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Biomedical subjects

H Fujiki

Publications and source records attributed to H Fujiki.

At least 235 records · Page 13Linked to original sources
PubMed1984

A rapid, simple screening method for skin-tumor promoters using mouse peritoneal macrophages in vitro.

The enhancing effects in vitro of a potent skin-tumor promoter, phorbol myristate acetate (PMA), and its derivatives on nitroblue tetrazolium (NBT) reduction, phagocytosis and cell spreading of mouse peritoneal macrophages were compared. The enhancing effects on these markers of macrophage function, especially NBT reduction, were found to correlate well with the skin-tumor promoting activities of the phorbol esters. Another potent promoter, teleocidin, strongly enhanced NBT reduction, although teleocidin is structurally different from phorbol esters. Other tumor promoters, namely saccharin, phenobarbital, cantharidin and Tween 60 did not enhance NBT reduction by macrophages. These data indicate that this test system is appropriate for screening of PMA-type tumor promoters such as phorbol esters and teleocidin.

Animals↗
PubMed1984

Tumor promoters block tyrosine-specific phosphorylation of the epidermal growth factor receptor.

Tyrosine-specific phosphorylation of the epidermal growth factor (EGF) receptor in hormonally stimulated A431 cells is blocked by three chemically distinct classes of tumor promoters. Tumor-promoting esters of the diterpene phorbol (phorbol 12-myristate 13-acetate, beta-phorbol 12,13-dibutyrate, and beta-phorbol 12,13-didecanoate), indole alkaloids (teleocidin and lyngbyatoxin A), and polyacetates ( aplysiatoxin and debromoaplysiatoxin ) all inhibited EGF-stimulated phosphorylation of the receptor. Non-tumor-promoting analogs (beta-phorbol, alpha-phorbol 12,13-didecanoate, and hydrolyzed teleocidin) had no effect on the levels of receptor phosphorylation. The ED50 values of the inhibitory effect (0.1-3 ng/ml) reflected the relative tumor-promoting abilities of these compounds in vivo. None of the tumor promoters tested significantly decreased the overall specific binding of 125I-labeled EGF to A431 cells. Scatchard analysis, however, revealed two apparent EGF receptors in this cell type. The dose-responses for tumor-promoter inhibition of EGF receptor tyrosine phosphorylation and high-affinity EGF binding were similar, suggesting that the same initial event is responsible for both effects. This demonstrates a correlation between modulation of EGF receptor binding and phosphorylation of tyrosine by tumor promoters. The data suggest a possible role for protein kinase C, the putative cellular receptor for these tumor promoters, in the mechanism of action.

Amino Acids↗
PubMed1984

Potent antitumor promoting activity of N-6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist, in mouse skin tumor formation induced by 7,12-dimethylbenz[a]anthracene plus teleocidin.

A calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) markedly inhibited the promoting activity of teleocidin on formation of skin tumors in mice initiated by 7,12-dimethylbenz[a]anthracene. This result strongly indicates that the critical action of the Ca2+-calmodulin system is responsible for tumor promotion in mouse skin.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Estimation of tumor promoting activity and structure-function relationships of aplysiatoxins.

Twelve aplysiatoxin compounds have been evaluated as possible tumor promoters in vivo by means of three biological tests: viz. irritation of mouse ear, induction of ornithine decarboxylase in dorsal skin of mice, and inhibition of specific binding of [3H]12-O-tetradecanoylphorbol-13-acetate (TPA) to an epidermal particulate fraction. The potencies of these three biological activities correlate well for each derivative. Bromoaplysiatoxin shows biological activities that are similar to those of the strong tumor promoter, aplysiatoxin. The present studies suggest that the C-3, C-20 and C-30 hydroxyl groups of the aplysiatoxins are involved in binding to the specific receptor of TPA.

Animals↗
PubMed1984

A comparison of the effects of tumor promoters 12-O-tetradecanoylphorbol-13-acetate and teleocidin on gene expression in human skin cell fibroblasts.

The effects on primary human skin fibroblasts of the structurally unrelated tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and teleocidin B were compared with those of epidermal growth factor (EGF) and the non-promoting derivative 4-O-methyl TPA (4-O-MeTPA) by means of two-dimensional gel electrophoresis. Both TPA and teleocidin B caused a marked increase in the synthesis of two polypeptides with molecular weights of 44 kilodaltons (p44) and 55 kilodaltons (p55). P55 was complexed in cell lysates by antiactin antibody and was shown to be a component of the cytoskeleton. P44 migrated very near to actin, but was shown not to be a variant form of actin. No such specific increase in polypeptide synthesis was observed following treatment with either EGF or 4-O-MeTPA, suggesting that the increase in synthesis of p44 and p55 is specific to TPA and teleocidin, both agents with strong promoting activities.

