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

Nonimmunological defenses are very diverse in type. Some are directed against already transformed cells and belong to mechanisms of containment. Others exert a surveillance by preventing or inhibiting initial events of carcinogenesis. Chalones and oncolytic factors in sera and exudates are agents of containment. Under appropriate circumstances, the autoxidation of thiols and the formation of mixed disulfides lead to destruction of tumor cells in vitro and in vivo. Both processes involve the generation of superoxide radicals and of hydrogen peroxide which, in turn, activate the peroxide:peroxidase:halide system. Thiol:disulfide ratios and interchange codetermine the antioxidative activity of cellular membranes, thus bearing on carcinogenesis. Many aliphatic and aromatic antioxidants are endowed with anticarcinogenic properties. The fact that they are inhibitors of free radical processes corroborates the increasingly evident role of free radicals in carcinogenesis. Endogenous antioxidants and exogenous ones in foods are agents of surveillance. Antioxidant activity, linked with the ergastoplasm, points to a homeostatic mechanism that prevents self-accelerating chain reactions from leading to membrane damage or to carcinogenesis. Carcinogens can also be inactiviated by microsomal enzymes belonging to an overall mechanism of detoxification. Activity levels of these systems depend on diet and state of nutrition. They may be naturally very low, but they can be increased with various inducers.
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PMID:Nonimmunological host defenses: a review. 17 22

It was previously reported that the properties of alcohol dehydrogenase of a rat hepatocellular carcinoma (Becker H-252), a tumor of intermediate growth rate, were different from those of the liver enzyme, suggesting different isozymes. To determine whether the degree of differentiation affected the isozyme of alcohol dehydrogenase, a fast-growing, poorly differentiated tumor and one that is well differentiated and of intermediate growth rate were studied. Alcohol dehydrogenase from Morris hepatoma 7288ctc, a fast-growing, poorly differentiated tumor, had properties similar to those found with the Becker-H-252 tumor, including a high Km for ethanol and acetaldehyde and the absence of substrate inhibition. By contrast, alcohol dehydrogenase from the well-differentiated Morris hepatoma 5123C had properties similar to those of the liver enzyme. Thus, alcohol dehydrogenase is another example of an enzyme the isozyme composition of which changes with neoplastic de-differentiation. Further studies, including gel electrophoresis, substrate specificity patterns, and interaction with antibodies to alcohol dehydrogenase, are required to determine the factors responsible for the biochemical defect that occurs at the molecular level during carcinogenesis and whether the alcohol dehydrogenase isozymes in the Becker H-252 and Morris 7288ctc hepatomas are identical. A survey of several normal rat tissues revealed that only the stomach contains this unique isozyme of alcohol dehydrogenase.
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PMID:Kinetic properties of alcohol dehydrogenase in hepatocellular carcinoma and normal tissues of rat. 17

Biochemical data provide good evidence of a lack of acid and alkaline RNase activities in ascites tumour cells. Analyses of whole solid tumours appear of doubtful value, but fractionation studies reveal RNase deficiencies in mitochondrial fractions whereas inconsistent results are reported for microsomal fractions. Nuclei, nucleoli, and ribosomes isolated from tumours show relatively weak activities. Large variations are noted in determinations on purified lysosomes. Histochemical analyses by two different approaches demonstrate a multifocal loss of RNase activities in preneoplastic tissues, a lack of activities in cancer cells, and the presence of appreciable activities in stromal tissue and necrotic areas of tumours. These results suggest that RNase activities found in homogenates and cellular fractions of heterogeneous tumours may derive mainly from stromal cells, phagocytes, and extracellular fluids of necrotic areas. A close correlation seems to exist between activation of RNases and tumour regression. A large variety of therapeutic agents induce increases in tumour RNase activities whereas ineffective agents do not. The activation of RNases precedes obvious regression and apparently represents de novo synthesis of RNases in cancer cells. It emerges from these studies that loss of RNase activities could represent a critical event in carcinogenesis, that RNase deficiencies would persist in cancer cells, and that RNase activation would be closely associated with tumour regression. Losses of RNase activities in preneoplastic tissues are followed by changes in the properties of cytoplasmic RNA probably due to alterations in ribosomes in areas of neoplastic transformation. Deficiencies in the RNase system could be the source of abnormalities in cellular RNA or RNA-containing particles that would lead to neoplasia.
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PMID:Ribonucleases and neoplasia. 18 16

