responsiveness of malignant brain cancer to dietary restriction. We found that a moderate dietary restriction of 30-40% significantly inhibited the intracerebral growth of the CT-2A syngeneic malignant mouse astrocytoma by almost 80%. The total dietary intake for the ad libitum control group (n=9) and the dietary restriction experimental group (n=10) was about 20 and 13 Kcal x day(-1), respectively. Overall health and vitality was better in the dietary restriction-fed mice than in the ad libitum-fed mice. Tumour microvessel density (Factor VIII immunostaining) was two-fold less in the dietary restriction mice than in the ad libitum mice, whereas the tumour apoptotic index (TUNEL assay) was three-fold greater in the dietary restriction mice than in the ad libitum mice. CT-2A tumour cell-induced vascularity was also less in the dietary restriction mice than in the ad libitum mice in the in vivo Matrigel plug assay. These findings indicate that dietary restriction inhibited CT-2A growth by reducing angiogenesis and by enhancing apoptosis. Dietary restriction may shift the tumour microenvironment from a proangiogenic to an antiangiogenic state through multiple effects on the tumour cells and the tumour-associated host cells. Our data suggest that moderate dietary restriction may be an effective antiangiogenic therapy for recurrent malignant brain cancers.

Evaluation of ENU-induced gliomas in rats: nomenclature, immunochemistry, and malignancy

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.

Examination of low-incidence brain tumor responses in F344 rats following chemical exposures in National Toxicology Program carcinogenicity studies

Neoplasms in the brain are uncommon in control Fischer 344 (F344) rats; they occur at a rate of less than 1% in 2-yr toxicity/carcinogenicity studies. Furthermore, only 10 of nearly 500 studies conducted by the National Toxicology Program (NTP) showed any evidence of chemically related neoplastic effects in the brain. Generally, the brain tumor responses were considered equivocal, because the characteristics of potential neurocarcinogenic agents (such as statistically significant increased incidences, decreased latency and/or survival, and demonstration of dose-response relationships) were not observed. A thorough examination, including comparisons with a well-established historical database, is often critical in evaluating rare brain tumors. Chemicals that gave equivocal evidence of brain tumor responses were generally associated with carcinogenicity at other sites, and many chemicals were mutagenic when incubated with metabolic activating enzymes. Other factors that were supportive of the theory that marginal increases in brain tumor incidence were related to chemical exposure were that (a) some of the tumors were malignant, (b) no brain neoplasms were observed in concurrent controls from some studies, and/or (c) brain tumors were also seen following exposure to structurally related chemicals. In 2-yr studies in F344 rats (studies conducted by the NTP), equivocal evidence of carcinogenicity was observed for the following 9 chemicals: isoprene, bromoethane, chloroethane, 3,3'-dimethylbenzidine dihydrochloride, 3,3'-dimethoxybenzidine dihydrochloride, furosemide, C.I. direct blue 15, diphenhydramine hydrochloride, and 1-H-benzotriazole. Glycidol was the only chemical evaluated by the NTP with which there was clear evidence of brain tumor induction in F344 rats. Clarification of the potential neurocarcinogenic risks of chemicals that produce equivocal evidence of a brain tumor response in conventional 2-yr rodent studies may be aided by the use of transgenic mouse models that exhibit genetic alterations that reflect those present in human brain tumors as well as by the use of in utero exposures.

CNS tumors and exposure to acrylonitrile: inconsistency between experimental and epidemiology studies

Acrylonitrile is a potent CNS tumorigen in rats leading to concern that it may be a tumorigen in humans. There have been 12 epidemiology studies of 37,352 workers exposed to acrylonitrile which evaluate CNS cancers. We summarize and evaluate these epidemiology studies for CNS cancers using the methods of meta-analysis. Our analyses indicate that workers with acrylonitrile exposure have null findings for CNS cancer (relative risk = 1.1, 95% confidence interval 0.8-1.5), which are in stark contrast to the projected risk to humans using the rat findings (relative risk = 3.5, 95% confidence interval 3.0-4.0). We discuss several explanations for the inconsistency between animal and human findings, including the possibility that the acrylonitrile-induced rat CNS tumors may not be relevant to humans. Given the rarity of CNS tumors in humans and a lack of understanding of the causal mechanisms of these tumors in rats, however, a more definitive conclusion will have to await additional experimental and observational data. Nevertheless, the epidemiology evidence indicates that acrylonitrile is not a potent CNS tumorigen.

