Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of protein kinase C (PKC) genes (alpha, beta, gamma and epsilon) was measured in cultured normal human neonatal melanocytes and metastatic melanoma cell strains. Three of the PKC isotypes (alpha, beta and epsilon) were constitutively expressed in neonatal melanocytes. Protein kinase C beta RNA transcripts were induced in neonatal melanocytes cultivated in medium with serum and 12-O-tetradecanoylphorbol-13-acetate (TPA). In contrast, PKC alpha and epsilon RNA transcripts were detected in melanocytes cultivated in medium without serum and TPA, but were repressed in melanocytes cultivated in medium with serum and TPA. Only PKC alpha and epsilon RNA transcripts were detected in the melanoma cell strains and the PKC RNA transcript expression levels varied among the five metastatic melanomas. In four metastatic melanoma cell strains, PKC alpha and epsilon RNA transcript expression levels were repressed by serum, but in one melanoma cell strain, PKC alpha and epsilon RNA transcript expression levels were induced by serum. Protein kinase C gamma RNA transcripts were not detected in either the melanocytes or melanoma cell strains. These data suggest an alteration of PKC isotype gene expression in the progression of primary melanocytes to metastatic melanoma. The absence of the PKC beta RNA transcripts and altered expression of PKC alpha and epsilon isotypes in particular may be a feature in the transformation of human primary melanocytes.
Carcinogenesis 1991 Jan
PMID:The differential expression of protein kinase C genes in normal human neonatal melanocytes and metastatic melanomas. 198 68

Sphingosine and other long-chain (sphingoid) bases inhibit protein kinase C, the putative cellular receptor for the tumor promoter phorbol 12-myristate 13-acetate (PMA), and exert potent effects on diverse cell functions. We tested the ability of long-chain bases to modulate multistage carcinogenesis in mouse C3H/10T1/2 cells exposed to gamma-rays and PMA. Sphingosine and sphinganine completely blocked the enhancement of radiation-induced transformation by PMA (promotion) and partially suppressed transformation by radiation alone. N-Acetylsphingosine, a ceramide analog, did not inhibit transformation. Sphingosine was rapidly taken up by the cells and metabolized; hence, the long-chain bases were added daily to achieve prolonged inhibition. Long-chain bases inhibited protein kinase C activity in C3H/10T1/2 cells and suppressed the down-regulation of this enzyme by PMA. Our results establish that long-chain bases are highly effective inhibitors of carcinogenesis in this model. Our results also indicate that the suppressive effects may be mediated, in part, by inhibition of protein kinase C. The data suggest that sphingosine and other long-chain bases derived from complex sphingolipids may act as cancer-preventative agents.
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PMID:Long-chain (sphingoid) bases inhibit multistage carcinogenesis in mouse C3H/10T1/2 cells treated with radiation and phorbol 12-myristate 13-acetate. 200 Mar 99

Most chemicals that produce skin cancer are genotoxic by in vitro and in vivo short-term assays and produce a high incidence of skin cancer within a year if optimal doses are applied. If in long-term skin painting studies one or two tumours in 50 mice are observed there is a general consensus that no carcinogenic activity can be claimed and it has been suggested that if up to 10% tumours are induced by irritant substances this could be due to an enhancement of spontaneous tumour incidence. Observations of skin tumour incidences higher than 10% with non-genotoxic substances, usually after a long latent period, is considered to represent evidence for a non-genotoxic mechanism. Examples of such substances include croton oil, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), sodium hydroxide, potassium hydroxide, phenol, dodecylbenzene and petroleum-derived middle distillates. Two distinct mechanisms appear to be involved in the production of tumours by a non-genotoxic substance. The first of these is that seen with the strong promoting agents. These, by binding to and activating protein kinase C, appear to directly stimulate sustained epidermal hyperplasia without severe skin damage. The other appears to involve substances producing severe skin damage either by a direct caustic effect or by cumulative irritancy. These changes give rise to marked epidermal hyperplasia with repeated episodes of regeneration and damage. The tumour induction by both mechanisms probably results from oncogene activation and it is possible that oxidative enzymes from inflammatory cells may be involved in the activation process. Various reasons are given why non-genotoxic carcinogenesis in the skin is considered not to be relevant to man and ways of recognising and avoiding its occurrence in animals studies are recommended.
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PMID:Evidence for and possible mechanisms of non-genotoxic carcinogenesis in mouse skin. 204 89

