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)

We have established a clonal cell line, PC-G2, from an experimentally induced rat pheochromocytoma. Administration of nerve growth factor to PC-G2 causes a 4- to 8-fold induction in the specific activity of tyrosine hydroxylase [tyrosine 3-monooxygenase; L-tyrosine,tetrahydropteridine:oxygen oxidoreductase(3-hydroxylating); EC 1.14.16.2]. The response is elicited in a dose-dependent fashion, at concentrations above 0.1 microgram/ml. Antiserum to nerve growth factor inhibited the induction of tyrosine hydroxylase. Dexamethasone enhances the nerve growth factor-mediated elevation of tyrosine hydroxylase. After 3--4 days of exposure to nerve growth factor the maximal induction of tyrosine hydroxylase is seen, although a significant increase can be observed after 24 hr. In contrast to the PC-12 cell line (derived from the same tumor), in which neurite outgrowth occurs in response to nerve growth factor, there is no morphological change or alteration in growth rate of PC-G2 cells after exposure to nerve growth factor.
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PMID:Nerve growth factor-mediated induction of tyrosine hydroxylase in a clonal pheochromocytoma cell line. 3 87

The hydroxylation rate and rate of tyrosine catabolism are measured by injection of ring-deuterated L-phenylalanine and ring-deuterated L-tyrosine and subsequent deuterium determination in the water fraction of the blood. The hydroxylation rate was confirmed as the rate-limiting step. Whereas tyrosine catabolism yields normal Michaelis-Menten kinetics, homotropic activation is demonstrated for the hydroxylation step. In all tumor rats under study, the rates of phenylalanine hydroxylation and tyrosine catabolism are decreased. The delta-values to control increase with tumor age. In tumor rats, the hydroxylation step remains the rate-limiting one. Kinetic data indicate that the decrease in hydroxylation is due to a decreased turnover rate of the enzyme, whereas the increase in tyrosine catabolism is caused by the branching off of tyrosine or an intermediate on the route to D2O formation. The results are discussed with respect to altered levels of tetrahydrobiopterin, phenylalanine and tyrosine found during parallel investigations.
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PMID:In vivo metabolism of deutero-L-phenylalanine and deutero-L-tyrosine in normal and in various tumor-bearing rats. 61 24

Coculture of purified murine T cells with anti-CD3 monoclonal antibody (145-2C11) results in the induction of nonspecific cytotoxic T lymphocytes (CTL) with MHC-unrestricted cytolytic activity against a range of tumor targets. Serine proteases associated with effector cell granules are among the molecules postulated to play a role in cell-mediated cytolysis. The present study examines the ability of exogenous serine protease substrates to inhibit anti-CD3-activated cytotoxic T (ACT) cell-mediated killing of P815 mastocytoma and YAC1.2 lymphoma target cells. The chymotrypsin substrate N-acetyl-L-tyrosine ethyl ester (ATEE) was found to significantly inhibit ACT cell-mediated cytolysis. In contrast, the trypsin substrate N-benzoyl-L-arginine ethyl ester (BAEE) had little, if any, effect on ACT cell-mediated cytolysis. These effects were observed with both target cell populations. Conjugate inhibition studies performed with ATEE indicated that a chymotrypsin-like serine protease is involved in a postbinding event during cytolysis. Pretreatment of either target or effector cells with ATEE prior to cytolytic assay revealed that the chymotrypsin-like serine protease involved in cytotoxicity is of effector cell origin. Northern blot analysis of total RNA extracted from ACT cells revealed the presence of transcripts coding for CCP1 and CCP2 serine proteases known to be involved in antigen-specific CTL function, but little or no expression of the HF serine protease which has also been implicated in antigen-specific CTL killing. CCP2 exhibits chymotrypsin-like activity while HF displays trypsin-like activity. On the other hand, the CCP1 gene product has protease activity which resembles neither chymase nor tryptase activities. Thus, the level of mRNA expression for these serine proteases is consistent with our earlier observations, using the serine protease substrates, that a chymotrypsin-like serine protease but not a trypsin-like serine protease is involved in ACT cell-mediated cytolysis. "Lymphocyte panning" of ACT cells revealed abundant CCP1 and moderate CCP2 mRNA expression in CD4- and CD8+ anti-CD3-activated T cells with strong tumoricidal activity. CD8- anti-CD3-activated T cells with moderate cytolytic activity also expressed substantial levels of CCP1 and CCP2 mRNA, suggesting that both CD4- CD8- and CD4- CD8+ ACT cells participate in killing tumor targets. In contrast, CD4+ anti-CD3-activated T cells lacked both cytolytic activity and significant CCP1 and CCP2 mRNA expression. These findings are consistent with the involvement of chymotrypsin-like, as well as other, serine proteases in CTL-mediated lysis.
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PMID:Expression and utilization of chymotrypsin-like but not trypsin-like serine protease enzymes by nonspecific T killer cells activated by anti-CD3 monoclonal antibody. 153 39