Changes in VEGF expression and in the vasculature during the growth of early-stage ethylnitrosourea-induced malignant astrocytomas in rats

Vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, may be important as a mediator of brain tumour progression. However, it is still not clear whether VEGF plays a causative role in the early stage of glioma development. We investigated the relationship between VEGF protein expression (as assayed by immunohistochemistry) and different morphological parameters reflecting tumour progression (tumour diameter, vascular density and vascular diameter) in tumours at various stages. As a tumour model, ethylnitrosourea (ENU)-induced rat malignant astrocytoma was used. Tumours were classified by size and level of vascularity estimated by the von Willebrand factor (vWF) staining. Tumours less than 10 mm in diameter were designated early stage neoplastic lesions. All 34 early astroglial tumours were found to be VEGF positive. Increase in the VEGF immunopositive rate of tumour cells correlated significantly with increase in vascular density and vascular diameter. We suggest that VEGF induces angiogenesis and growth of microvessels, promoting growth of the early stage malignant astrocytoma.

Increased telomerase activity and absence of p53 mutation in oligoastrocytomas induced by N-ethyl-N-nitrosourea in rats

The question of whether the changes in telomerase activity and/or the alteration of the p53 gene are involved in the development of oligo-astrocytomas induced by N-ethyl-N-nitrosourea (ENU) in rats was addressed. Telomerase activity levels of oligo-astrocytomas, including early neoplastic lesions, were significantly increased as compared to the normal controls, correlating with the degree of malignancy. In contrast, no mutations of p53 exons 5-7 were found in early neoplastic lesions or oligo-astrocytomas. These results indicate that the activation of telomerase occurs during astrocytoma carcinogenesis and contributes to the development of brain tumors, but the alterations of p53, at least on exons 5-7, may not be involved in this process.

Cancer risk and residential proximity to cranberry cultivation in Massachusetts

OBJECTIVES

This study evaluated the relationship between cancer risk and residential proximity to cranberry cultivation.

METHODS

A population-based case-control study was conducted. Cases, diagnosed during 1983 through 1986 among residents of the Upper Cape Cod area of Massachusetts, involved incident cancers of the lung (n = 252), breast (n = 265), colon-rectum (n = 326), bladder (n = 63), kidney (n = 35), pancreas (n = 37), and brain (n = 37), along with leukemia (n = 35). Control subjects were randomly selected from among telephone subscribers (n = 184), Medicare beneficiaries (n = 464), and deceased individuals (n = 723).

RESULTS

No meaningful increases in risk were seen for any of the cancer sites except for the brain. When latency was considered, subjects who had ever lived within 2600 ft (780 m) of a cranberry bog had a twofold increased risk of brain cancer overall (95% confidence interval [CI] = 0.8, 4.9) and a 6.7-fold increased risk of astrocytoma (95% CI = 1.6, 27.8).

CONCLUSIONS

Residential proximity to cranberry bog cultivation was not associated with seven of the eight cancers investigated; however, an association was observed with brain cancer, particularly astrocytoma. Larger, more detailed studies are necessary to elucidate this relationship.

Maternal exposure to N-nitrosatable drugs as a risk factor for childhood brain tumours

BACKGROUND

Animal models suggest that compounds containing a nitrosyl group (N-nitroso compounds (NNO)) can act as potent transplacental carcinogens. Many common drug formulations have the potential to undergo nitrosation in vivo. The association between maternal use of nitrosatable drugs during pregnancy and development of brain tumours in the offspring was examined in a SEER-based case-control study.

METHODS

Maternal exposure to nitrosatable drugs during pregnancy was compared among 361 childhood brain tumour cases and 1083 matched controls recruited through random-digit dialing.