The effects of cigarette smoke condensate (CSC) and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on gap junction structure, quantity and function were investigated. Gap junction morphology was studied in rotary-shadowed freeze-fracture replicas of primary chick embryo hepatocytes. CSC (24 micrograms/ml) induced a strong decrease of gap junction areas; within 6 h the areas were reduced by greater than 60%. In the first 3 h of exposure, TPA (100 ng/ml) also reduced gap junction areas, but in the next 3 h a partial recovery was observed. Protoplasmic fracture face centre-to-centre particle spacings were used as a measure for gap junction coupling. CSC had a slow (although not significant) reducing effect on particle spacings, while TPA induced a reduction from 10.6 nm (control) to 10.0 nm within 3 h, indicating a reduction of coupling. Gap junctions were quantified in thin sections of cultured chick embryo hepatocytes, V79 fibroblasts, and co-cultivated hepatocytes and V79 cells. CSC did not influence gap junction numbers in any of these cultures, while TPA treatment caused a disappearance of gap junctions between hepatocytes and between hepatocytes and V79 cells in the first 12 h of cultivation. In the following 36 h a slow recovery could be observed. Gap junctions between V79 cells had already disappeared within 30 min. Metabolic co-operation between hepatocytes and hypoxanthine-guanine phosphoribosyltransferase-deficient V79 cells was quickly and continuously blocked by CSC over 27 h, whereas the phorbol ester induced a transient block. The dissimilar effects of these compounds on both gap junction structure and function indicate that they act via different mechanisms. The finding that CSC did not inhibit phorbol ester protein kinase C binding and did not activate this protein kinase in vitro supports this hypothesis.
Carcinogenesis 1990 Jun
PMID:Effects of cigarette smoke condensate and 12-O-tetradecanoylphorbol-13-acetate on gap junction structure and function in cultured cells. 211 59

Exposure to ultraviolet (UV) radiation has been well correlated with skin cancer incidence. Long wave UV radiation (320-400 nm, UVA) is a major component of natural sunlight and cosmetic tanning 'salon' light, and has been shown not only to damage DNA and to act as a complete carcinogen, but also to promote ultraviolet B (280-320 nm, UVB) carcinogenesis. The mechanism by which the latter occurs is unknown, but it is believed to be related to the inflammation and irritation which results from UV exposure. In order to examine the possibility that UVA stimulates the same signalling pathway as do the phorbol esters, a class of much more thoroughly characterized skin tumor promoters, we exposed cells in culture to UVA radiation and measured cellular responses related to protein kinase C (PKC) activation. The data presented here demonstrate that a low, physiologic dose of UVA inhibits epidermal growth factor binding and increases PKC activity in cultured mammalian fibroblasts. The increase in cytosolic activity is not completely translocated to the membrane, and can be partially suppressed by puromycin and cycloheximide but not by actinomycin D. These observations are the first evidence to suggest that a protein which has been strongly linked to chemical tumor promotion may also be a critical mediator for UV-induced promotion. The response of cells to UVA is also unique, in that it does not cause a 12-O-tetradecanoyl phorbol-13-acetate-like rapid redistribution of PKC activity followed by down regulation.
Carcinogenesis 1990 Feb
PMID:Induction of protein kinase C activity by ultraviolet radiation. 215 38

Staurosporine, which is a potent inhibitor of protein kinases, such as protein kinase C, inhibited both inductions of adhesion of human promyelocytic leukemia cells (50% effective dose = 9.0 nM) and Epstein-Barr virus early antigen in Raji cells (50% effective dose = 3.4 nM) by teleocidin. However, staurosporine induced irritation on mouse ear and histidine decarboxylase activity in mouse skin. It did not induce ornithine decarboxylase activity in mouse epidermis. The two-stage carcinogenesis experiments of staurosporine were carried out at two different doses. Experiment 1 revealed that the group treatment with a single application of 100 micrograms of 7,12-dimethylbenz(a)anthracene, followed by repeated applications of 50 micrograms of staurosporine, resulted in 85.7% of tumor-bearing mice at Wk 30, whereas group treatment with staurosporine alone or 7,12-dimethylbenz(a)anthracene alone gave 6.7% and 0%, respectively. Experiment 2 showed that group treatment with 7,12-dimethylbenz(a)anthracene followed by applications of 10 micrograms of staurosporine resulted in 33% of tumor-bearing mice at Wk 30. In addition, staurosporine treatment reduced the percentages of tumor-bearing mice treated with teleocidin from 100% to 67% in Wk 15. These results demonstrated that staurosporine is a weak tumor promoter of mouse skin compared with teleocidin, but staurosporine has some potency to inhibit tumor promotion by teleocidin.
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PMID:Tumor-promoting activity of staurosporine, a protein kinase inhibitor on mouse skin. 216 51

