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

Tumour growth was shown to be associated with DNA breakdown in thymocytes of rats bearing Zajdela ascites hepatomas. The tumour action on the thymus is mediated through adrenal glands since bilateral adrenalectomy completely prevents DNA breakdown in thymocytes. Using Southern hybridization of DNA genome with probes for histone, ribosomal and heat shock gene (hsp 70), it was shown that the degradation products of specific DNA sequences are as heterogenous as those of total DNA, although marked differences in appearance of nucleosomal ladder were seen. These data were interpreted to indicate different patterns of DNA breakdown in dying thymocytes. DNA breakdown in thymocytes in vivo and in isolated rat liver nuclei in vitro seems to proceed by similar mechanisms.
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PMID:[Glucocorticoid-mediated degradation of DNA in thymocytes of rats with transplantable Zajdela ascites hepatoma]. 367 4

The phosphorylating enzymes of human skin were studied in bioptic samples of normal tissue (18 samples) and tumors (21 cases), melanomas and basaliomas, which developed in different regions of head and face. The activity of cAMP-dependent and cAMP-independent protein kinases was tested in skin extracts using histone HI and casein as substrates of phosphorylation, respectively. In most tumors the casein kinase activity was found to be significantly elevated (about 10-fold) as compared with normal counterparts. The histone kinase activity was only slightly elevated in tumors (by 30%). For each bioptic sample the ratio of histone kinase activity versus casein kinase activity was calculated. In normal skin this ratio constituted from 1 to 3.7, while in 90% of samples it was higher than 1.5. In all tumors except one the ratio was decreased down to 0.2-0.9. The effect did not depend upon the type of malignancy and tumor location. The change in the protein kinase ratio is considered to be a specific feature of transformed tissue.
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PMID:[Changes in protein kinase activity of the skin in cancer]. 372 63

High mobility group (HMG) proteins 14 and 17 bind to mononucleosomes in vitro, but the exact nature of this binding has not been clearly established. A new method was developed to allow direct membrane transfer of DNA from HMG 14/17 bound and unbound nucleosomes, which have been separated by acrylamide gel electrophoresis. Hybridization analysis of membranes obtained by this method revealed that the HMG 14/17 bound nucleosomes of avian erythrocytes and rat hepatic tumor (HTC) cells were enriched, about 2-fold, in actively transcribed genes and also inactive but DNase I sensitive genes. Nucleosomes containing inactive, DNase I resistant genes were bound by HMG 14/17, but not preferentially. Several factors that have been reported to greatly influence the binding of HMG 14/17 to nucleosomes in vitro were tested and shown to not account for the preferential binding to DNase I sensitive chromatin. These factors include nucleosomal linker DNA length, single-stranded DNA nicks, and DNA bulk hypomethylation. An additional factor, histone acetylation, was preferentially associated with the HMG 14/17 bound chromatin fraction of avian erythrocytes, but it was not associated with the HMG 14/17 bound chromatin fraction of metabolically active HTC cells. The latter finding was true for all kinetic forms of histone acetylation.
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PMID:Preferential in vitro binding of high mobility group proteins 14 and 17 to nucleosomes containing active and DNase I sensitive single-copy genes. 373 Mar 69

Treatment with a single dose of 21 mg/kg, of 1,2-dimethylhydrazine was followed by a significant decrease in the level of cAMP-dependent protein kinase (histone kinase) in rats' large bowel mucosa after 72 hrs. However, its level returned to basal value after 2 weeks, with casein kinase level remaining unchanged. Both carcinogen--induced tumors of the large bowel and adjacent mucosa showed a drop in protein (mol. wt.-50 kdalton) was enhanced in tumor considerably.
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PMID:[Protein kinase activity and phosphorylation of endogenous proteins in the rat colonic mucosa during chemical carcinogenesis]. 373 97