RESULTS

There was no increase in risk observed for childhood brain tumours overall (OR = 1.15; 95% CI: 0.69-1.94) or for astrocytomas individually (OR = 1.16; 95% CI: 0.50-2.69). A slight elevation in risk was noted for medulloblastomas (OR = 1.47; 95% CI: 0.28-7.62) and 'other' tumours (OR = 1.27; 95% CI: 0.56-2.86), however, both estimates were based on small numbers.

CONCLUSIONS

Our findings suggest that no increased risk of childhood brain tumours was associated with maternal exposure to nitrosatable drugs. The study results should be viewed with caution given the imprecision of the point estimates as well as the lack of data on specific timing and dosage of exposure and degree of nitrosatability of drugs taken.

Occupational exposure to chlorinated aliphatic hydrocarbons and risk of astrocytic brain cancer

Chlorinated aliphatic hydrocarbons (CAHs) were evaluated as potential risk factors for astrocytic brain tumors. Job-exposure matrices for six individual CAHs and for the general class of organic solvents were applied to data from a case-control study of brain cancer among white men. The matrices indicated whether the CAHs were likely to have been used in each industry and occupation by decade (1920-1980), and provided estimates of probability and intensity of exposure for "exposed" industries and occupations. Cumulative exposure indices were calculated for each subject. Associations of astrocytic brain cancer were observed with likely exposure to carbon tetrachloride, methylene chloride, tetrachloroethylene, and trichloroethylene, but were strongest for methylene chloride. Exposure to chloroform or methyl chloroform showed little indication of an association with brain cancer. Risk of astrocytic brain tumors increased with probability and average intensity of exposure, and with duration of employment in jobs considered exposed to methylene chloride, but not with a cumulative exposure score. These trends could not be explained by exposures to the other solvents.

[A retrospective evaluation of exposure to dichloromethane by using a job-exposure matrix]

The impact of three features of a job-exposure matrix has been tested in a case-control study that evaluated the association of occupational exposure to dichloromethane and astrocytic brain cancer. These features were probability of exposure, an exposure assessment by decades, and the use of a more specific coding system of industries and occupations. The introduction of each feature had a striking effect on the estimate of relative risk. The odds ratio increased from 1.47 with none of these features, to 2.47 with high probability of exposure, to 4.15 with high probability of exposure and the specific coding system, to 6.08 with all features combined. These results indicate that job-exposure matrices efficacy in reducing the degree of exposure misclassification may be greatly improved by the introduction of these features.

Effects of three features of a job-exposure matrix on risk estimates

We tested the impact of three features of a job-exposure matrix on risk estimates in a case-control study that evaluated the association of methylene chloride and astrocytic brain cancer. These features were probability of use of the agent; the consideration of decade of predominant use of methylene chloride within each occupation; and the use of a more specific industrial-occupational coding system. We compared the risk estimates obtained with and without these features. The introduction of each feature had a striking effect on the estimate of relative risk. The odds ratio ranged from 1.47 with none of these features, to 2.47 with high probability of exposure within industry and occupation, to 4.15 with high probability of exposure and specific industrial-occupational coding, to 6.08 with the three features together. These results indicate that the degree of exposure misclassification can be reduced by the introduction of these features into the job-exposure matrix.

Measurement of blood-brain barrier permeability in a tumor model using magnetic resonance imaging with gadolinium-DTPA

Sequential MR imaging with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) and sequential measurements of plasma Gd-DTPA concentration by inductively coupled plasma atomic emission spectroscopy (ICP-AES) were used to estimate the blood-to-tissue transport coefficient (Ki) in the 36B-10 rat glioma model. For these measurements, tissue Gd-DTPA concentration was estimated from tumor enhancement by correlation with calibration measurements obtained by ICP-AES analysis of tumor tissue. The 14 animals for which Ki was calculated can be grouped into those imaged at 11 days following tumor implantation, at 13-18 days, and at 20 days. The mean (+SEM) Ki values for these groups were 1.1 + 0.24, 9.2 + 0.8, and 13.4 + 1.7 ml/kg-min, respectively. These results correspond well with published data obtained by quantitative autoradiography. It is concluded that frequent sequential imaging and a graphical approach to Ki calculation are promising methods for determining the blood-to-tissue transport coefficient noninvasively by contrast-enhanced MRI.