Normal and abnormal processes of cellular invasion often are initiated by degradation of basement membranes. The process of corneal ulceration might operate via similar mechanisms; degradation of the corneal stroma is not seen until after the basement membrane underlying the corneal epithelium in the preulcerative lesion is lost. Recent data implicate a member of the matrix metalloproteinase (MMP) family of enzymes, 92 kD gelatinase/type IV collagenase (MMP-9) in both cellular invasion processes and degradation of epithelial basement membrane before corneal ulceration. This suggests that use of nontoxic substances that block activity of MMP-9 might be useful in preventing or inhibiting pathologic invasion processes in vivo. An agent that fits these criteria is N-[D,L-2-isobutyl-3(N'-hydroxycarbonylamido)-propanoyl]-O- methyl-L-tyrosine methylamide, which previously has been characterized as an inhibitor of tumor cell collagenases. In this study, the authors show that the inhibitor can efficiently block activity of MMP-9 purified from cultures of rabbit corneal epithelial cells. Results suggest that the recently reported efficacy of a closely related inhibitor in blocking progression of alkali burns to ulceration might be attributable to its action against MMP-9.
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PMID:An inhibitor of the matrix metalloproteinase synthesized by rabbit corneal epithelium. 165 75

Variants of the Bomirski family of hamster melanomas whose proliferative rates differ inversely with the genetically determined degree of melanogenesis were probed for two proteins critical in melanogenesis: tyrosinase and catalase-B (gp 75). The parental black tumor Ma contained both proteins in abundance. The amelanotic variant Ab, inducible in culture with L-tyrosine or L-dopa to form melanosomes and to melanize, had minimal tyrosinase, despite high levels of (tyr)mRNA, and no gp 75. Variant MI, hypomelanotic despite abundant tyrosinase, and synthesizing predominantingly pheo-(red) melanin, expressed barely detectable gp 75. These findings suggest a regulatory control of melanogenesis distal to (tyr)mRNA and strengthen the hypothesis that in vivo tyrosinase without catalase-B favors pheo- over eumelanogenesis.
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PMID:Molecular mechanisms governing melanogenesis in hamster melanomas: relative abundance of tyrosinase and catalase-B (gp 75). 167 30

Creation of an amino acid imbalance, particularly curtailment of L-methionine, at the tumor cell level is thought to have a favorable effect on the inhibition of tumor growth. In the present study, we examined the influence of a specially-formulated amino acid mixture, avoid of sulfur-containing amino acids (L-methionine and L-cysteine), on the growth and amino acid fraction of Sato lung carcinoma (SLC) and the host metabolism in SLC-bearing rats. The rats were treated by total parenteral nutrition containing the above amino acid mixture, plus other nutrients (methionine-deprived TPN) for 10 days. Tumor growth began to decrease 4 days after the start of this treatment and the size was significantly less at the end of the treatment than in rats receiving conventional TPN with general purpose Vuj-N type amino acid solution as a protein source. The tumor-to-carcass weight ratio also showed a similar trend. In biochemistry, the albumin level and albumin-to-globulin ratio were significantly lower than in the rats receiving conventional TPN but other parameters such as total protein, glucose, GOT and GPT were not affected by the treatment. In the amino acid fraction of the tumor tissue extraction, both L-methionine and L-tyrosine were decreased and L-serine was increased significantly compared with the control group.
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PMID:Influence of L-methionine-deprived total parenteral nutrition on the tumor tissue and plasma amino acids fraction and the host metabolism: experimental study with Sato lung carcinoma-bearing rats. 249 79