Calcium-activated, phospholipid-dependent protein kinase (C kinase) is activated by diacylglycerol which is produced in the signal-induced turnover of inositol phospholipid. C kinase has a important role in the transduction of extracellular signals of cellular function, proliferation and differentiation. C kinase in pig epidermis was investigated. Pig epidermal homogenates were centrifuged at 30,000 g for 30 min, and the supernatant was applied on a DEAE-cellulose column for purification. The partially purified enzyme was stimulated by simultaneous addition of Ca2+ and phosphatidylserine. Small amount of diolein or 12-o-tetradecanoylphorbol-13-acetate (TPA) further activated the enzyme activity. Polyprenoic acid (E5166) which is a newly-synthesized retinoic acid derivative inhibited the TPA activation of C kinase. This inhibition may explain the mechanism in which retinoids inhibit TPA-induced tumor promotion. C kinase preferentially phosphorylated seryl and threonyl residues of lysine-rich histone. Endogenous C kinase phosphorylated 97kD pig epidermal soluble protein. This protein was phosphorylated immediately. With two dimensional polyacrylamide gel electrophoresis, it was shown to be a basic protein.
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PMID:[Studies of calcium-activated, phospholipid-dependent protein kinase in pig epidermis]. 375 16

The effects of protein kinase C inhibitor H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine) on tumor-promoting phorbol ester induced inhibition of vincristine uptake in P388 murine leukemic cells were investigated with the objective of assessing the possible role of Ca2+-activated, phospholipid-dependent protein kinase (protein kinase C) in vincristine uptake. 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a potent inhibitor at concentrations above 1 nM. Other phorbol esters also inhibited vincristine uptake in approximate proportion to their activity in competing for [20-3H]phorbol 12,13-dibutrate binding. TPA enhanced the Ca2+-activated, phospholipid-dependent phosphorylation of histone III-S by a soluble protein fraction of cells. Phosphorylation of various cell lysate proteins (p18, p21, p29, p34 and p45) were also stimulated by TPA. These TPA-induced stimulations were also inhibited dose-dependently by H-7. It is tentatively concluded that the phosphorylation of cell lysate protein substrates by protein kinase C may be an important mechanism linked to the regulation of vincristine uptake in leukemic cell.
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PMID:An inhibitor of protein kinase C, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine(H-7) inhibits TPA-induced reduction of vincristine uptake from P388 murine leukemic cell. 376 16

Adenylate cyclase activity in purified rat adipocyte membranes is stimulated by the calcium- and phospholipid-dependent enzyme protein kinase C. Over the concentration range of 100-1000 milliunits/ml, both highly purified (approximately 3000 units/mg of protein) protein kinase C from rat brain and partially purified (14 units/mg of protein) protein kinase C from guinea pig pancreas stimulate cyclase activity. The actions of both protein kinase C preparations on adenylate cyclase activity are dependent on added calcium, which is effective at concentrations less than 10 microM. Exogenous phospholipids are not required for stimulation of adenylate cyclase by protein kinase C; but, under typical cyclase assay conditions, the adipocyte membranes satisfy the lipid requirement for protein kinase C phosphorylation of histone. The tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate enhances the kinase action on cyclase, and the phorbol ester is effective at concentrations equimolar with the kinase (less than 10 nM). With the brain protein kinase C, 12-O-tetradecanoylphorbol-13-acetate effects are especially evident at limiting calcium concentrations. Inhibitors of protein kinase C activity, such as chlorpromazine, palmitoylcarnitine, and polymyxin B, inhibit selectively that adenylate cyclase activity which is stimulated by protein kinase C plus calcium. It is concluded that protein kinase C acts directly on the adipocyte adenylate cyclase system.
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PMID:Activation of adipocyte adenylate cyclase by protein kinase C. 377 40