Brain cancer and farming in western Canada

A cohort study of the mortality experience (1971-1987) of male Canadian prairie farmers has been conducted. This involved linking the records of 156,242 male Alberta, Saskatchewan and Manitoba farmers identified on the 1971 Census of Agriculture and the corresponding Census of Population to mortality records. Exposure indices for individual farm operators were derived from 1971 Census of Agriculture records. Cancer histologies for brain cancer cases were obtained from the Canadian National Cancer Incidence Database and from Provincial Cancer Registries. A statistically significant association was noted between risk of dying of glioblastomas and increasing fuel/oil expenditures (test for trend p = 0.03, top quartile relative risk = 2.11, 95% confidence interval = 0.89-5.01). No significant association was found between brain cancer and either education or mother tongue. However, low income was associated with a significantly reduced risk of brain cancer mortality.

Dyke Award Paper. Kinetics of pathologic blood-brain-barrier permeability in an astrocytic glioma using contrast-enhanced MR

PURPOSE

The feasibility of measuring blood-brain barrier permeability was studied in a 36B-10 brain glioma model in rats.

MATERIALS AND METHODS

In stage I of our study, sequential MR images of glioma-implanted rats were obtained following intravenous administration of three contrast agents of different molecular sizes--Gd-DTPA, polylysine-(Gd-DTPA), and albumin-(Gd-DTPA). In a second set of experiments, sequential MR imaging with Gd-DTPA, quantitative measurements of plasma Gd-DTPA concentration, and postmortem tumor Gd-DTPA measurements were used to estimate the blood-to-tissue transport coefficient (Ki) in the rat glioma model at 11 and 15 days postimplantation.

RESULTS

In stage I, Gd-DTPA caused rapid and greatest tumor enhancement with a significant washout from the tumor during the 120-min experiment. Tumor enhancement using polylysine-(Gd-DTPA) occurred later and was significantly less compared to Gd-DTPA. Tumor signal intensity increased only slowly over time and the peak level of enhancement was least using albumin-(Gd-DTPA). In stage II, the mean (+/- 1 SD) Ki values were 1.1 +/- .24 at 11 days, and 9.3 +/- .8 at 15 days postimplantation. These results correspond well with published data obtained by autoradiography.

CONCLUSION

We believe that the differential enhancement pattern using contrast agents of different molecular sizes reflects a differential permeability of the pathologic blood-brain barrier, and that our studies demonstrate the feasibility of using frequent sequential images and a graphical approach to Ki calculation to determine the blood-to-tissue transport coefficient using contrast-enhanced MR.

Immunohistochemical characterization of rat central and peripheral nerve tumors induced by ethylnitrosourea

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.

Intermediate filaments and anaplastic change of ENU-induced gliomass: immunohistochemical study with vimentin and astroprotein (GFAP)

To study the expression of two different subclasses of intermediate filaments in ethylnitrosourea-induced rat cerebral gliomas, the number of cells immunopositive for each subunit protein, vimentin and astroprotein (GFAP), was quantitatively analyzed. Vimentin is a subunit protein of non-specific intermediate filaments which appear transiently in immature glial cells, while astroprotein (GFAP) is a subunit protein of glial filaments, normally expressed in mature astrocytes. Although most normal astrocytes were negative for vimentin, many tumor cells showed weak to strong immunoreaction for vimentin. The expression of vimentin was more frequent and intense in anaplastic forms of gliomas than in benign forms. Accordingly, the vimentin/GFAP ratio [the number of vimentin-positive cells divided by the number of astroprotein (GFAP)-positive cells] was increased from 0.23 to 1.86, and from 0.26 to 1.85, respectively, as oligodendrogliomas and mixed gliomas become anaplastic. The present study demonstrated that the immunohistochemical study for those two subclasses of intermediate filaments can provide important informations on the cell biological nature of glial tumors.

