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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The frequent failure of the host's immunologic responses to impose restraints on tumor growth and dissemination has led to the realization that a number of factors, both immunologic and nonimmunologic, may act in concert to affect tumorigenesis. Immunologic mechanisms involved in tumor cell destruction are predicated principally on in vitro procedures, but the relevancy of these experimental observations to the actual events in vivo remains unclear and unresolved. The macrophage has been shown to be an integral segment of the immune response and to constitute an important element of the host defense against tumors. In this connection, interferon may be implicated in tumor cell destruction through macrophage activation to cytotoxicity. Studies of age-related susceptibility of New Zealand Black mice to three different carcinogens, ie, 3-methylcholanthrene, x-irradiation, and murine leukemia virus, have further emphasized the multifactorial determinants which may be operational in oncogenesis. Advances in our knowledge of tumor immunology have suggested a number of possible modalities for preventing tumors from escaping immunologic destruction and should continue to contribute to further elucidation of neoplastic mechanisms.
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PMID:Tumor immunity. An overview. 71 38

To study the long term effects of estrogen administration in mice, virgin female C3H/HeJ mice are being fed diets containing 0, 10, 100 or 500 ppb of diethylstilbestrol (DES) or 0, 100, 1000, or 5000 pph of 17beta-estradiol (E2) from 6 to 110 weeks of age. C3HeB/FeJ mice are being fed diets containing 08 10, 100, or 500 ppb DES FROM 6 TO 136 WEEKS OF AGE. Pathologic studies were conducted on 396 such mice sacrificed at 52 weeks and on over 500 others sacrificed at various intervals. After 52 weeks on 500 ppb DES or 5000 ppb E2, the cervix of both populations often showed stromal mucoid changes and adenosis characterized by focal replacement of squamous by columnar epithelium lining the cervical canal assoicated with glandular downgrowths into the subjacent stroma. The uterine horns showed hyperplastic glands, which often penetrated the muscularis, and focal endometrial and perivascular hyalin deposits. The ovaries showed atrophy with absence of corpora lutea. Ceroid deposits were increased in the ovaries and adrenals. Sternal bony trabeculae were increased. The incidence of uterine cervical adenosis and of mammary hyperplastic alveolar nodules and tumors (mainly type B, Dunn's classification), was higher in C3H/HeJ than in C3HeB/FeJ mice. Mice on lower doses of DES or E2 had less frequent and severe similar changes. Tumors observed to date only in estrogen-treated mice included 4 endometrial adenocarcinomas and an adenoacanthoma of a uterine horn, 14 cervical adenocarcinomas often appearing to arise from areas of adenosis, a vaginal squamous cell carcinoma, a cervical granular cell myoblastoma, 1 sternal and 3 cranial osteosarcomas, and a mesothelioma. The majority of the malignancies occurred in C3H/HeJ mice. These findings indicate that the mammary tumor virus factor facilitates DES-induced mammary tumorigenesis in C3H mice and may contribute to other DES-induced malignant and premalignant lesions.
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PMID:Pathological changes in female C3H mice continuously fed diets containing diethylstilbestrol or 17beta--estradiol. 72 80

The case of a secreting adrenal tumor in a seven month old hemihypertrophic girl is described. Some features of hemihypertrophy and its relationships with the E.M.G. Syndrome and abdominal tumors are commented upon. The reported case is a typical association of malformation with tumor and recalls the close relationship between teratogenesis and oncogenesis.
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PMID:[Hemihypertrophy and functioning adrenal tumor (author's transl)]. 74 75

Marek's disease (MD) is a highly infectious neoplastic condition of chickens caused by a herpesvirus. The virus is cell associated in tumors and in all organs except in the feather follicle where enveloped infectious virions egress from the body. From this source, infection is spread horizontally by the airborne route to the environment and to other chickens. Vertical transmission from dam to offspring does not occur or at best is very rare. The nonpathogenic herpesvirus of turkeys (HTV) is ubiquitous in turkeys and is probably spread horizontally by the airborne route. When chickens are inoculated with this virus, they do not subsequently develop MD even after infection with virulent Marek's disease virus. The Marek's disease virus, not the HVT, will spread horizontally from dually infected birds. The HVT vaccine is safe and highly effective in preventing MD under field conditions, and most chickens throughout the world are vaccinated with this vaccine. Other vaccines that have been used but have disadvantages over HVT include the following: (a) the highly pathogenic HPRS 16 strain of Marek's disease virus was attenuated by passage in cell culture. The attenuated virus protects against MD and does not spread, but "over-attenuated" virus does not protect; (b) naturally apathogenic strains virologically, immunologically, and epizootiologically similar to pathogenic strains will protect when adminstered before infection with the virulent strains; (c) virus preparations that have been chemically treated to inactivate infectivity protect only slightly. When a candidate vaccine virus for the prevention of herpesvirus-induced cancer in humans is developed, the purity of the vaccine preparations will be easily determined by modern techniques. However, measurements of safety and effectiveness are a significant problem. If, analogous to the MD model, the vaccine will have to be administered shortly after birth and the incubation period to development of neoplasms is long, then pathogenicity tests in nonhuman primates and other animals may be of limited valued. However, biochemical demonstration that the segment of the nucleic acid responsible for oncogenesis is absent from the vaccine virus may be the major indication that the vaccine is nonocogenic and therefore safe. Because of the low incidence of neoplasia and long incubation period, the effectiveness of the vaccine will be difficult to test. The vaccine possibly will protect against an acute manifestation of viral infection. Future research on MD will be directed to determining the mechanism of protection against disease, i.e., whether immunity is mediated by thymus- or bursa-dependent systems, and to identifying the protective antigen, i.e., which cell surface or an interior antigen induces the protective immunity. The prevention of MD by vaccination may become a very fruitful area for model studies on prevention of human cancer by vaccination.
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PMID:Prevention of Marek's disease: a review. 76 59