The B16/C3 murine melanoma is a pigmented tumor that is rich in the copper-containing enzyme, tyrosinase. This enzyme, which converts tyrosine to melanin precursors, is largely associated with membrane fractions of cells and exists in a number of discrete isozymic forms ranging in molecular mass from 58,000 to 150,000 daltons and pI from 3.4 to 5.2. One of these isozymes (Mr = 58,000, pI 3.4) has been purified to homogeneity. The purified enzyme catalyzes the hydroxylation of L-tyrosine to L-dihydroxyphenylalanine (L-DOPA) and the conversion of L-DOPA to dopaquinone. Ascorbic acid, tetrahydrofolate, and dopamine can serve as cofactors in the hydroxylase reaction. The Michaelis constants for the purified enzyme were 7 X 10(-4) M for L-tyrosine and 6 X 10(-4) M for L-DOPA. The Vmax for L-DOPA was much greater than the Vmax for L-tyrosine indicating that tyrosine hydroxylation is rate-limiting in melanin precursor biosynthesis. Two putative copper chelators, phenylthiourea and diethyldithiocarbamide inhibited both the tyrosine hydroxylase and L-DOPA oxidase activities of the enzyme. Phenylthiourea was a noncompetitive inhibitor while diethyldithiocarbamide was a competitive inhibitor indicating that these agents act by different mechanisms. When digested with proteases and glycosidases, higher molecular weight forms of tyrosinase co-migrated with the purified enzyme in isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggesting that the isozyme was derived from larger precursors. Thus, post-translational processing of tyrosinase may underlie isozyme diversity and this may be important in the control of melanogenesis in this tumor model.
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PMID:Tyrosinase isozyme heterogeneity in differentiating B16/C3 melanoma. 309 4

Induction of a microsomal Ca2+-dependent serine protease by hepatic tumor promoters was studied. Male F344 rats were fed a diet containing one of the following promoting agents: phenobarbital (CAS: 50-06-6), dichlorophenyltrichloroethane (CAS: 50-29-3), butylated hydroxytoluene, ethyl-alpha-chlorophenoxyisobutyrate (CAS: 128-95-0), or 17-alpha-ethynylestradiol (CAS: 57-63-6) or a nonpromoting agent, diphenylhydantoin (CAS: 57-41-0), for 1 week. By treatment with promoters, the protease activity in the microsomal fraction was increased to threefold to fivefold that of control, whereas only a slight increase of activity was found after diphenylhydantoin treatment. The Ca2+-dependent protease activity was determined with the use of N-benzoyl-L-tyrosine ethyl ester as the substrate in a medium containing 50 mM CaCl2 for its maximal activity. This protease was preferentially localized in the smooth microsomal membrane and strongly inhibited by diisopropyl phosphorofluoridate (CAS: 55-91-4), and the optimum pH of the activity was 7.8. It appears that the Ca2+-dependent serine protease measured by using a chymotrypsin substrate is a novel protease, and induction of its activity by hepatic tumor-promoting agents is a common and specific phenomenon.
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PMID:Induction of a novel Ca2+-dependent chymotrypsin-like serine protease by tumor promoters in rat livers. 352 96

Macrophage-like tumor cells can be obtained in large quantities as rather homogeneous populations, making these cells useful for chemotaxis assays. Therefore, macrophage-like cells J774A, WEHI-3, P388D1, IC-21, and NCTC 1469, all of murine origin, and U937 of human origin, were tested for chemotactic activity to a number of chemoattractive agents, such as casein, an N-formyl tetrapeptide (N-formyl-L-norleucyl-L-leucyl-L-phenylalanyl-L-tyrosine), and culture supernatants of murine SL2 lymphoma cells. J774A and WEHI-3 macrophage-like cells of murine (BALB/c) origin expressed the strongest chemotactic activity to casein and N-formyl tetrapeptide, respectively. The results show that: very standardized chemotaxis assays can be performed using these cell lines; these assays require appropriate cell line-stimulus combinations; there are substantial differences among cell lines as to sensitivity to various chemoattractive substances; macrophage cell lines and functional mutants may be helpful for the study of receptors for chemotaxins and the study of transducer signals for chemotaxis.
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PMID:Macrophage-like tumor cells as tools to study chemoattractive activity. 386 10

Nine new palladium(II) complexes of the formula [Pd(bipy)(AA)]n+ (where bipy is 2,2'-bipyridine, AA is an anion of L-cysteine, L-aspartic acid, L-glutamic acid, L-methionine, L-histidine, L-arginine, L-phenylalanine, L-tyrosine, or L-tryptophan, and n = 0 or 1) have been synthesized by interaction of [Pd(bipy)Cl2] with an appropriate sodium salt of amino acid in water. These palladium(II) complexes have been characterized by chemical analysis and by visible, infrared, and 1H NMR spectroscopy. The modes of binding of amino acids in these palladium complexes have been ascertained by infrared and 1H NMR spectroscopy. The molar conductances of these complexes in water suggest that they are either nonelectrolytes or 1:1 electrolytes. These palladium complexes have shown growth inhibition against L1210 lymphoid leukemic, P388 lymphocytic leukemic, Sarcama 180, and Ehrlich ascites tumor cells. Some of these complexes show I.D.50 values comparable to or lower than cis-diamminedichloroplatinum(II).
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PMID:Some potential anticancer palladium(II) complexes of 2,2'-bipyridine and amino acids. 394 1


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