1. At least one third of all children with Wilms' tumors have evidence of aberrant metanephric differentiation, hamartomas, adenomas and nodules of blastema or Wilms' tumorlets in the subcapsular renal cortex. Only the presence of nodular renal blastema was found to correlate with younger age, suggesting that the other tumorlike lesions may be derivatives. 2. In our experience, all patients with bilateral and sequential bilateral Wilms' tumors have exhibited these characteristics in the "uninvolved" renal tissue removed at nephrectomy. 3. Pancortical (infantile), diffuse superficial (late infantile) and multifocal (juvenile) variants of nephroblastomatosis are defined. In the latter 2 forms of nephroblastomatosis the prognosis after modern therapy is at least as good as it is in patients with unilateral, unicentric Wilms' tumor arising in a histologically normal kidney. 4. The morphologic evidence presented strongly indicates that Wilms' tumor in patients with nephroblastomatosis develops either from nodular blastema or metanephric hamartomas. It is hypothetically possible that all Wilms' tumors develop from these precursors. The latent period between cessation of nephrogenesis and clinical presentation of Wilms' tumor is interpreted as favoring the hypothesis that carcinogenesis per se is the result of a postnatal event but that the substrate for tumor development, aberrant metanephric proliferation, has its inception during gestation.
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PMID:The nephroblastomatosis complex and its relationship to Wilms' tumor: a clinicopathologic treatise. 18 29

The blocking of specific SV40-induced resistance of hamsters by the sera collected from 12 individual hamsters infected with SV40 when newborn was studied at different periods of primary virus-induced carcinogenesis. The serum samples were collected at the following periods of primary carcinogenesis: during the latent period (60 days after virus inoculation), at the day of primary tumor appearance, and 19-36 and 45-57 days after primary tumor appearance. For detection of the blocking activity of the collected sera the cells of transplantable SV40 test-tumor were pretreated in vitro with these sera and with control normal hamster sera, and then used for challenge in vivo in SV40-immunized and normal hamsters. With the use of such method, as a rule, no blocking activity of the serum samples collected at any time after the tumor appearance was observed. However, the sera obtained from 7 out of 12 of these hamsters during the latent period significantly decreased the resistance index of animals challenged in transplantation test with the serum pretreated tumor cells. Possible explanations of these findings are discussed.
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PMID:In vivo blocking of SV40 virus-induced antitumor resistance by Syrian hamster sera from early stages of primary SV40 carcinogenesis. 18 66

Lifetime tests were done in NZR inbred rats of dimethylnitramine (DMNO) by addition to the drinking water (average dose 1.83 g/kg body weight) and in NZO mice by repeated subcutaneous injection from birth to 7 months of age followed by administration in drinking water (total average dose 4.72 g/kg body weight). Rats developed hepatocellular carcinomas (85%), some of which metastasized. Mice developed hepatocellular carcinomas (81%) and renal adenocarcinomas (48%). Statistically significant increases of other tumor types also occurred in mice. The main targets for DMNO carcinogenesis appeared to be the liver cell epithelium and, at higher dose rates, renal tubular epithelium.
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PMID:Carcinogenicity of dimethylnitramine in NZR rats in NZO mice. 18 4