Risk of astrocytic brain tumors associated with occupational chemical exposures. A case-referent study

A case-referent study was conducted on the risk of brain tumors among workers exposed to organic chemicals in petroleum refining and chemical manufacturing. Brain tumor cases in northern New Jersey, Philadelphia, and the Gulf Coast of Louisiana were identified from death certificates of a recent three-year period. The cases (N = 300) were white men aged greater than or equal to 30 years with a confirmed diagnosis of glioblastoma multiforme, astrocytoma, or a mixed glioma with astrocytic cells. The referents (N = 386) were white men who died from causes other than brain tumor, epilepsy, cerebrovascular disease, suicide, or homicide and were frequency-matched with the cases on age at death, year of death, and study area. Next-of-kin were interviewed for complete occupational histories. No statistically significantly elevated odds ratios (OR) were associated with employment in the chemical industry. The risk of astrocytic tumors was elevated among the subjects with production or maintenance jobs in petroleum refining (OR 1.7, 95% confidence interval 0.7-4.2); however, it decreased with duration employed. There were nonsignificant excess risks of astrocytic tumors among the men exposed to cutting fluids (OR 1.6) or organic solvents (OR 1.3), and also among the subjects exposed to lubricating oils (OR 1.4), organic solvents (OR 1.5), or cutting fluids (OR 1.8) for greater than or equal to 20 years.

Promoting effect of 12-O-tetradecanoylphorbol-13-acetate on neurogenic microtumors initiated by transplacental exposure to N-ethyl-N-nitrosourea

The promoting effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the occurrence of neurogenic microtumors in SD-JCL rats initiated transplacentally with N-ethyl-N-nitrosourea (ENU) was investigated. The treatment with TPA induced earlier occurrence of microtumors than as compared with the initiation alone. Thus, TPA has tumor-promoting activity on the formation of neurogenic microtumors in rats prenatally exposed to ENU.

Morphological maturation of tumor cells induced by ethylnitrosourea (ENU) in rat brains. II. On the tumors by administration of ENU in the mid-gestational stage

In order to clarify the relationship between cellular characteristics of rat brain tumors and the administration time of chemical carcinogens, the incidence and morphology of microtumors in the offspring of five pregnant Sprague-Dawley rats injected with ethylnitrosourea (ENU) intraperitoneally on the 11th day of gestation (Group I) were compared with those of six pregnant rats injected with ENU on the 18th day of gestation (Group II). Twenty-four microtumors and 6 macrotumors were obtained in Group I and 58 microtumors and 5 macrotumors in Group II. Histologically, the macrotumors of Group I showed a poorly differentiated pattern which corresponded to primitive spongioblastomas in comparison with those of Group II which resembled human mature oligodendrogliomas, astrocytomas or mixed gliomas. The constituent cells of the microtumors of both groups were immature and were morphologically similar to each other. Immunohistochemically, the cells of microtumors of both groups were negative for Leu 7 and glial fibrillary acidic protein. Microtumors in Group I showed more infiltrative proliferation than those in Group II and had indistinct borders. The 3H-thymidine labeling index of the constituent cells of Group I was significantly higher than that of Group II (p less than 0.001). This study revealed that the constituent cells of microtumors of Group I, in spite of being morphologically similar with those of Group II, possess a greater growth potency than the latter. This difference in growth potency is responsible for the difference in the histological maturity of the macrotumors in each group. The difference in morphological maturation of enlarged gliomas induced by ENU appears to depend on the imperceptible difference of the target cell maturation at the initiation of oncogenesis.