Autoradiography↗
PubMed1984

Studies on olivoretins indicate a requirement for a free hydroxyl group for teleocidin B activity.

Three olivoretins, A, B and C (isolated from Streptoverticillium olivoreticuli), which are O-methylated teleocidin B isomers, were found to be biologically inactive. A fourth olivoretin, D, which has a free hydroxyl group and is identical to one of the four teleocidin B isomers, teleocidin B-4 (teleocidin B of Hirata) was biologically active. These findings indicate that the free primary hydroxyl group of teleocidin B isomers is necessary for activity. The effect on biological activity of the structural difference between des-O-methylolivoretin B (teleocidin B-1) and des-O-methylolivoretin C was also studied.

Animals↗
PubMed1984

Structure-activity studies on synthetic analogues (indolactams) of the tumor promoter teleocidin.

Synthetic analogues (indolactams) related to the tumor promoter teleocidin were synthesized chemically. Of four indolactam-Vs lacking the monoterpenoid moiety of native teleocidin, (-)-indolactam-V bound to the 12-O-tetradecanoylphorbol-13-acetate receptor in cell membranes and induced both adhesion of HL-60 cells and ornithine decarboxylase activity in mouse skin, although its effects were weaker than those of teleocidin. (+)-Indolactam-V and two isomers of epi-indolactam-V showed no induction of ornithine decarboxylase. These results indicate that the S,S configuration of native teleocidin at the isopropyl residue and the hydroxymethyl group is necessary for activity.

Animals↗
PubMed1984

Interaction between quercetin and Ca2+-calmodulin complex: possible mechanism for anti-tumor-promoting action of the flavonoid.

Quercetin was found to have similar inhibitory effects on tumor promoter-induced phenomena to those of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist. Moreover, quercetin was shown to interact directly with the Ca2+-calmodulin complex. These results suggest that quercetin may act as a calmodulin antagonist, and that its antagonistic effect on calmodulin may be important in its anti-tumor-promoting action in vivo.

Animals↗
PubMed1983

Bromine residue at hydrophilic region influences biological activity of aplysiatoxin, a tumor promoter.

Aplysiatoxin and debromoaplysiatoxin, which are isolated from the seaweed, Lyngbya gracilis, differ in their chemical structure only by the presence or absence of a bromine residue in the hydrophilic region. The function and the structure-activity relation of the hydrophilic region are not known. Aplysiatoxin increased malignant transformation, stimulated DNA synthesis, and inhibited the binding of phorbol-12,13-dibutyrate and epidermal growth factor to cell receptors. Debromoaplysiatoxin inhibited the binding of these two substances as strongly as aplysiatoxin but did not increase malignant transformation or stimulate DNA synthesis. These results indicate that a slight change in the chemical structure of the hydrophilic region of aplysiatoxin affects its abilities to increase cell transformation and stimulate DNA synthesis and that the abilities of the tumor promoters to inhibit the binding of phorbol-12,13-dibutyrate and epidermal growth factor are dissociable from their abilities to increase cell transformation and stimulate DNA synthesis under some circumstances.

Animals↗
PubMed1983

Insulinotropic effect of the tumor promoter teleocidin in isolated pancreatic islets.

A tumor promoter teleocidin induced insulin secretion from isolated pancreatic islets in a concentration-dependent manner. The teleocidin-induced secretion was inhibited by p-bromophenacyl bromide, nordihydroguaiaretic acid, 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline and 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone, but not by indomethacin. Insulinotropic concentrations of teleocidin stimulated 6-keto-prostaglandin F1 alpha release from pancreatic islets. These results suggest that phospholipase A2 activation and lipoxygenase product(s) are involved in the mechanism of teleocidin-induced insulin secretion.

Alkaloids↗
PubMed1983

Sphingomyelin is a possible constituent of binding sites for the tumor promoters phorbol ester, indole alkaloids and polyacetates.

