Search PubMed⌕ Search

Biomedical subjects

H Fujiki

Publications and source records attributed to H Fujiki.

At least 163 records · Page 9Linked to original sources
PubMed1989

Codon 61 mutations in the c-Harvey-ras gene in mouse skin tumors induced by 7,12-dimethylbenz[a]anthracene plus okadaic acid class tumor promoters.

Three okadaic acid class tumor promoters, okadaic acid, dinophysistoxin-1, and calyculin A, have potent tumor-promoting activity in two-stage carcinogenesis experiments on mouse skin. DNA isolated from tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) and each of these tumor promoters revealed the same mutation at the second nucleotide of codon 61 (CAA----CTA) in the c-Ha-ras gene, determined by the polymerase chain reaction procedure and DNA sequencing. Three potent 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoters, TPA, teleocidin, and aplysiatoxin, showed the same effects. These results provide strong evidence that this mutation in the c-Ha-ras gene is due to a direct effect of DMBA rather than a selective effect of specific tumor promoters.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Sarcophytols A and B inhibit tumor promotion by teleocidin in two-stage carcinogenesis in mouse skin.

Sarcophytols A and B, isolated from a soft coral, Sarcophyton glaucum, are cembrane-type diterpenes with different numbers of hydroxyl groups. Sarcophytols A and B inhibited tumor promotion by teleocidin in two-stage carcinogenesis experiments on mouse skin. The inhibitory effect of sarcophytol A was demonstrated with two different initiating doses of 7,12-dimethylbenz[a]anthracene (DMBA): 50 micrograms (experiment 1) and 100 micrograms (experiment 2). In experiment 1, three groups of mice were treated with DMBA, and then twice a week with doses (1.6 micrograms, 16 micrograms, and 82 micrograms) of sarcophytol A followed by 2.5 micrograms teleocidin. In week 25, the incidences of tumors in these groups were only 7.1%, 20.0%, and 13.3%, respectively, whereas that in the control group treated with DMBA plus teleocidin was 53.3%. Moreover, at this time, the average numbers of tumors per mouse in these groups were 0.1, 0.3, and 0.3, respectively, while that in the control group was 2.1. In experiment 2 an amount of sarcophytol A (1.6 micrograms) or B (1.7 micrograms) equimolar to 2.5 micrograms teleocidin was applied twice a week, as in experiment 1, and results showed that sarcophytol B also inhibited tumor promotion by teleocidin. Both sarcophytols A and B caused delay in onset of tumor formation, and reduced the percentage of tumor-bearing mice and the average number of tumors per mouse. The effective concentrations of sarcophytols A and B were in the microgram range with an equimolar amount of teleocidin.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Flat reversion by okadaic acid of raf and ret-II transformants.

Okadaic acid is a non-phorbol 12-myristate 13-acetate (PMA)-type tumor promoter on mouse skin and known to be a potent inhibitor of serine/threonine protein phosphatases. Contrary to expectation from its tumor-promoting activity, okadaic acid was shown to have a potential to revert the phenotypes of cells transformed by raf and ret-II to that of normal cells. Two to 3 days after addition of 8 ng of okadaic acid per ml to the culture medium, raf and ret-II transformants changed to flat cells and gained contact inhibition. The amount of fibronectin, which was decreased in malignant transformed cells, was increased in the flat revertants. Moreover, okadaic acid caused a dose-dependent loss of ability to grow in soft agar. The morphology of the cells reverted to malignant phenotype within 1 week after removal of okadaic acid. The levels of mRNA and protein of activated c-raf in flat revertants were similar to those in parental transformed cells. The level of mRNA of ret-II was also not changed by flat reversion. No induction of flat reversion was observed with okadaic acid tetramethyl ether, an inactive compound, or a phorbol ester, PMA. As okadaic acid is a potent inhibitor of protein phosphatases 1 and 2A, the possibility that these phosphatases are involved in signal transduction from the raf and ret-II oncogenes is suggested.

Animals↗
PubMed1989

Phosphorylation at threonine-654 is not required for negative regulation of the epidermal growth factor receptor by non-phorbol tumor promoters.