The central theme of this communication is the recognition of an immunodiagnostic potential in a herpes virus antigen, the molecular interrelationship of which with cervical tumor cells is described. In addition to the productive infection caused by herpes simplex virus type 2 (HSV-2) we are confronted by latency and, as suggested by recent studies, by cancer. These different types of virus-host cell interactions are discussed at the host, as well as at the cellular level. A defined level of molecular interaction between host and viral gene products must exist if the virus is to co-exist with the host, as is the case in latency and carcinogenesis. The molecular interpretations posit the presence, in the squamous cervical tumor cells, of a product of the expression of the viral genome that has immunodiagnostic potential. The antigen designated AG-4 fulfills these predictions and appears to have immunodiagnostic potential. AG-4 is present in cervical tumor biopsies, but not in normal cervical tissue. It is a structural component of the HSV-2 virion that, in tissue cultures infected with HSV-2, is synthesized preferentially under conditions that prevent the normal replication of the virus. In view of its structural nature it is most probably virus-coded. AG-4 antibody identified in complement fixation assays with antigen prepared in tissue culture, disappears following successful tumor removal and reappears during cancer recurrence. This antibody also potentially identifies those patients with cervical atypia that are at high risk of neoplastic progression. The clinical benefits of the assay are evident.
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PMID:Immunodiagnostic potential of a virus-coded, tumor-associated antigen (AG-4) in cervical cancer. 19 36

All Caucasian women in a large Eastern city who developed pathologically confirmed cervical cancer between 1950 and 1969 are being prospectively followed in an epidemiological test of the venereal hypothesis of cervical carcinogenesis. We are attempting to identify all men who were married to these probands at any time prior to the date of their cancer diagnosis. The ultimate objective is the identification of all the other wives of the proband husbands in order that their risk of cervical cancer be assessed. A random sample of control wives similar to the other wives in age, race, date and place of marriage as well as prior marital status is also being followed. To date, a total of 1,087 other wives and 659 control wives has been fully traced. Cervical cancer or carcinoma in situ was detected in 29 (2.7%) of the other wives and in seven (1.1%) of the control wives. A total of 14.0% of the other wives had either cervical cancer or a cervical cytological specimen which was other than normal. The corresponding statistic for the control wives was 8.0%. These differences in the prevalence of cervical cancer and of non-normal cervical cytology are statistically significant. In the course of this investigation so far, we have identified 29 "marital clusters" of cervical cancer in which two women married to the same man have all developed cervical neoplasms. The observed number of 29 clusters may be compared with an expected number of 11.6. This investigation, as yet incomplete, offers confirmatory evidence of the possible role of venereal factors in the pathogenesis of human cervical neoplasia. While the genital herpesvirus is the likeliest candidate, other venereal elements might also be involved.
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PMID:Venereal factors in human cervical cancer: evidence from marital clusters. 19 39

Electron microscopic observations of sequential stages of skin carcinogenesis induced by tobacco smoke condensate (SC) and a cyclohexane fraction of tobacco smoke condensate (G) revealed an increase in incidence of intracisternal A particles within the epidermal cells. Tumours induced by SC also contained C-type particles, but these were not seen in G-induced tumours or after irritant or solvent treatment. There was no evidence of an increase in intracisternal A particles after irritant or solvent treatment. A direct relationship between the proliferation of A particles and neoplastic growth of BALB/c mouse epidermis appears likely. The data suggest possible activation of a latent C-type virus by SC.
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PMID:C-type and intracisternal A-type virus particles during epidermal carcinogenesis by tobacco smoke condensate in BALB/c mice. 19 15

The etiology of cancer resembles that of many other diseases in that multiple factors may be required. Because of this, the role or viruses in the etiology of human cancers is especially difficult to assess. When animal tumor systems were used as models, the roles of various predisposing characteristics in virus oncogenesis were elucidated. Extrapolation of these findings to the human diseases suggests the importance of genetics, age, hormones, immune competence, and stress in determining susceptibility to tumor development in individuals infected with an oncogenic virus. The importance of cofactors in induction of those human tumors most strongly associated with virus infection, including Burkitt's lymphoma, nasopharyngeal carcinoma, cerviccal carcinoma, acute myelogenous leukemia, and breast cancer, is reviewed. Understanding of the role of these cofactors in virus carcinogenesis may lead to disease prevention through elimination of one or more of the cofactors.
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PMID:The viral etiology of cancer: a realistic approach. 19 10


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