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E Huberman

Publications and source records attributed to E Huberman.

At least 19 recordsLinked to original sources
PubMed1979

The importance of the "bay region" diol-epoxide in 7,12-dimethylbenz[a]anthracene skin tumor initiation and mutagenesis.

The skin tumor-initiating and V79 mutagenic activities of various derivatives of 7,12-dimethylbenz[a]anthracene (DMBA) were investigated to determine what possible cellular metabolite(s) may be responsible for its carcinogenicity and/or mutagenicity. 1-,2-,3-,4- and 5-hydroxyDMBA were found to be essentially inactive as skin tumor initiators whereas 9- and 10-hydroxyDMBA had weak activity. The (+/-)-trans DMBA 8,9- and 5,6-dihydrodiols were also essentially inactive as skin tumor initiators and (+/-)-DMBA 8beta,9alpha-diol-10alpha-11alpha-epoxide had weak skin tumor initiating activity. All of the above tested derivatives of DMBA were essentially inactive as mutagens in the cell-mediated or direct V79 mutagenesis systems. A methyl or fluoro addition to the 1, 2 or 5 positions almost completely blocked the skin tumor initiating and V79 mutagenic activities of DMBA, whereas a fluoro addition to position 11 did not. From our data we suggest that a 'bay region' diol-epoxide may be important in DMBA carcinogenicity and mutagenicity.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Identification of 7,12-dimethylbenz[a]anthracene metabolites that lead to mutagenesis in mammalian cells.

The mutagenicity of 7,12-dimethylbenz[a]-anthracene (DMBA) and 11 of its enzymatically derived metabolites was tested with Chinese hamster V79 cells for identification of mutagenic metabolites. The metabolites consisted of 7-hydroxymethyl-12-methylbenz[a]anthracene, 7-methyl-12-hydroxymethylbenz[a]anthracene, 7,12-dihydroxymethylbenz[a]anthracene, three trans-3,4-diols, two trans-5,6-diols, and three trans-8,9-diols, all of which derived from DMBA or from the hydroxymethyl derivatives. Mutations were characterized by resistance to ouabain and 6-thioguanine. None of the tested metabolites were mutagenic in V79 cells, which do not metabolize polycyclic aromatic hydrocarbons. Therefore, mutagenesis in the V79 cells was tested in the presence of golden hamster cells capable of metabolizing polycyclic aromatic hydrocarbons (cell-mediated assay). In this assay, DMBA, 7-hydroxymethyl-12-methylbenz[a]anthracene, 7-methyl-12-hydroxymethylbenz[a]anthracene, and their trans3,4-diols were mutagenic for both genetic markers, and the mutagenic response increased as a function of the hydrocarbon dose. All other metabolites were either inactive or showed up to a 4-fold higher mutation frequency than the untreated V79 cells for ouabain and 6-thioguanine resistance. The DMBA-trans-3,4-diol was the only metabolite that was more active than DMBA itself; at 0.05 muM it was 6-8 times more active than DMBA itself; at 0.05 muM it was 6-8 times more active than DMBA in inducing both ouabain and 6-thioguanine resistance. This diol was mutagenic at a dose as low as 0.01 muM. Mutagenesis by DMBA and the trans-3,4-diols was inhibited by 7,8-benzoflavone, an inhibitor of mixed-function oxidases. Analysis of DMBA metabolism in intact golden hamster cells indicated that DMBA-trans-3,4-diol is one of the major metabolites produced. Our results therefore suggest that DMBA-trans-3,4-diol may be metabolized to a diol-epoxide, presumably the trans-3,4-diol-1,2-epoxide, which may be a major reactive metabolite responsible for DMBA mutagenicity in mammalian cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Induction of terminal differentiation in human promyelocytic leukemia cells by tumor-promoting agents.

Human promyelocytic leukemia cells (HL-60) were induced to differentiate into mature cells by the tumor-promoting agent phorbol-12-myristate-13-acetate and other related phorbol diesters. Differentiation was determined by an increase in the percent of myelocytes, metamyelocytes, and other mature myeloid cells as well as by an increase in the percent of phagocytizing cells. Induction of differentiation could be determined after 2 days of treatment with phorbol-12-myristate-13-acetate at a dose as low as 6 X 10(11) M. A correlation was found between reported tumor-promoting activity of a series of phorbol esters and their ability to induce myeloid differentiation and to inhibit cell growth. It is suggested that tumor-promoting agents like chemicals that induce terminal differentiation in these cells, at extremely low concentrations, may be used as a tool in the study of the control of cell growth, cell differentiation, and malignancy in human leukemic cells.

