Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two enzymes that catalyze the hydrolysis of l-asparagine have been isolated from extracts of Pseudomonas geniculata. After initial salt fractionation, the enzymes were separated by chromatography on diethylaminoethyl-Sephadex and purified to homogeneity by gel filtration, ion-exchange chromatography, and preparative polyacrylamide electrophoresis. The enzymes differ markedly in physicochemical properties. One enzyme, termed asparaginase A, has a molecular weight of approximately 96,000 whereas the other, termed asparaginase AG, has a molecular weight of approximately 135,000. Both enzymes are tetrameric. The asparaginase A shows activity only with l-asparagine as substrate, whereas the asparaginase AG hydrolyzes l-asparagine and l-glutamine at approximately equal rates and it is also active with d-asparagine and d-glutamine as substrates. The asparaginase A was found to be devoid of antitumor activity in mice, whereas the asparaginase AG was effective in increasing the mean survival times of both C3H mice carrying the asparagine-requiring Gardner 6C3HED tumor line and Swiss mice bearing the glutamine-requiring Ehrlich ascites tumor line. These differences in antitumor activity were related to differences in the K(m) values for l-asparagine for the two enzymes. The asparaginase A has a K(m) value of 1 x 10(-3) M for this substrate whereas the corresponding value for the AG enzyme is 1.5 x 10(-5) M. Thus the concentration of asparagine necessary for maximal activity of the asparaginase A is very high compared with that of the normal plasma level of asparagine, which is approximately 50 muM.
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PMID:Tumor inhibitory and non-tumor inhibitory L-asparaginases from Pseudomonas geniculata. 3 47

The interaction of analogs of L-aspartic acid with adenylosuccinic acid synthetase, L-asparagine synthetase, and L-aspartic acid transcarbamylase is discussed. Each of these enzymes is of critical importance in the economy of certain types of tumor cells. L-Alanosine, a new antitumor antibiotic, is shown to be accepted as a substrate by the enzymes of de novo purine biosynthesis which ordinarily use L-aspartic acid as a substrate; as a consequence of this interaction, an anabolite is thought to be produced which impairs the formation of adenine nucleotides by inhibiting adenylosuccinate synthetase, leading to an interruption in DNA synthesis. Homoserine-beta-adenylate, guanidinosuccinic acid, and PA2LA [3-(phosphonacetylamido)-L-alanine] are shown to be inhibitors of L-asparagine synthetase from murine lymphoblasts; each of these analogs of L-aspartic acid exhibits novel structural properties which can be used by synthetic chemists in the design of molecules with an even greater ability to block the biosynthesis of L-asparagine. Certain aspects of the mechanism of action of PALA (N-phosphonacetyl-L-aspartic acid) were examined. This agent, which is a potent inhibitor of mammalian L-aspartic acid transcarbamylase, is capable of stimulating the homologous enzyme from Escherichia coli under certain circumstances. In vivo the duration of inhibition produced by this agent is shown to be unusually protracted; for example, L-aspartic acid transcarbamylase in mouse liver remains at 30% of treatment levels for greater than or equal to 20 days after a single therapeutic dose of PALA. This long-lasting effect reflects either sluggish synthesis of new enzyme molecules in this organ or shuttling of the inhibitor from old to new molecules. It is suggested that new and still more potent analogs of L-aspartic acid be sought, and that they be screened, inter alia, against these target enzymes.
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PMID:Analogs of L-aspartic acid in chemotherapy for cancer. 3 3

Proteases capable of activating procollagenase from gingiva and from fibroblast and macrophage monolayer cultures were harvested from homogenates of canine tumor mast cells. The mast cell proteases lysed casein and Azocoll but not native collagen. In low salt concentrations the enzymes existed at high molecular weight complexes, which were dissociated by increasing the salt concentration above 1.0 M (NaCl, KCl). Gel filtration in 1.4 M KCl separated the protease activity into three peaks, all of which activated procollagenase. Two of the enzymes showed substrate specificities (hydrolysis of p-tosyl-L-arginine methyl ester and benzoyl-tyrosine ethyl ester) and reactive center reactivities similar to pancreatic trypsin and chymotrypsin. Based on gel filtration, apparent molecular weights of 160 000 (p-tosyl-L-arginine methyl ester esterase), 90 000 (main procollagenase activator) and 36 000 benzoyl-tyrosine ethyl ester esterase) were determined. Activation of procollagenase resulted in a 18-20 000 decrease of the molecular weight. The activation was directly related to the amount of activator added within certain limits. Further addition of activator resulted in proteolytic inactivation of collagenase.
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PMID:Activation of fibroblast procollagenase by mast cell proteases. 5 9