Phosphorylation of the epidermal growth factor (EGF) receptor following activation of protein kinase C appears to negatively regulate EGF binding and the receptor-associated tyrosine kinase activity. We have identified two agents, the calcium ionophore A23187 and the non-phorbol tumor promoter thapsigargin, that similarly inhibit the EGF receptor binding and kinase activities through protein kinase C-independent pathways. Both agents activate protein kinases that phosphorylate the EGF receptor in A431 cells. To test the hypothesis that negative regulation of the EGF receptor always occurs through phosphorylation of threonine-654, a site uniquely phosphorylated by protein kinase C, we analyzed the tryptic phosphopeptides of EGF receptors isolated from cells treated with these agents. While limited phosphorylation of threonine-654 results from the A23187 treatment, no significant phosphorylation of this residue is detected after thapsigargin treatment. These results suggest that EGF receptor phosphorylation is a general mechanism for altering receptor properties and that site(s) of phosphorylation other than threonine-654 may negatively regulate the kinase activity as well as the binding of the EGF receptor.

Calcimycin↗
PubMed1989

The tumor promoters 12-O-tetradecanoylphorbol-13-acetate and okadaic acid differ in toxicity, mitogenic activity and induction of gene expression.

Okadaic acid (OA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) are both potent tumor promoters in a mouse skin carcinogenesis experiment. OA was much more toxic than TPA for murine embryo cell lines such as Swiss 3T3 cells or C3H10T1/2 cells. TPA is a potent mitogen for 3T3 cells; in contrast OA was unable to stimulate DNA synthesis in these cells. TPA induces a family of primary response genes, the TPA induced sequence (TIS) genes, in a wide variety of cells. Although OA induced modest levels of TIS mRNA expression, the time course of the induction of TIS1 and TIS8 mRNA was delayed when compared to induction by TPA or peptide mitogens such as fibroblast growth factor (FGF). In addition TPA-mediated down-regulation of protein kinase C attenuated TIS gene induction by OA, but not by FGF.

Animals↗
PubMed1989

Inhibitory effect of (-)-epigallocatechin gallate on carcinogenesis with N-ethyl-N'-nitro-N-nitrosoguanidine in mouse duodenum.

(-)-Epigallocatechin gallate (EGCG) is the main polyphenolic constituent of green tea infusion and inhibits tumor promotion by teleocidin in two-stage carcinogenesis on mouse skin. In this work, EGCG was found to inhibit tumor promotion in the gastrointestinal tract in a model system of mouse duodenal carcinogenesis with N-ethyl-N'-nitro-N-nitrosoguanidine. The duodenal tumors that developed were studied stereomicroscopically and histologically.

Animals↗
PubMed1988

Thapsigargin, a novel promoter, phosphorylates the epidermal growth factor receptor at threonine 669.

Thapsigargin, a protein kinase C-independent tumor promoter, can negatively regulate the epidermal growth factor (EGF) receptor through inhibition of high affinity EGF binding and EGF-stimulated tyrosine kinase activity. In contrast to activators of protein kinase C, thapsigargin does not induce significant phosphorylation of threonine 654. However, thapsigargin does stimulate phosphorylation of the EGF receptor at other serine and threonine residues. We now identify threonine 669 as the major site of phosphorylation on the EGF receptor resulting from thapsigargin treatment. These results raise the possibility that phosphorylation of threonine 669 may mediate changes in the binding and kinase state of the EGF receptor.

Amino Acid Sequence↗
PubMed1988

A new tumor promoter from the seed oil of Jatropha curcas L., an intramolecular diester of 12-deoxy-16-hydroxyphorbol.