The effect of ethionine on pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide (4-HAQO) in rats was studied. The high incidence of hyperplastic nodules developed in the exocrine pancreas of animals receiving a single injection of 4-HAQO only or protein-deficient diet containing 0.5% ethionine for 4 days followed by 4-HAQO. The incidence of adenoma was higher than that of hyperplastic nodules and well-differentiated adenocarcinoma developed in 1 out of 12 animals receiving protein-deficient diet containing ethionine for 18 days followed by 4-HAQO. No tumor was found in the pancreas of animals that received 0.005N HCl without 4-HAQO. These results suggest that the pancreatic tumorigenesis of 4-HAQO is enhanced by ethionine.
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PMID:Enhancement of pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide by ethionine in rats. 81 56

Analysis of literary data and the author's findings have shown that the transplacental action of most of the compounds tested in experiments on rats manifested itself by a neurotropic carcinogenic effect. A marked neurotropism in transplacental carcinogenesis in rats is characteristic even for such drugs (e.g. dimethylbenzathracene) that have never induced neurogenic neoplasms in adult animals. To elucidate the relationship between teratogenesis and carcinogenesis the peculiarities of tumor development in brain against the background of malformations induced by combined transplacental treatment by methylnitrosourea (MNU) and ethylnitrosourea (ENU) in rats have been studied. Tumorigenesis was sharply inhibited by administration of ENU (on the 13th day) prior to MNU treatment (on the 15th day). There is reason to believe that the cytotoxic effect of MNU for microephaly results in the death of a considerable part of the cell population already transformed by ENU. In a special series of experiments characteristics of the permeability of polycyclic aromatic hydrocarbons through the placenta in rats have been specified.
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PMID:Some results and prospects of transplacental carcinogenesis studies. 82 60

The effect of oral administration of coumarin on the induction of breast tumors brought about by DMBA has been studied in female Wistar rats. Coumarin given before DMBA caused a significant dose-related suppression of the incidence of adenocarcinomas, although no histologic difference was found in the tumor between untreated and coumarin-treated rats. The growth rate, size and multiplicity were also reduced and tumor occurrence was delayed. Parallel with the suppression, hepatic drug metabolizing activity was decreased and serum prolactin level increased. Coumarin given after DMBA elicited no effect on the carcinogenic potency of DMBA. In contrast to the action on mammary tumorigenesis, coumarin provided no protection against hemopoietic and adrenocortical necrosis brought about by DMBA.
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PMID:Suppression of 7,12-dimethylbenz(alpha) anthracene-induced breast carcinoma by coumarin in the rat. 82 91

Lines of chickens selected from a common ancestral population for either resistance or susceptibility to Marek's disease developed contrasting frequencies of particular B alloalleles. Comparison of inoculated sibs in backcross-families revealed that the B alloalleles characterizing the two lines accounted for an eightfold difference in tumor incidence. This genetic difference in tumorigenesis associated with the alloalleles of the major histocompatibility complex is probably expressed through the cell-mediated immune system.
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PMID:Marek's disease: effects of B histocompatibility alloalleles in resistant and susceptible chicken lines. 83 Dec 69

It is immature elements of both proliferating and nonproliferating tissues that serve target cells in oncogenesis. Fould's concept of the independant development of tumor characters is supplemented with the idea that one must discriminate between fundamental festures, common for both benign and malignant neoplasms (uncontrolled growth), and secondary ones manifesting malignancy. Some of the latter are thought to be obligatory (invasiveness with destructive growth and the systemic effect) and others--facultative (capacity of metestasizing, cataplasia, etc).
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PMID:[Origin of embryonal features of the neoplasm and tumor progression]. 84 33

Effect of dietary indole on the urinary bladder tumorigenesis by chronic dibutylnitrosamine (DBN) treatment was evaluated in hamsters. In the first experiment, in which DBN-water and diet were given ad libitum, dietary indole significantly suppressed bladder tumor incidence. The inhibitory effect was more pronounced in males. In the second experiment, in which consumption of both diet and DBN-water was rigidly controlled by pair-feeding, dietary indole again significantly suppressed bladder tumor incidence; its effect was similar in both males and females. This suppressive effect of indole on bladder tumorigenesis contrasted markedly with its failure to suppress tumors at other sites such as nasal sinuses, trachea, esophagus, and fore-stomach.
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PMID:Suppression of dibutylnitrosamine-induced bladder carcinomas in hamsters by dietary indole. 86 59


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