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

The recent development of sensitive methods to detect carcinogen-DNA adducts offers a useful biochemical approach to human risk assessment. However, a major obstacle to developing a human biomonitoring method for carcinogen-DNA adducts has been the problem of obtaining target tissue DNA samples by non-invasive means. This work describes a method for the isolation of nanogram quantities of DNA from urothelial cells exfoliated into urine and the detection of carcinogen-DNA adducts from that DNA by 32P-postlabelling methods. Urine samples were collected on ice from dogs treated with 4-aminobiphenyl (ABP) over a 2-week period and pooled according to an experimental plan that involved analysis of cumulative 48- or 72-h samples. The pooled samples were sieved and then washed repeatedly with a sucrose buffer to dissolve contaminating triple phosphate (MgNH4PO4), calcium oxalate and uric acid crystals. DNA was isolated using an enzyme-solvent extraction method with the DNA being co-precipitated from ethanol with glycogen. The DNA was hydrolysed and postlabelled with 32P under conditions of excess ATP so that nucleotides were labelled quantitatively. Adducts observed on the resulting thin-layer chromatograms were identical to those obtained from DNA modified in vitro with N-hydroxy-4-aminobiphenyl and from dog bladder urothelial DNA isolated from the ABP-dosed animals at termination of the experiment. Furthermore, a dose-related increase in ABP-DNA adduct formation was demonstrated. Thus, it appears that the carcinogen-DNA adduct levels in the exfoliated bladder cells are reflective of the levels in the intact urothelium once steady-state levels have been achieved. To establish the identity of the major ABP-urothelial DNA adduct in chronically-treated dogs, the predominant 32P-postlabelled adduct was eluted from the thin-layer chromatograms and co-injected on an HPLC system with a synthetic [3H]N-(deoxyguanosin-8-yl)-4-aminobiphenyl-3',5'-bisphosphate standard. Dual-label analysis of 3H and 32P indicated that both eluted from the column in the same fraction, which coincided with the UV absorbance peak of the synthetic marker. Preliminary experiments with exfoliated urothelial cells from human urines indicate that these methods should have general utility for monitoring humans exposed to urinary bladder carcinogens and for investigations of the biochemical mechanisms by which such adducts are formed in the urothelium.
Carcinogenesis 1990 Apr
PMID:Detection and characterization of carcinogen-DNA adducts in exfoliated urothelial cells from 4-aminobiphenyl-treated dogs by 32P-postlabelling and subsequent thin-layer and high-pressure liquid chromatography. 232 2

The differential effects of cigarette smoke condensate (CSC) and its fractions (neutral, basic, and acidic fractions) on proliferation and squamous differentiation of normal human bronchial epithelial (NHBE) cells versus human lung carcinoma cells were investigated. CSC, and the neutral and acidic fractions inhibited cellular proliferation more than the basic fraction. When compared to the acidic and basic fractions, CSC and the neural fraction were more effective in causing squamous differentiation of NHBE cells and inhibiting specific binding of phorbol dibutyrate (PDBU). There were no significant changes in ionized cytosolic calcium concentration when NHBE cells were treated with CSC. In contrast to the normal epithelial cells, neither HUT-292 nor the 3 other carcinoma cell lines examined showed marked squamous morphological changes when exposed to either CSC or its fractions and the carcinoma cells were more resistant to their inhibiting effects on cellular proliferation. These results are consistent with the hypothesis that differential effects of tobacco smoke components on cellular proliferation may allow clonal expansion of preneoplastic and neoplastic human bronchial epithelial cells during lung carcinogenesis.
 ...
PMID:Differential effects of cigarette smoke condensate and its fractions on cultured normal and malignant human bronchial epithelial cells. 232 82