The RNA-directed DNA polymerase of murine mammary tumor virus, a type B RNA tumor virus, was purified sequentially through DEAE-cellulose, phosphocellulose (step gradient), and phosphocellulose (linear salt gradient) chromatography followed by glycerol sedimentation centrifugation. During all stages of purification, coincident peaks of RNA-directed DNA polymerase activity, templated by polyribocytidylate-oligodeoxyguanidylate, and RNase H digestion of [3H]polyriboadenylate-polydeoxythymidylate were observed, and both enzymatic activities displayed a cation preference for magnesium. Under conditions that removed adventitiously associated nucleases, RNase H activity was found to co-purify with polymerase. The specificity of this nuclease was assayed with various prepared substrates, which indicated that the polymerase-associated RNase H activity was directed only against the RNA strand of an RNA-DNA hybrid. It is highly probable that RNase H (RNA-DNA hybrid: ribonucleotide-hydrolase, EC 3.1.4..34) and RNA-directed DNA polymerase of type B viruses are associated enzymatic activities analogous to those observed for avian and mammalian type C RNA tumor viruses.
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PMID:RNase H and RNA-directed DNA polymerase: associated enzymatic activities of murine mammary tumor virus. 6 21

The distribution of simian virus 40 (SV40)-specific proteins in nuclear subfractions of pulse-chase-labeled HeLa cells infected with nondefective adenovirus type 2 (Ad2)-SV40 hybrid viruses was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND5 specifically associate with the nuclear matrix and are virtually absent from the high-salt nuclear extract. In Ad2+ND4-infected HeLa cells, the SV40-specific proteins with molecular weights of 64,000 (64K) and lower also specifically associate with the nuclear matrix. The SV40-specific 72K, 74K, and 95K proteins were found both in the nuclear matrix and in the high-salt nuclear extract. Analyses of the nuclear matrices isolated from hybrid virus-infected cells by immunofluorescence microscopy showed that SV40 U-antigen-positive sera from SV40 tumor-bearing hamsters react with SV40-specific proteins integrated into nuclear matrices of HeLa cells infected by Ad2+ND1, Ad2+ND2, and Ad2+ND4, but not with nuclear matrices of HeLa cells infected by Ad2+ND5. This suggests that SV40-specific proteins of Ad2+ND1, Ad2+ND2, and Ad2+ND4 integrated into the nuclear matrix carry SV40 U-antigen determinants. The apparent discrepancy in the subcellular localization of SV40-specific proteins in hybrid virus-infected cells when analyzed by biochemical cell fractionation procedures and when analyzed by immunofluorescence staining is discussed.
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PMID:Simian virus 40 (SV40)-specific proteins associated with the nuclear matrix isolated from adenovirus type 2-SV40 hybrid virus-infected HeLa cells carry SV40 U-antigen determinants. 7 34

The nature and function of suppressor factor(s) elaborated by suppressor T cells in response to certain chemically induced tumors have been further defined. Thus, suppressor factor(s) specific for the S1509a methylchol-anthrene-induced fibrosarcoma have been shown to bear determinants encoded by the I-J subregion of the murine MHC since suppressive activity is removed by passage of the factor through an immunoadsorbent composed of anti-I-Jk coupled to Sepharose. No loss of activity was observed after passage of factor through control columns composed of normal mouse globulin. Furthermore, activity could be recovered from the relevant immunoadsorbent by elution with high salt. The administration of crude suppressor factor(s) to normal animals for 4 days resulted in the development of a population of suppressor cells that act in a manner analogous to the suppressor cell population used for production of factor. These factor-induced suppressor cells are T cells and exhibit an antigen specificity similar to that displayed by the tumor-induced suppressor cells. Thus, tumor-specific suppressor factor(s) bear I-J determinants and are capable of inducing the appearance of suppressor T cells in the nontumor-bearing host, which may then act in a specific manner to limit host responsiveness to tumor antigen.
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PMID:Regulation of the immune response to tumor antigen. IV. Tumor antigen-specific suppressor factor(s) bear I-J determinants and induce suppressor T cells in vivo. 8 78