Morphological maturation of tumor cells induced by ethylnitrosourea (ENU) in rat brains. I. On the tumors by administration of ENU in the late gestational stage

Sequential changes in the development of ethylnitrosourea (ENU)-induced rat brain tumors were examined histologically, immunohistochemically, electron microscopically and autoradiographically. In 47 Sprague-Dawley rats transplacentally administered ENU, 95 brain tumors developed, including 76 microtumors less than 1mm in diameter. Microtumors were found mainly in the paraventricular area, but some were found in the peripheral brain tissue. They were composed of small tumor cells which had round dark nuclei and scanty cytoplasm immunohistochemically negative for Leu 7 and glial fibrillary acidic protein (GFAP). The 19 macrotumors were mature gliomas, 3 of which histologically corresponded to oligodendrogliomas and 16 to mixed gliomas. The tumor cells of the former had small round nuclei with distinct perinuclear halos and a small amount of cytoplasm positive for Leu 7. The latter were chiefly composed of polygonal cells having large round nuclei and rich cytoplasm positive for GFAP. An autoradiographic study using 3H-thymidine revealed that the labeling index of the tumor cells was high in mixed gliomas and microtumors, but low in oligodendrogliomas. It may be concluded that the constituent cells of microtumors correspond to glioblasts or migrating neuroglias, which gradually mature to form oligodendrogliomas or astrocytomas.

Immunohistochemical studies on cellular character of microtumors induced by ethylnitrosourea in the rat brain utilizing anti-Leu 7 and anti-glial fibrillary acidic protein antibodies

To clarify the chronologic changes in the cellular morphology of ENU-induced rat brain tumors, microtumors in the early stage were examined immunohistochemically in comparison with macrotumors in the advanced stage. The tumor cells composing microtumors were negative for glial fibrillary acidic protein (GFAP), a specific marker of astrocytic cells, and Leu 7, a marker of oligodendrocytes, while cells of macrotumors were positive for either GFAP or Leu 7, showing characteristics of mature glial cells. The results suggested that the small round cells in the early developmental stage, generally thought to resemble mature oligodendrocytes, are not differentiated oligodendrocytes or astrocytes.

An improved rat brain-tumor model

The widely used intracerebral tumor implantation method by freehand injection into parietal or hippocampal areas of the rat brain has proven inadequate for reliable experimental therapeutic studies. Problems include poor intracerebral growth yields and significant rates of spread to extracranial tissues, lungs, and spinal cord. Major variables have been examined experimentally on a model using nitrosourea-induced nervous system tumor cell lines in sygeneic rats. A rapid stereotaxic method greatly improved the consistency of tumor placement. The optimal site was found to be the caudate nucleus. The production of a spheroid intracerebral growth was further facilitated by the use of 1% agar in the cell suspension medium and by an injection volume of 10 mu1 containing at least 10(4) cells. Further improvements involved injection technique and flushing of the operative field. These modifications have resulted in a 99% to 100% yield of intracerebral growth, with a marked reduction in the number and size of extracranial extensions and with distant metastasis rates of 0% to 5%. These results have continually improved with further experience. The method is satisfactory for radiation and chemotherapeutic trials in which survival time as an index of tumor size may be used an an end point.

Carcinogenicity of nitrosotrialkylureas in Fischer 344 rats

Three nitrosotrialkylureas were administered to female F344 rats as approximately 1-mM solutions in drinking water. Nitrosotrimethylurea, given for 47 weeks, gave rise to astrocytomas of the brain and tumors of the forestomach; nitrosotriethylurea induced a high incidence of adenocarcinomas of the breast and uterus and tumors of the forestomach. Nitrosomethyldiethylurea induced almost exclusively a high incidence of both astrocytomas of the brain and tumors of the spinal cord.

LDH isozyme analyses of ethylnitrosourea-induced central nervous system tumors in rats

To provide the significance of LDH isozymes in rat CNS tumors, the changes in lactic dehydrogenase isozyme and calculated ratios of H- to M- subunit were studied by means of polyacrylamide gel enzymoelectrophoresis in tumor extracts from CNS tumors (7 astrocytomas, 4 oligodendrogliomas, 7 mixed gliomas, 6 anaplastic gliomas, 3 glioependymomas, 1 astroblastoma, 11 neurinomas, 8 anaplastic neurinomas and 1 meningioma in Wistar rats which were induced by ethylnitrosourea). The isozyme patterns were compared to those obtained from normal rat CNS tissues. Among the glioma group, oligodendroglioma showed the highest H/M ratio followed by mixed glioma, glioependymoma, astrocytoma, astroblastoma and anaplastic glioma in order of decreasing of H/M ratios. On the other hand, the H/M ratio of neurinoma was significantly higher than that of anaplastic neurinoma. These observation suggested that determination of LDH isozyme patterns could supplement the histological evaluation of brain tumors.