Aldehydes are ubiquitous compounds which are generated from many both endogenous and exogenous sources. Primarily because certain aldehydes are respiratory toxicants and carcinogens in laboratory animals, and also because they are present in both tobacco smoke and automotive emissions, cultured human bronchial cells have been used to study the ability of aldehydes, i.e., acrolein and formaldehyde, to cause pathobiological effects associated with carcinogenesis. Comparative studies indicate that each aldehyde distinctly affects several molecular and cellular variables including colony-forming efficiency, clonal growth rate, membrane integrity, formation of cross-linked envelopes, levels of cytosolic free calcium, low-molecular-weight thiol status, DNA structure, i.e., formation of DNA single-strand breaks and DNA-protein cross-links, and various DNA repair mechanisms. In relation to the toxicity exerted by these agents, acrolein induces differentiation more readily than formaldehyde whereas formaldehyde causes much higher levels of genetic damage than acrolein. However, for all biological endpoints measured, acrolein on a molar basis is always more potent than formaldehyde. Taken together, a variety of effects that relate to cell death, accelerated epithelial terminal differentiation and genotoxicity are associated with aldehyde exposure, which in human airways may have a role in the pathogenesis of various diseases. In the development of cancer, the possible contribution of aldehydes from both intra- and extra-cellular sources may partly depend on the ability of target cells to detoxify and counteract those aldehyde-related effects believed to critically relate to multi-stage carcinogenesis.
 ...
PMID:In vitro studies of aldehyde effects related to human respiratory carcinogenesis. 234 11

A procedure was developed for the per cell estimation of catalase activities in suspensions and cultures of murine epidermal keratinocytes (MEKs). Per cell catalase activity in MEKs cultured in low Ca2+ medium was relatively constant during the proliferation phase of culturing, but increased approximately 100% within 24 h of cessation of cell division. 12-O-Tetradecanoylphorbol-13-acetate (TPA) treatment of proliferating MEKs cultured in low Ca2+ medium resulted in (i) an initial suppression of proliferation, (ii) the accelerated detachment and differentiation of detached MEKs and (iii) a suppression of catalase induction in the detached population. Induction of MEK differentiation by raising the medium Ca2+ concentration resulted in rapid inhibition of cell division and approximately 200% increases in per cell catalase activities. Addition of TPA immediately prior to Ca2+ shift completely suppressed the Ca2(+)-dependent increases in activity. However, the addition of TPA 48 h after the induction of differentiation by Ca2+ shift had no effects on the elevated, pre-existing catalase activities. Per cell catalase activities varied in vivo with the stage of MEK differentiation. Specifically, the lowest and highest per cell activities (approximately 4-fold difference) were measured in enriched basal cell and spinous cell populations respectively. Catalase activity in the more differentiated MEKs was reduced approximately 33% within 24 h of topical treatment of dorsal skin with a promoting dose of TPA. However, catalase activity in enriched basal cell preparations was unaffected. Collectively, these studies demonstrate that per cell catalase activities increase as MEKs differentiate, and that TPA suppresses the increases in catalase activities that normally occur during differentiation.
Carcinogenesis 1990 Jun
PMID:Modulation of catalase activities in murine epidermal cells as a function of differentiation and exposure to 12-O-tetradecanoylphorbol-13-acetate. 234 71

The effects of 2 levels of dietary calcium and 2 types of dietary fat on the promotional phase phase of azoxymethane-induced colon cancer in the F344 rat were investigated. During the initiation phase of carcinogenesis all animals were fed a 5% corn oil AIN-76A diet containing 0.32% Ca in the form of calcium lactate. Rats were then injected with azoxymethane (AOM) weekly for 8 weeks. Thereafter, the rats were fed 1 of 3 diet formulations: a 5% corn oil diet or a 20% corn oil or 20% American Blend oil fat diet, with the level of Ca set at either 0.32% of the diet, a nutrient density simulating a daily human intake of approximately 1700 mg Ca/day, or at 0.04% of the diet, reflecting a human daily intake of approximately 200-250 mg of Ca/day, thus modeling 2 human nutrient density levels for calcium. Measurements of fecal pH during the experiment indicated an acidic adaptation of the large bowel to the lactate anion. Analysis of collected fecal samples showed more total fatty acids to be present in the colon when higher amounts of calcium were consumed. However, results of the tumorigenesis study indicated that calcium lactate fed at the 0.32% level significantly inhibited the development of colonic adenocarcinoma in all dietary groups. Taken together, this investigation supports the hypothesis that calcium supplementation can inhibit colon neoplasia in rats fed a high fat diet; however, under the conditions of this study, the 20% fat level did not significantly promote colon cancer as compared to a 5% fat level.
 ...
PMID:Inhibition of the promotional phase of azoxymethane-induced colon carcinogenesis in the F344 rat by calcium lactate: effect of simulating two human nutrient density levels. 239 78