Recent studies of the effects of dietary fat on experimental carcinogenesis have probed the influence of the dietary fat source, the time during carcinogenesis when a high-fat diet is fed, the interactions between fat and calories, and the potential mechanisms for the observed effects of fat on cancer. The essential fatty acids in the fat, the degree of their unsaturation, and the location of the unsaturation are all important in determining the influence of a dietary fat source on carcinogenesis. In addition, alterations in dietary fat can modify various sites and forms of cancer differently. Dietary fat has been clearly shown to be important in the promotion of cancer, and recent studies indicate that dietary fat can also be a factor in the initiation of cancer. Although the calories contributed by a high-fat diet also factor into cancer enhancement, dietary fat appears to contribute more than its high-caloric density. One potential mechanism for the influence of dietary fat on carcinogenesis is through modulating the activation of protein kinase C.
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PMID:The influence of dietary fat on carcinogenesis: lessons from experimental models. 218 10

A sharp decrease in the number of epidermal growth factor receptors (EGF-R) in the rat liver plasma membranes had been found at different stages of diethylnitrosamine-induced carcinogenesis. The complete loss of high-affinity binding sites for EGF did not prevent EGF-dependent autophosphorylation of EGF-R. Hepatocytes from the rat liver tumors in the primary culture had two classes of EGF-R: high and low affinity ones, though their number had been twice less than in the normal hepatocytes. The dynamics of internalization and down-regulation of EGF-R was very similar in the primary culture of transformed and normal hepatocytes. It testifies that there are some factors of microenvironment in the liver during carcinogenesis which cause the loss of EGF-R (down-regulation) and a decrease of their affinity (activation of protein kinase C). A possible autocrine or paracrine nature of these factors is discussed.
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PMID:[Changes in the epidermal growth factor receptors in the liver cells of rats in N-nitrosodiethylamine-induced hepatic carcinogenesis]. 222 52

We previously described epidermal proteins with molecular weights of 40,000 (p40) and 34,000 (p34) as target proteins of protein kinase C in mouse skin carcinogenesis in vivo. In the present work, p40 was purified from mouse brain by the use of 32P-labeled p40 of BALB/MK-2 cells as a tracer. Following four lines of evidence indicate that p40 is creatine phosphokinase B. 1) The amino acid sequences of all peptide fragments of p40 from mouse brain were located in the primary structure of creatine phosphokinase B. 2) p40 of BALB/MK-2 cells was immunoprecipitated with goat antibody against human creatine phosphokinase B. 3) p40 of BALB/MK-2 cells was absorbed to and eluted from a creatine affinity column. 4) Purified creatine phosphokinase B was phosphorylated in vitro by purified protein kinase C, but not by cAMP-dependent kinase or casein kinase II.
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PMID:Purification and identification of creatine phosphokinase B as a substrate of protein kinase C in mouse skin in vivo. 225 26

The anti-cancer drugs Adriamycin (ADR) and Daunomycin (DAU) alone were unable to inhibit the promotion of skin papillomas by repeated applications of 8.5 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA) in 7,12-dimethylbenz(a)anthracene (DMBA)-initiated mice. Pretreatments with 50 micrograms of ADR also failed to alter the tumor-promoting activities of smaller doses of TPA. Therefore, the effects of the anthracycline antibiotics on skin tumor promotion were evaluated in combination with the Ca2+ antagonist verapamil (VRP) and the protein kinase C (PKC) inhibitor palmitoylcarnitine (PC), compounds known to circumvent drug resistance. When applied simultaneously with each promotion treatment with 8.5 nmol of TPA, 2.5 mg of VRP inhibited the number of papillomas/mouse by 26%. But the combination of VRP + 50 micrograms of ADR or DAU inhibited the yields of papillomas by 50 or 47%, respectively, suggesting that VRP was required to reveal the antitumor-promoting activities of otherwise ineffective drugs. Similarly, the promotion of skin tumors by TPA was inhibited synergistically by the combinations of 2 mumol of PC + 50 micrograms of ADR or DAU. For instance, ADR and DAU had no effects alone but inhibited the incidence of skin papillomas by 78 and 86%, respectively, in the presence of PC, a compound which alone inhibited the tumor incidence by only 44%. The results indicate that ADR and DAU are effective against the promoting component of skin carcinogenesis only if they are applied in combination with Ca2+ antagonists or PKC inhibitors at a time when they can inhibit the early biochemical effects induced by TPA.
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PMID:Inhibition of mouse skin tumor promotion by adriamycin and daunomycin in combination with verapamil or palmitoylcarnitine. 226 12


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