N-ethyl-N-nitrosourea-induced spinal tumors in an inbred strain of W albino rats

Exposure to N-ethyl-N-nitrosourea (ENU) either transplacentally via the maternal bloodstream or postnatally by direct injection into the cerebellum or the cisterna magna resulted in a high incidence of spinal tumors in an inbred strain of W albino rats. After prenatal exposure to 60 mg ENU/kg maternal body weight, as many as 92% of the offspring developed 1 or more tumors in the spinal cord, whereas after postnatal exposure to 0.2 mg ENU/animal, 50% of the animals eventually developed spinal tumors. These tumors included relatively pure oligodendrogllomas, astrocytomas, and the usual mixed gllomas. Obvious clinical symptoms of paralysis of the limbs and weight loss accompanying the high incidence of tumors in the spinal cord make this system pertinent to the study of carcinogenesis in the central nervous system as well as to the study of related problems to the incidence of these tumors are discussed.

Tumor specific fluorescent and complement-dependent cytotoxic antibodies in the serum of rats with chemically induced brain gliomas

Brain tumors were induced in Sprague-Dawley and Long-Evans rats by administration of N-methyl-N-nitrosourea in the drinking water. Of these tumors, a grade 2 mixed glioma, a grade 2 to 3 astrocytoma and a grade 1 to 2 oligodendroglioma were established in vitro, maintained in culture and designated 75SD-G-376, 75SD-G-420 and 77LE-G-180, respectively. Of these mass cultures, two were successfully cloned and are currently available as 75SD-G-376C and 75SD-G-420C cell lines. Clonal lines produce S-100 protein and grow as tumors when isografted in young rats. Using the cultured cells as target cells , specific antibodies were searched for in the sera of the rats with the primary tumors by means of an indirect fluorescent antibody staining method and a complement-dependent antibody-mediated microcytotoxicity assay. Fluorescent and cytotoxic antibodies were demonstrated in the sera of the mixed glioma- and astrocytoma-bearing animals. However, a variable proportion of cells of the 75SD-G-376 and 75SD-G-420 lines showed no reaction with the corresponding sera. Furthermore, cytotoxic antibodies had a lytic effect on the autologous glioma cells only in the presence of rabbit complement.

[Cytophotometric determination of DNA concentration in the cells of experimental brain tumors. II. Primary tumors of rat cerebellum induced by 9, 10-dimethyl-1, 2-benzanthracene]

The Feulgen-DNA cytophotometry was applied for studies of 31 rat cerebellum tumors induced by 9, 10-dimetyl-1,2-bensantracene. Most of these gliomas (22) were astrocytomas of different grades of malignancy. The histological diagnosis of other tumors was: glioblastoma -- 4, oligoastrocytoma -- 2, oligodendroglioma -- 1, gliosarcoma 1. The majority cells of 26 tumors had diploid or paradiploid DNA quantity, 4 tumors (1 astrocytoma, 3 dedifferentiated astroyctomas) had triploid modal classes. The tetraploid modal class and a large number of polyploid cells were found only once for glioblastoma multiforme. A supposition was made that drastic changes of ploidy could arise for the second time during the process of tumor evolution. The authors failed to show any exact differences in the ploidy of gliomas in rats with athyreosis or hyperthyreosis, and in the ploidy of somatic cells in control animals.

Inhibitory effect of sodium ascorbate on ethylurea and sodium nitrite carcinogensis and negative findings in progeny after intestinal inoculation of precursors into pregnant hamsters

To assess their carcinogenic effects, the ethylnitrosourea (ENU) precursors, ethylurea and sodium nitrite, [were administered to pregnant hamsters as a single intragastic] dose on day 15 of gestation, or introduced into the cecum on day 14. Since sodium ascorbate (NaASC) inhibits the biosynthesis of nitrosamides, identical doses of the precursors were given concomitantly with NaASC. Progeny of mothers treater intragastrically developed significant incidences of neurogenic tumors of the peripheral nervous system, with a predominance in females. The concurrent administration of NaASC with ENU precursors prevented carcinogenic effects in the progency, whereas the simultaneous inoculation of the precursors into the cecum produced no carcinogenic effects in the offspring.