1,8-Dihydroxy-3-methyl-9-anthrone (chrysarobin), a potent anthrone tumor promoter, reduced [125I] epidermal growth factor (EGF) binding to its receptor in primary epidermal cells from SENCAR mice maintained in low Ca2+ containing medium. The time course for this effect with chrysarobin was different from that of 12-O-tetradecanoylphorbol-13-acetate (TPA). Maximum inhibition of [125I]EGF binding was observed at 18 h versus 1 h respectively. Scatchard analyses revealed that the inhibition by chrysarobin was due to a decrease in the number of both high- and low-affinity classes of EGF receptors. In contrast, TPA caused a rapid inhibition of EGF binding, primarily due to a loss of high-affinity receptors. The mechanism by which chrysarobin inhibited the binding of EGF to its receptor involved neither direct activation nor membrane translocation of epidermal protein kinase C, whereas the rapid decrease in EGF binding induced by TPA was consistent with its ability to activate protein kinase C. Structure-activity relationships for EGF binding inhibition by anthrones revealed that inhibition was inversely proportional to chain length at the C10-position, which correlated closely with oxidation rate and skin tumor-promoting activity. alpha-Tocopherol was able to block partially the effect of chrysarobin but not TPA on EGF binding. These results suggest that oxidation at position C10 is at least partially responsible for the inhibition of EGF binding induced by chrysarobin. Furthermore, these studies support the hypothesis that changes in EGF receptor binding and/or function may play a role in skin tumor promotion by diverse classes of promoting agents.
Carcinogenesis 1990 Sep
PMID:Differential mechanism for the inhibition of epidermal growth factor binding to its receptor on mouse keratinocytes by anthrones and phorbol esters. 240 Oct 43

Two new mouse epidermal cell lines have been isolated and characterized as target cells for three chemical carcinogens. The ability to grow these cells at low density (approximately 5 clonogenic cells/cm2) has permitted more precise quantitation of chemical carcinogen-induced changes in epidermal differentiation. The cell lines, designated 291 and 271c, retain the property previously observed in primary cultures of mouse epidermal cells, that is the regulation of terminal differentiation by extracellular Ca2+ ion. Altered response to extracellular Ca2+ after carcinogen treatment of these cells is the basis of the assay endpoint. Other normal properties demonstrated by these cells are keratin immunofluorescence patterns, ability to form cornified envelopes in response to Ca2+ and a lack of tumorigenicity. Both of the lines have high cloning efficiencies (up to 20%) and characteristic epidermal morphology. Their chromosome number, however, is near tetraploid. Dose response studies indicated an increase in colonies with altered response to Ca2+ proportional to the dose of three chemical carcinogens: DMBA 0.001-0.5 microgram/ml X 24 h, MCA 0.01-5 micrograms/ml X 24 h and MNNG 0.01-0.2 micrograms/ml X 1 h. The optimized assay protocol has provided a reproducible means of quantitating carcinogen-altered epidermal cells relative to carcinogen dose, and of isolating cell clones for studies of altered differentiation in carcinogenesis and chemotherapy.
Carcinogenesis 1985 Sep
PMID:Mouse cell clones for improved quantitation of carcinogen-induced altered differentiation. 241 40