The original metal-salt technique of Gomori (1948a) employing p-chloranilidophosphonic acid as a substrate for the demonstration of the activity of phosphoamidase has been used with varying success by a number of investigators for light microscopy. Cyclophosphamide (endoxan) which is a cytotoxic drug known to activate phosphoamidase and other lysosomal enzymes in neoplasm (Grillo, 1971) is proposed as another substrate for the enzyme for both light and electron microscopy.
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PMID:Light and electron histochemistry of phosphoamidase with p-chloranilidophosphonic acid and with cyclophosphamide (endoxan). 8 80

Simian virus 40 (SV40)-transformed cells and cells infected by the nondefective adenovirus 2(Ad2)-SV40 hybrid viruses Ad2+ND1 and Ad2+ND2 were analyzed for SV40 T- and U-antigens, respectively, using individual hamster SV40 tumor sera or serum for which U-antibodies were removd by absorption. These studies showed that (i) T- and U-antigens can be defined by separate classes of antigenic determinants and (ii) the U-antigenic determinants in SV40-transformed cells and in hybrid virus-infected cells are similar. The apparent discrepancy in the subcellular location of U-antigen in SV40-transformed cells (nuclear location) and in hybrid virus-infected cells (perinuclear location) as determined by immunofluorescence staining of methanol/acetone-fixed cells could be resolved by treating hybrid virus-infected cells with a hypotonic KCl solution before fixation. Upon this treatment hybrid virus-infected cells also showed nuclear U-antigen staining. The possibility of an association of T- and U-antigens with different nuclear subfractions in SV40-transformed cells was investigated. Detergent-cleaned nuclei of SV40-transformed cells were fractionated into nuclear matrices and a DNase-treated, high-salt nuclear extract. Analysis of the nuclear matrices by immunofluorescence microscopy with T+U+ and T+U- hamster SV40 tumor serum revealed that U-antigen remained associated with the nuclear matrices, whereas T-antigen could not be detected in this nuclear subfraction. T-antigen, however, could be immunoprecipitated from nuclear extracts of the SV40-transformed cells.
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PMID:Simian virus 40 T- and U-antigens: immunological characterization and localization in different nuclear subfractions of simian virus 40-transformed cells. 8 23

In an unconventional assay system (MEM Test) Caspary & Field claimed in 1971 to have detected lymphocyte sensitization to a common tumour antigen in all patients with cancer. There was no evidence of histogenetic specificity to the reaction and their conclusions are in direct contradiction to those of all workers who have studied the cytotoxic activity of lymphocytes on tumour cells. To improve the specificity of the test system, another type of tumour antigen was used in MEM Test incubation. Tumour-associated antigens were prepared according to the hypertonic salt extraction method introduced by Reisfeld, Leonard, Meltzer et al. As shown by the results, information could be gained concerning the existence of a malignant tumour and its location.
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PMID:Determination of cell mediated immunity against tumour associated antigens in patients of ENT. 8 6

The presence or absence of estrogen receptors in the nuclei of human breast tumor may be a useful tool in determining whether the tumor will or will not respond to endocrine therapy. This paper describes an assay which measures both unoccupied and occupied nuclear receptors in human breast cancer tumors. The assay was predicated on the fact that at low salt concentration, the nuclear receptor is bound to chromatin particles and can be separated from the soluble components containing proteolytic acitivity. Nuclear estradiol receptors were measured in human breast cancer tissue (MCF-7 cell line) and in DMBA (dimethylbenz(a)anthracene-induced rat mammary carcinomas) tumors. Complete translocation of the cytoplasmic receptor in the MCF-7 cells was observed compared to only 35-50% of the cytoplasmic receptors seen in the nucleus of the DMBA tumor after estradiol injection. The study also showed 6 pmol/mg DNA for total unoccupied nuclei and cytoplasmic estrogen receptors, and 25% of it in the nucleus; this finding differed from Zava et al's finding of 2 pmol/mg DNA and 75% in the nucleus, probably because of differing methodology or use of a later passage of cell line. 29 out of the 34 tumors with cytoplasmic receptors were found to contain unoccupied nuclear receptors, indicating that free nuclear receptors are not exceptions. The assay used in this study is currently being used to determine the translocative ability of the cytoplasmic receptors in human breast carcinomas.
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PMID:Estradiol binding to nuclear receptors in human breast cancer tissue (MCF-7 cell line) and in dimethylbenz(a)anthracene-induced mammary carcinoma. 10 64


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