Cell Differentiation↗
PubMed1979

gamma-Glutamyl transpeptidase and malignant transformation of cultured liver cells.

The relationship between gamma-glutamyl transpeptidase (GGT)and malignant cell transformation was analyzed in malignant and nonmalignant culture epithelial cell lines derived from rat livers and fibroblastic cell types derived from hamsters and mice. GGT activity was prominent (25 to 90% of cells) in 3 of 5 malignant epithelial liver cell lines. None of the 9 fibroblastic or 4 nonmalignant epithelial cell lines exhibited GGT activity. Our results suggest that by use of GGT activity we can detect in cultured liver cells a significant fraction of the spontaneously or chemically induced malignant cells. Thus, in conjunction with other markers, this marker may help in identifying tumorigenic cells in liver epithelial cultures.

Animals↗
PubMed1979

Maintenance of adult rat hepatocytes on C3H/10T1/2 cells.

A procedure is described for maintaining primary cultures of adult rat hepatocytes on a layer of irradiated C3H/10T1/2 cells. These hepatocytes were capable of metabolizing the liver carcinogen N-2-acetylaminofluorene to water-soluble products and after 14 days in culture could still metabolize approximately 70% of the Day 1 level. Hepatocytes maintained on the C3H/10T1/2 cells were inducible for the liver-specific enzyme tyrosine aminotransferase, and exhibited approximately a 4-fold induction by hydrocortisone during a 10-day culture period. Morphologically, these hepatocytes retained many characteristics of hepatocytes in vivo. By contrast, hepatocytes maintained on plastic lost both N-2-acetylaminofluorene-metabolizing ability and tyrosine aminotransferase activity by Day 5. This was presumably due to degeneration of the hepatocytes and an overgrowth by fibroblasts. The maintenance of morphologically and biochemically functional hepatocytes in culture on feeder cells may provide a valuable approach for studying drug metabolism and liver cell transformation in vitro.

2-Acetylaminofluorene↗
PubMed1979

Stimulation of differentiated functions in human melanoma cells by tumor-promoting agents and dimethyl sulfoxide.

Treatment of cultured human HO melanoma cells with the mouse skin tumor promoter phorbol-12-myristate-13-acetate (PMA) at 5 x 10(-10) to 5 x 10(-7) M resulted in a dose-related inhibition of growth and a stimulation of differentiated functions. These included melanin synthesis and formation of dendrite-like structures. Higher doses of phorbol dibutyrate, a less potent tumor promoter, were required to produce an effect comparable to that of PMA for dendrite induction. Phorbol and two other phorbol esters, which lack tumor-promoting activity, were either inactive or elicited a poor response. In addition to morphological changes, treatment with PMA altered glucosamine incorporation into membrane gangliosides. After PMA treatment, glucosamine incorporation increased 8- to 10-fold in the GM3 ganglioside and decreased 2-fold in the GM1 ganglioside, as compared to phorbol or untreated control. Inhibition of cell growth and stimulation of melanin synthesis were also observed after treatment of the HO cells with dimethyl sulfoxide. Unlike the tumor-promoting agents, dimethyl sulfoxide did not induce the formation of dendrite-like structures in the cells. These findings indicate that HO melanoma cells can be stimulated into terminally differentiated cells after treatment with tumor-promoting agents such as phorbol diesters.

Cell Differentiation↗
PubMed1978

Mutagenicity to mammalian cells in culture by (+) and (-) trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrenes and the hydrolysis and reduction products of two stereoisomeric benzo(a)pyrene 7,8-diol-9,10-epoxides.

The mutagenicity for mammalian cells of benzo(a)pyrene (BP) and 9 of its derivatives was tested by resistance to ouabain in Chinese hamster V78 cells. The derivatives included the (-) and (+) enantiomers of trans-7,8-diol; the racemic (+/-)trans-7,8-diol; two triols, (7/8,9)-triol and (7,9/8)-triol; and four tetrols, (7,10/8,9)-tetrol, (7/8,9,10)-tetrol, (7,9/8,10-triol and (7,9,10/8)-tetrol. Since V78 cells do not metabolize polycyclic hydrocarbons, mutagenesis was tested both in the presence and in the absence of Golden hamster cells capable of metabolizing polycyclic hydrocarbons. Neither BP nor any of its 9 tested derivatives showed mutagenicity for V78 cells in the absence of normal Golden hamster cells. However, in the presence of these cells, BP and the optically active and racemic trans-7,8-diols exhibited a mutagenic response that was dose-dependent. All other derivatives were inactive. The most active mutagenic hydrocarbon was (-) trans-7,8-diol, and activity decreased in the order (+/-)trans-7,8-diol, (+) trans-7,8-diol and BP.