Mouse epidermal keratinocytes (MK cells) were grown as replicating subcultures at clonal density, in a serum-free, low calcium basal medium supplemented with seven different growth factors (Bertolero et al., Exp. Cell. Res. 155:64-80, 1984). This serum-free system was used to investigate the activity of fetal bovine serum (FBS) and of serum-derived factors on the growth and differentiation of MK cells. Unfractionated, whole FBS inhibited growth and induced terminal differentiation of normal MK cells. The growth inhibitory activity was considerably reduced by passing whole FBS over a resin (Chelex) to remove Ca2+ and other di- and trivalent cations. It is not known whether this treatment removed other factors. Addition of individual serum components either stimulated or inhibited cell-growth and differentiation. Fetuin, a major alpha-globulin of FBS, and high density lipoprotein strongly inhibited the colony forming efficiency (CFE) of MK cells, whereas bovine serum albumin increased the CFE 4.5-fold and stimulated the growth rate as well. The addition of impure commercial preparations of platelet-derived growth factor inhibited the CFE and induced the morphological features of squamous terminally-differentiating keratinocytes. As reported in other systems, transforming growth factor beta (TGF-beta) inhibited the growth of secondary keratinocytes in a dose-dependent manner. Thus, at least three factors present in FBS inhibited growth whereas others were stimulatory. These observations explain the difficulties in obtaining replicating subcultures of mouse keratinocytes in serum-supplemented media and emphasize the importance of a serum-free system for studies on growth control and carcinogenesis in keratinocytes.
 ...
PMID:Effects of serum and serum-derived factors on growth and differentiation of mouse keratinocytes. 242 43

The macrocyclic lactone bryostatin 1 activates protein kinase C as effectively as the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Nevertheless, there are only certain TPA-effects that can be induced by bryostatin 1. These include stimulation of epidermal DNA synthesis and alkaline phosphatase activity in vivo as well as activation of the Ca2+-independent, phospholipid-requiring phosphorylation of an epidermal protein in a cell-free system. Various other TPA-effects in vivo and in vitro, which are not mimicked by bryostatin 1 can be inhibited by applying bryostatin 1 30 min prior to TPA. TPA-effects suppressible by bryostatin 1 include the Ca2+-dependent stimulation of arachidonic acid and prostaglandin E2 release, of ornithine decarboxylase (ODC) activity and ODC-mRNA expression and of transglutaminase activity in keratinocytes in vivo and/or in vitro and, in addition, Epstein-Barr virus induction in Raji cells. The same is true for the conversion step (first stage of promotion) of multistage carcinogenesis. In contrast to the TPA induction of arachidonic acid and prostaglandin E2 release and of transglutaminase activity, induction by the Ca2+-ionophore and by high Ca2+-shift, respectively, are not significantly inhibited by bryostatin 1. We suggest that bryostatin 1 might inhibit a specific 'Ca2+-component' of TPA action.
Carcinogenesis 1988 Apr
PMID:Bryostatin 1, an activator of protein kinase C, mimics as well as inhibits biological effects of the phorbol ester TPA in vivo and in vitro. 245 75

Primary human epithelial cells were cotransfected with pHPV-18 and pSV2neo, and cell strains were generated by selecting in G418. One cell strain (FE-A), which exhibits an extended life span, is currently in its 30th passage. In comparison, control cultures can only be maintained up to the seventh passage. Southern blot analysis revealed the presence of at least one intact, integrated viral genome in these cells. FE-A cells showed altered growth properties, characterized by a change in morphology, and clonal density. Differentiation markers analyzed by Western blotting (immunoblotting), such as cytokeratins and involucrin, indicated that the cells resembled a partially differentiated epithelial population. Increased expression of the 40-kilodalton cytokeratin was observed in FE-A cells, similar to that observed in simian virus 40-immortalized human keratinocytes (M. Steinberg and V. Defendi, J. Cell Physiol. 123:117-125, 1985). FE-A cells were also found to be defective in their response to terminal differentiation stimuli. Calcium and 12-O-tetradecanoyl-phorbol-13-acetate treatment induced normal epithelial cells to differentiate, whereas the human papillomavirus 18 (HPV-18)-containing keratinocytes were resistant to these signals, indicating their partially transformed nature. These cells were not able to induce tumors in nude mice over a period of up to 8 months. A second cell strain, FE-H18L, also generated by transfecting HPV-18, also exhibited an extended life span and similar alterations in morphology. Viral RNA transcribed from the early region of HPV-18 was detected in both cell strains by Northern (RNA) blot analysis. These cell strains should provide a useful model for determining the role of HPV in carcinogenesis.
 ...
PMID:Characterization of primary human keratinocytes transformed by human papillomavirus type 18. 245 96


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>