Treatment of 3T3-L1 cells with 0.1-1.0 nM insulin results in rapid (5-15 min) activation of a soluble protein kinase that phosphorylates serine residues in ribosomal protein S6. The insulin-stimulated kinase activity is detectable in confluent, nongrowing preadipocytes and adipocytes. In the presence of 2 micrograms of cycloheximide per ml, preconfluent 3T3-L1 cells also respond to insulin by acquiring an S6 kinase activity whose properties are the same as those of the enzyme activity elicited by insulin alone in growth-inhibited cells. The principal insulin-stimulated S6 kinase has a Mr of approximately equal to 50,000-60,000; there is a variable amount of activity that sediments with a Mr of about 80,000. The soluble enzyme exhibits optimal activity between pH 8 and pH 9, requires Mg2+ (10-20 mM), and is inhibited by Ca2+ (0.5 mM), Mn2+ (0.05 mM), and NaF (30 mM). GTP cannot substitute for ATP in the phosphotransferase reaction; cAMP, cGMP, phosphatidylserine plus diolein, the cAMP-dependent protein kinase inhibitor, and heparin (0.7 micrograms/ml) are without effect. Although treatment of 3T3-L1 cells with insulin does not influence the activity or the subcellular distribution of the phospholipid and Ca2+-dependent protein kinase C, exposure to the phorbol tumor promoter phorbol 12-myristate 13-acetate (PMA) results in translocation of protein kinase C to the membrane and activation of a soluble phospholipid and Ca2+-independent S6 protein kinase that has the same magnitude of activity and sedimentation behavior as the insulin-induced activity. Trypsin treatment of either 3T3-L1 cytosolic extracts or partially purified 3T3-L1 protein kinase C generates a small amount of S6 kinase activity of Mr 50,000. This activity, resolved by sucrose gradient centrifugation, is less active than that elicited by either insulin or PMA and, unlike the activities generated by insulin and PMA, is associated with histone kinase activity. The data suggest that the S6 kinase elicited by either insulin or PMA is neither protein kinase C, its phospholipid, and Ca2+-independent proteolytic derivative nor the result of proteolytic activation of an inactive proenzyme that can be reproduced by trypsin treatment of cell extracts in vitro.
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PMID:Activation of S6 kinase activity in 3T3-L1 cells by insulin and phorbol ester. 389 33

The specific activity (dpm/mg protein) of the acid-soluble nuclear material extracted from spleens or lymph nodes (but not other tissues) of tumor-bearing BALB/c mice was approximately twice that of the corresponding tissues from tumor-free mice of the same age and sex following i.p. injection of L-[U-14C]lysine. Autoradiography of gel electrophoretograms showed the major increases in radioactivity to be in histone H2A and histone H2B. Rabbit anti-mouse lymphocyte serum could prevent the splenic response to tumor only if the serum was given at the time of, or very soon after, the tumor transplant. Immunization with sheep red blood cells or with bovine serum albumin in adjuvant did cause an increase in specific activity of the splenic acid-soluble nuclear material, but there was little difference between samples from normal and tumor-bearing mice when the nuclei were purified before extraction. Use of adjuvant, with or without antigen, prevented the tumor-induced increase in the specific activity of the acid-soluble, histone fraction. Thus, adjuvant-induced suppressor cells were able to interfere with lysine incorporation. It was concluded that the tumor must grow within the host for this manifestation, since mice which were immune to the tumor as a result of vaccination had no increase in lysine incorporation, compared to normal, untreated mice. However, vaccinated mice which did not develop immunity had tumor growth and the associated increased splenic histone synthesis. A regulatory role is suggested for the histones H2A and H2B.
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PMID:Increased synthesis of acid-soluble nuclear material in spleens of tumor-bearing BALB/c mice. 392 Dec 40

Exposure of various cell types (rat-1 fibroblasts, bovine adrenocortical cells, human lymphoid cells) to nanomolar concentrations of TPA, resulted in a rapid, apparent loss of cellular protein kinase C content, when the enzyme was assayed by its phospholipid and Ca2+-dependent histone (H1)-kinase activity, following solubilization and DEAE-cellulose chromatography isolation. By contrast, no loss of protein kinase C was detected when the enzyme was probed by its high affinity PDBu binding capacity nor when the kinase activity was assayed with protein substrates other than histones, such as vinculin and a cytochrome P-450. It is concluded that, in addition to the previously reported enzyme subcellular redistribution, following TPA treatment, the phorbol ester induces striking alterations of the cellular protein kinase C catalytic activities. The molecular mechanisms of these changes and their implication in the tumor promotion process remain to be clarified.
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PMID:Altered catalytic properties of protein kinase C in phorbol ester treated cells. 394 56


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