Benzopyrenes↗
PubMed1978

Liver cell-mediated mutagenesis of mammalian cells by liver carcinogens.

A cell-mediated mutagenesis assay using primary cultures of rat liver cells and V79 Chinese hamster cells has been developed. Liver carcinogens and their structural analogues were studied. Mutations in the V79 cells were characterized by resistance to ouabain. Cocultivation of the liver cells and V79 cells in the presence of the carcinogens N-nitrosodimethylamine, N-nitrosodiethylamine, and aflatoxin B1 caused the induction of ouabain-resistant mutants of V79 cells. In the absence of liver cells, the carcinogens did not induce ouabain resistance. The analogues N-nitrosomethyl-tert-butylamine and aflatoxin G2 were not mutagenic. The carcinogens exhibited a dose-dependent enhancement of mutation frequency. The mutation frequency also increased with increasing numbers of liver cells seeded. It is suggested that such an experimental system may be useful for screening for chemical carcinogens.

Adenosine Triphosphatases↗
PubMed1978

Carcinogenicity and mutagenicity of benz(a)anthracene diols and diol-epoxides.

Benz(a)anthracene (BA) and its five possible trans-dihydrodiols were evaluated for determination of their skin tumor-initiating activity and their mutagenic activity in Chinese hamster V79 cells. In addition, the skin tumor-initiating abilities of five diol-epoxides of BA were tested. Results showed (+/-)-trans-3,4-dihydroxy-3,4-dihydrobenz(a)anthracene (BA 3,4-dihydrodiol) to be approximately 10 times more mutagenic than was BA and about 20 times more mutagenic than were the other possible dihydrodiols in the V79 cells cocultivated with irradiated hamster embryo cells. As a skin tumor initiator, BA 3,4-dihydrodiol was approximately 5 times more active than BA, whereas the other BA dihydrodiols were all less active tumor initiators. (+/-)-trans-3alpha,4beta-Dihydroxy-1alpha,2alpha-epoxy-1,2,3,4-tetrahydrobenz(a)anthracene was found to be approximately 20% more active as a tumor initiator than was BA 3,4-dihydrodiol, whereas the other diol-epoxides of BA were less active than BA itself. The results suggest that the bay-region diol-epoxide of BA may be the ultimate carcinogen and mutagenic form of BA.

Animals↗
PubMed1977

DNA binding and its relationship to carcinogenesis by different polycyclic hydrocarbons.

Five different polycyclic hydrocarbons with different degrees of carcinogenicity in vivo were tested for their metabolism to water-soluble products and their binding to DNA, RNA, and protein in normal embryonic hamster and BHK cells. The compounds studied were 7, 12-dimethylbenz(a)anthracene, benzo(a)pyrene, 20-methyl-cholanthrene, dibenz(a,h)anthracene and dibenz(a,c)anthracene. All five compounds were metabolized to water-soluble produces in both types of cells and treatment of cells with aminophylline enhanced this metabolism. After and not before this enhancement of metabolism by aminophylline, there was a relationship between the degree of carcinogenicity and binding to DNA. There was no such relationship with binding to RNA or protein. The results, indicating a relationship between the degree of carcinogenicity and binding to DNA under appropriate conditions of metabolism, support the suggestion that DNA is the target for carcinogenesis by such carcinogens.

Aminophylline↗
PubMed1976

Independent regulation of two types of aryl hydrocarbon (benzo(a)pyrene) hydroxylase in mammalian cells.