A new type of phorbol ester, which has a macrocyclic dicarboxylic acid diester structure, was isolated from the seed oil of Jatropha curcas L. (Euphorbiaceae). Based on the results of spectroscopic analyses of the compound and its chemical degradation products, its structure is proposed to be an intramolecular 13,16-diester of 12-deoxy-16-hydroxyphorbol, 12-deoxy-16-hydroxyphorbol-4'-[12',14'-butadienyl]-6'-[16',18',20' - nonatrienyl]-bicyclo[3.1.0]hexane-(13-O)-2'-[carboxylate]-(16-O)-3 '- [8'-butenoic-10']ate (DHPB). DHPB showed slightly weaker biological and biochemical activities than 12-O-tetradecanoylphorbol-13-acetate (TPA). DHPB induced ornithine decarboxylase in mouse skin (2.8 nmol CO2/30 min/mg protein/34 nmol application), inhibited the specific binding of [3H]-12-O-tetradecanoylphorbol-13-acetate to phorbol ester receptors (50% effective dose, 17.0 nM), and activated protein kinase C in vitro (50% effective dose, 36.0 nM). Also, a weak tumor-promoting activity of DHPB was found in a two-stage carcinogenesis experiment on mouse skin. One week after initiation of mice with 100 micrograms of 7,12-dimethyl-benz(a)anthracene, topical application, twice a week, of 2 micrograms of DHPB until week 17, followed by application of 5 microgram of DHPB until week 30 at the same rate, resulted in 46.7% incidence of tumors by week 30. The groups treated with 7,12-dimethylbenz(a)anthracene alone or DHPB alone did not produce significant numbers of tumors. These results indicate that the new phorbol ester, DHPB, is a tumor promoter with weaker activity than 12-O-tetradecanoylphorbol-13-acetate.

Animals↗
PubMed1988

Inhibition by gossypol of tumor promoter-induced arachidonic acid metabolism in rat peritoneal macrophages.

Rat peritoneal macrophages were prelabeled with [3H]arachidonic acid. The release of radioactivity into the medium was increased by treatment with TPA-type tumor promoters, such as TPA, teleocidin and aplysiatoxin, and the non-TPA-type tumor promoter, thapsigargin. Gossypol, at concentrations of 3 and 10 microM, inhibited the release of radioactivity stimulated by both types of tumor promoter, although the mechanism of stimulation of arachidonic acid metabolism is different in the two types of tumor promoter. Stimulation of prostaglandin E2 production by these tumor promoters was also inhibited by treatment with gossypol. Calcium ionophore A23187-stimulated release of radioactivity and prostaglandin E2 production were also inhibited by gossypol treatment. The mechanism of inhibition by gossypol of prostaglandin E2 production is discussed.

Animals↗
PubMed1988

Similar, potent tumor-promoting activity of all isomers of teleocidins A and B in a two-stage carcinogenesis experiment on the skin of CD-1 mice.

Teleocidin, isolated from mycelia of Streptomyces mediocidicus is a mixture of two teleocidin A isomers with molecular weights of 437 (A-1 and A-2) and four teleocidin B isomers with molecular weights of 451 (B-1, B-2, B-3, and B-4). Previously we found that each purified isomer of teleocidins A and B had approximately the same activity as teleocidin in an irritant test on mouse ear, in inductions of ornithine decarboxylase in mouse skin and adhesion of human promyelocytic leukemia (HL-60) cells, and in inhibition of the specific binding of [3H]-12-O-tetradecanoylphorbol-13-acetate to a mouse skin particulate fraction. This paper reports the strong activation of protein kinase C in vitro by each isomer of teleocidins A and B at a concentration of 1 microgram/ml. Detailed studies on the potent tumor promoting activities of the two teleocidin A isomers and four teleocidin B isomers in a two-stage carcinogenesis experiment on mouse skin are also reported, including histological findings on the tumors. Treatment of mice with 100 micrograms of 7,12-dimethylbenz(a)anthracene and then 2.5 micrograms of any one of the six isomers of teleocidins A and B twice a week induced tumors in 80.0 to 91.7% of the mice with 2.8 to 5.2 tumors/mouse in week 30. Scarcely any tumors developed in groups treated with 7,12-dimethylbenz(a)anthracene or any one of the isomers of teleocidins A or B alone. The percentages of incidences of mice bearing papillomas and carcinomas in the six groups treated with 7,12-dimethylbenz(a)anthracene plus one isomer of teleocidins A or B were 90.9 to 98.3% and 1.7 to 9.1%, respectively. These results indicate that all of the isomers of teleocidins A and B have potent tumor promoting activity on mouse skin, irrespective of the structural differences between teleocidins A-1 and A-2, and among the four isomers of teleocidin B. The structure-activity relationship of teleocidins A and B is discussed on the basis of our recent results. Based on the structures of related compounds, we propose a revised numbering system for compounds of the teleocidin class.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Specific binding of [3H]retinoids to cellular retinoid-binding proteins.