[Deoxyribonucleases in spontaneous and experimental tumors of the nervous system]

DNA- and RNA-concentrations, as well as in vitro activities of DNase I (EC 3.1.4.5), DNase II (EC 3.1.4.6), and DNase I inhibitor, have been determined in 63 spontaneous (man) and 22 experimentally induced (rat) nervous system blastomas of various types and of different degrees of malignancy. Generally, a distinct elevation of DNA concentrations and of the ratio (Q) of DNase II- to DNase I-activities has been observed when compared with control values. A statistically significant relationship could be demonstrated between increase of DNA concentrations and Q in experimentally induced neurinomas of rats as well as in human astrocytomas and glioblastomas. Whereas the increase of Q may be a biochemical expression of elevated DNA synthesis of tumour cells, no conclusions can be drawn as to the role of DNases in the process of malignant transformation.

Transplacental induction of neurogenic tumors in BD IX rats by intragastric administration of ethylnitrosourea precursors

The concurrent daily intragastric administration of ethylurea at two dose levels (50 mg/kg and 100 mg/kg bodyweight) together with one dose level of sodium nitrite (50 mg/kg bodyweight) by a stomach tube to pregnant BD IX rats from day 15 to day 22 of gestation resulted in the induction of neurogenic tumors in all offspring. Since both ENU-precursors alone do not produce neurogenic tumors, these results are evidence of ENU formation from its precursors under the influence of gastric juice. Differences in the survival time and the incidence of tumors at both dose levels were not significant. The amount of ethylnitrosourea synthesized in the animals was very close at both dose levels, and was dependent on the amount of sodium nitrite applied. The experimental results are consistent with the conclusion, that the rat fetuses had been exposed to a total amount of about 60 mg/kg ethylnitrosourea. Neurogenic tumors dominated with 98% incidence over the non-neurogenic. The incidence of neurogenic tumors per rat was high (6.0 for Group I and 6.7 for Group II). Neurogenic tumors were equally distributed among the central and peripheral nervous systems. The neurogenic tumors induced with the precursors of ethylnitrosourea were morphologically similar in all aspects to those induced with the carcinogen itself and could be classified as oligodendroglioma, astrocytoma, mixed glioma, anaplastic glioma, glioependymoma, ependymoma, and neurinoma. Three unusual tumors were found: one early anaplastic "septum ependymoma" in the dorsal column of the spinal cord, and two special mixed tumors of the cranial nerves, i.e. a neurinoma with portions of an oligodendroglioma and a neurinoma with parts of an invasive ependymoma.

Histopathological studies of the nervous system tumors in rats induced by N-nitroso-methyl-urea

Histopathological examinations were made on tumors of the nervous system induced in rats of Donryu strain by weekly intravenous injections with N-nitroso-methyl-urea (NMU) or by a single administration of NMU through the mothers. A total of 176 neural and nonneural neoplasms were produced in this study. It was suggested that the fetal nervous system of Donryu rats was also highly susceptible to the oncogenic effects of NMU. Of these tumors produced, those of the peripheral nervous system amounted to 121, comprising 68.7% of the total number of the neoplasm. Microscopically, most of the nerve tumors showed the histology corresponding to that of human neurinomas. Many tumors, however, disclosed more or less anaplastic cytological appearance. Fifteen gliomas were produced in the brain and spinal cord. Microscopically, they were classified into mixed glioma, oligondendroglioma and anaplastic astrocytoma. The commonest brain tumors produced in rats from intravenously treated group were periventricular mixed gliomas, while gliomas in rats from transplacentably treated group showed an isomorphic histology with a close resemblance to that of oligodendroglioma.