Aryl hydrocarbon (benzo(a)pyrene) hydroxylase induced by dibutyryl cyclic AMP (dcAMP), plus aminophylline (AHH I) can be ditsinguished from the hydroxylase induced by benz (a) anthracene (AHH II) by its lower Km for benzo (a) pyrene. Treatment with the combination of benzo (a) anthracene and dcAMP plus aminophylline induced both AHH I and AHH II activities. After optimal induction of AHH II activity by benz (a) anthracene, the addition of dcAMP plus aminophylline gave an induction of AHH I. Although AHH I activity declined to an almost basal level 24 h after treatment with dcAMP plus aminophylline, the addition of benz (a) anthracene prevented this decline. Inducibility by dcAMP plus aminophylline or by benz (a) anthracene varied in different cell lines. Some cell lines were induced by both substances, with a higher induction by benz (a) anthracene, while other lines were inducible only by benz (a) anthracene, and a third cell type was not inducible by either. Selection for resistance to benzo (a) pyrene of a cell line inducible by both compounds resulted in a fourth cell type which was more inducible by dcAMP plus aminophylline than by benz (a) anthracene. The results suggest that there is an independent regulation of hydroxylase AHH I and AHH II and that the induction of these two enzyme activities is determined by different genetic controls.

Aminophylline↗
PubMed1975

Regulation of aryl hydrocarbon (benzo-(A)-pyrene) hydroxylase activity in mammalian cells. Induction of hydroxylase activity by N6,O2'-dibutyryl8 adenosine 3':5'-monophosphate and aminophylline.

Treatment of hamster BHK cells with N6,O2'-dibutyryl adenosine 3':5'-monophosphate (Bt2cAMP), aminophylline, theophylline, or papaverine increased the level of aryl hydrocarbon (benzo(a)pyrene) hydrolxylase activity. The highese increase, 100-fold, was obtained with Bt2cAMP plus aminophylline or theophylline. N2,O2-Dibutyryl guanosine 3':5'-monophosphate gave a lower induction than Bt2cAMP. The level of hydroxylase activity started to decrease 6 hours after treatment with the inducer and was reduced to almost the uninduced level after 24 hours. Repeated addition of Bt2cAMP and aminophylline did not prevent this decrease. The hydroxylase can also be induced by treating cells with benz(a)anthracene, and the level of this induced activity was maintained for 24 hours. Aminophylline gave a 2- to 8-fold stimulation of the induction by benz(a)anthracene. The enzyme activity induced by Bt2cAMP, aminophylline, and benz(a)anthracene converted benzo(a)pyrene to similar alkali-extractable metabolities with a fluorescence spectra similar to that of 3-hydroxybenzo(a)pyrene. These induced enzyme activities also showed a similar heat stability. Induction by Bt2cAMP and aminophylline, like induction by benz(a)anthracene, required continued protein synthesis and only an initial period of RNA synthesis. Compared to the benz(a)anthracene-induced hydroxylase with a Km of 4.3 muM, the hydroxylase induced by Bt2cAMP and aminophylline showed a Km of 0.14 muM, and was 100-fold more sensitive to inhibition by 7,8-benzoflavone. Increasing the serum concentration in the culture medium stimulated the induction by aminophylline but did not stimulate induction by benz(a)anthracene. The results indicate that aryl hydrocaarbon (benzo(a)pyrene) hydroxylase can be induced by compounds that increase the level of adenosine 3':5'-monophosphate and that this induction and induced enzyme activity differs from that caused by benz(a)anthracene.

Aminophylline↗
PubMed1975

Activation of carcinogenic polycyclic hydrocarbons in polyoma-virus-transformed cells as a prerequisite for polyoma virus induction.

Polyoma-virus (PV)-transformed cell clones, which are inducible for virus synthesis by various physical and chemical agents, metabolize the chemically non-reactive carcinogen benzo(a)pyrene (BP) into water soluble products. In cultures of such clones, which metabolize BP to a level of 30-6-% of that of normal cells, up to 10.4% of the cells were induced for PV synthesis by BP, 20-methylcholanthrene (MCA) and 7,12-dimethylbenz(a)anthracene (CMBA). No PV induction was observed with the non-carcinogenic polycyclic hydrocarbons pyrene chrysene and benz(a)-anthracene. A proportion of subclones, isolated from a PV- inducible clone, which metabolized 0.1 mug or less BP per 10-6 cells were all inducible for PV synthesis by these carcinogens. Subclones isolated from an inducible clone pretreated with BP were shown to metabolize less than 0.1 mu BP per 10-6 cells and were resistant to virus induction by the carcinogenic polycyclic hydrocarbons. Benzoflavone, which inhibited the metabolism of BP in clones metabolizing high levels of this carcinogen, also prevented the induction of PV antigen and infectious virus synthesis in these clones. The data indicate a relationship between the carcinogenicity of polycyclic hydrocarbons and their ability to induce virus in the PV-transformed cells and suggest that virus induction depends on metabolic conversion of these hydrocarbons into similar reactive compounds that are responsible for malignant transformation and mutagenesis.

Animals↗