The specific binding of [3H]retinoids to cellular retinoid-binding proteins was measured directly by the cold acetone filtration method. After incubation of purified cellular retinoid-binding proteins with [3H]retinoids with or without competitors for 2-4 h, bound ligands were separated from free by filtration using cold acetone. Nonspecific binding of the ligands was reduced sufficiently to allow measurement of specific binding of [3H]retinoids to cellular retinoid-binding proteins. This method has the advantages of being rapid and practical and giving reproducible results.

Adrenal Glands↗
PubMed1988

Hyperphosphorylation of N-60, a protein structurally and immunologically related to nucleolin after tumour-promoter treatment.

Okadaic acid, a non-TPA-type tumour promoter, induces hyperphosphorylation of a 60-kd protein in primary human fibroblasts. Treatment with TPA-type tumour promoters (e.g. TPA and teleocidin) did not cause this hyperphosphorylation. Phosphorylation of this protein was not seen at times earlier than 90 min after the addition of 75 ng/ml okadaic acid to the proliferating cell cultures. The presence of inhibitors such as actinomycin D and cycloheximide, did not significantly influence the level of hyperphosphorylation induced by okadaic acid treatment. By immunoblotting using an antibody anti-nucleolin, the 60-kd protein was identified as a fragment of nucleolar protein, nucleolin. Similarly, antibodies against the 60-kd protein cross-reacted with nucleolin. Furthermore peptide mapping, using staphylococcal V8 protease, showed that the 60-kd protein phosphorylated by casein kinase II in vitro and the okadaic-acid-induced hyperphosphorylated 60-kd protein exhibited identical phosphopeptide maps, indicating that there is also structural relatedness between N-60 and nucleolin. Hyperphosphorylation of the nucleolin fragment (N-60) was suppressed by anti-tumour promoter retinoic acid.

Carcinogens↗
PubMed1988

Inhibition of ornithine decarboxylase induction by retinobenzoic acids in relation to their binding affinities to cellular retinoid-binding proteins.

Retinobenzoic acids induce differentiation of human promyelocytic leukemia cells (HL-60). Like retinoic acid, 14 retinobenzoic acids inhibited the induction of ornithine decarboxylase (ODC) by teleocidin in mouse skin. The mechanism(s) of inhibition of ODC induction by 7 retinobenzoic acids, Am 80, Am 81, Am 580, Am 590, Am 68, Sa 80, and Ch 55 was compared with those by all-trans-retinoic acid and the arotinoid compound 19. Application of 114 nmol of Am 80, Am 81, Am 580, Am 590, Am 68, Sa 80, or Ch 55, 10 min before 11.4 nmol of teleocidin, resulted in 76.7%, 82.0%, 76.2%, 28.3%, 48.4%, 58.6%, and 85.1% inhibition of ODC induction, respectively. Since all-trans-retinoic acid and compound 19 were also inhibitory, we determined whether retinobenzoic acids bind to cellular retinoic acid-binding protein (CRABP) isolated from bovine adrenal glands. Am 80 and Am 580 inhibited the specific binding of 3H-retinoic acid to CRABP, but also showed less affinity than authentic unlabeled retinoic acid and compound 19. Am 81, Am 590, Am 68, Sa 80, and Ch 55 at up to 10 microM were not effective competitors of the binding of either 3H-retinoic acid or 3H-retinol. These results suggest that the inhibition of ODC induction can be mediated by pathways that do not involve CRABP or the cellular retinol-binding protein.

Animals↗
PubMed1988

A radioimmunoassay for palytoxin.

Palytoxin, labelled with 125I-Bolton-Hunter reagent on its terminal amino group, bound specifically to rabbit anti-palytoxin. The extent of binding increased progressively with repeated immunizations. After absorption of the rabbit IgGs with a goat anti-rabbit IgG, binding was reduced greater than 95%. For 50% inhibition of binding in the 125I-palytoxin-antipalytoxin reaction 0.27 pmoles of unlabelled palytoxin was required. Maitotoxin, teleocidin, okadaic acid, debromoaplysiatoxin and 12-O-tetradecanoylphorbol-13-acetate, when tested at 10-100-fold higher concentrations than palytoxin did not affect binding. Palytoxin's serologic activity was stable after 60 min exposure to 100 degrees C and after 60 min exposure to 0.1 N HCl at 50 degrees C, but its capacity to stimulate the arachidonic acid metabolism of rat liver cells was reduced after the 60 min exposure to 0.1 N HCl treatments at 35 degrees C or 0.01 N HCl at 50 degrees C. The average binding constant (K0) as determined by separation of antibody-bound palytoxin from free palytoxin by the double antibody technique was 4.9 x 10(9) M-1 at 0 degrees C. This apparent average association constant increased with increasing temperature suggesting that palytoxin's epitope, most likely hydrophilic, is bound to H2O and the H2O is displaced before binding to the antibody's paratope.

Acrylamides↗
PubMed1988

Production of antibodies and development of a radioimmunoassay for okadaic acid.

An okadaic acid immunogen, prepared by conjugation of okadaic acid to bovine albumin with carbodiimide, was used to immunize two rabbits. The rabbits responded by producing antibodies that neutralized okadaic acid's stimulation of arachidonic acid metabolism and this neutralization increased during the course of immunization. The immune sera bound 3H-okadaic acid and this binding also increased with repeated immunization. After absorption of the rabbit IgG with a goat anti-rabbit IgG, binding was reduced greater than 99%. The binding of okadaic acid to the antibodies in one antiserum was inhibited by as little as 0.2 pmoles of unlabelled okadaic acid. The apparent association constant for binding with this antiserum was 4.17 x 10(9) M-1 (35 degrees C). Maitotoxin, teleocidin, 12-O-tetradecanoylphorbol-13-acetate, aplysiatoxin, palytoxin and brevetoxin B when tested at 29, 228, 168, 169, 3.7 and 112 pmole levels, respectively, did not inhibit binding. The serologic and biological activities of okadaic acid after incubation for 60 min in 0.01 N HCl at 35 degrees C or at 100 degrees C at pH 7.2 were unaffected.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

A receptor model for tumor promoters: rational superposition of teleocidins and phorbol esters.

Four 12-O-tetradecanoyl-13-O-acetylphorbol-type tumor promoters--teleocidin, phorbol ester, aplysiatoxin, and ingenol ester--are superposed in an attempt to understand their common biological activity on the assumption that they may bind to the same receptor site. A method using three-dimensional computer graphics was applied for superposing molecules and receptor mapping. The main feature of the method is that molecules are superposed in terms of spatial arrangement of physical and chemical properties but not in terms of the atomic positions as in conventional methods. This led to successful extraction of common structural features required for potent tumor-promoting activity: two hydrogen donors, a hydrogen acceptor, and a large lipophilic group. Their mutual spatial arrangements are most important for biological activity.

Caenorhabditis elegans Proteins↗
PubMed1988

Okadaic acid: an additional non-phorbol-12-tetradecanoate-13-acetate-type tumor promoter.

Okadaic acid is a polyether compound of a C38 fatty acid, isolated from a black sponge, Halichondria okadai. Previous studies showed that okadaic acid is a skin irritant and induces ornithine decarboxylase (OrnDCase; 3-hydroxyl-L-glutamate 1-carboxy-lyase, EC 4.1.1.17) in mouse skin 4 hr after its application to the skin. This induction was strongly inhibited by pretreatment of the skin with 13-cis-retinoic acid. A two-stage carcinogenesis experiment in mouse skin initiated by a single application of 100 micrograms of 7,12-dimethylbenz[a]anthracene (DMBA) and followed by application of 10 micrograms of okadaic acid twice a week revealed that okadaic acid is a potent additional tumor promoter: tumors developed in 93% of the mice treated with DMBA and okadaic acid by week 16. In contrast, tumors were found in only one mouse each in the groups treated with DMBA alone or okadaic acid alone. An average of 2.6 tumors per mouse was found in week 30 in the group treated with DMBA and okadaic acid. Unlike phorbol 12-tetradecanoate 13-acetate (TPA), teleocidin, and aplysiatoxin, okadaic acid did not inhibit the specific binding of [3H]TPA to a mouse skin particulate fraction when added up to 100 microM or activate calcium-activated, phospholipid-dependent protein kinase (protein kinase C) in vitro when added up to 1.2 microM. Therefore, the actions of okadaic acid and phorbol ester may be mediated in different ways. These results show that okadaic acid is a non-TPA-type tumor promoter in mouse skin carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