Specific binding of 12-0-tetradecanoylphorbol-13-acetate to the epidermal particulate fraction was susceptible to phospholipase A2 and phospholipase C, but was almost resistant to protease and completely resistant to a mixture of several glycosidases. Of vesicles prepared from five phospholipids associated with the epidermal particulate fraction, sphingomyelin vesicles bound 12-0-tetradecanoylphorbol-13-acetate specifically and most effectively. This binding was inhibited by not only phorbol esters but also two other classes of tumor promoters, indole alkaloids and polyacetates. These results suggest that sphingomyelin is involved in the binding sites of tumor promoters to the cell membrane.

Acetates↗
PubMed1983

A new tumor promoter, dihydroteleocidin B, enhances cell growth and the production of murine leukemia virus by fibroblasts.

The effects of tumor promoters on the expression of murine leukemia virus (MuLV) were studied in tissue culture. Dihydroteleocidin B, an indole alkaloid, recently found to be a tumor promoter, enhanced not only the production of Moloney MuLV (M-MuLV) by a mouse fibroblast cell line, C3H2K, persistently infected with M-MuLV, but also growth on the C3H2K cells. The production of infectious M-MuLV by M-MuLV-infected C3H2K cells that had been treated with dihydroteleocidin B for 1-7 days was four or five times higher than that of control cells. C3H2K cells grew faster and became stationary at higher cell densities in the presence of dihydroteleocidin B than in its absence. The tumor-promoting phorbol ester phorbol-12, 13-didecanoate and 12-O-tetradecanoylphorbol-13-acetate also enhanced the production of M-MuLV, but their effects were not so strong as that of dihydroteleocidin B. These tumor promoters, however, did not induce production of endogenous MuLV in C3H2K or K-BALB cells.

Alkaloids↗
PubMed1983

Activation of the EBV-cycle and aggregation of human blood lymphocytes by the tumor promoters teleocidin, lyngbyatoxin A, aplysiatoxin and debromoaplysiatoxin.

A variety of tumor promoters such as the phorbol esters were found to be capable of inducing the viral cycle in cell lines latently infected with Epstein-Barr virus (EBV). We tested two classes of new tumor promoters; indole alkaloids and polyacetates, for their ability to induce the synthesis of the Epstein-Barr virus determined early antigen (EA) complex. Teleocidin and lyngbyatoxin A are indole alkaloids. Aplysiatoxin and debromoaplysiatoxin are polyacetates. Of these four tumor promoters all but debromoaplysiatoxin induced the synthesis of the EA complex. However, in combination with 3 mM n-butyrate, all four induced EA synthesis. The potent tumor promoters teleocidin, lyngbyatoxin A and aplysiatoxin induced maximal synthesis of EA at the concentration of 5 to 10 ng/ml, whereas the weak tumor promoter debromoaplysiatoxin required a concentration of 250 ng/ml to achieve maximal induction. Phorbol esters induce quick morphological changes and aggregation of human blood lymphocytes. The latter phenomenon has been interpreted as the expression of a "cell binding phenotype" (Patarroyo et al., in press). We showed that all four promoters induced aggregation of human lymphocytes at similar concentrations. The induction seemed to be a common effect which could be induced by both strong and weak tumor promoters.

Alkaloids↗
PubMed1983

Teleocidin-induced modulation of growth and cell interaction in microenvironment-dependent mouse leukemias.

Teleocidin is a new tumor-promoting substance chemically unrelated to phorbol groups. Its biological effects on thymic microenvironment-dependent leukemias derived from AKR spontaneous leukemias were studied in vitro in comparison with 12-O-tetradecanoylphorbol 13-acetate (TPA), a representative tumor promoter of the phorbol group. Teleocidin stimulated the in vitro growth of 21 out of 31 symbiotic cell lines in the absence of growth-supporting stromal cells. All the responders to teleocidin were responsive also to TPA and the degree of growth stimulation in each cell line was comparable. Both promoters could inhibit the symbiotic complex formation with thymic epithelial cells probably by affecting the cytoskeleton. All symbiotically cultured AKR leukemia cells expressed Thy-1.1 antigen, but their expression of Lyt-1.2 and Lyt-2.1 was heterogenous. There was no direct correlation between teleocidin-responsiveness and Lyt-phenotypes of the leukemia cells.

Alkaloids↗
PubMed1983

Role of flavonoids in suppressing the enhancement of phospholipid metabolism by tumor promoters.

Quercetin, a ubiquitous flavonoid in plants, inhibited the incorporation of [32P]inorganic phosphate (32Pi) into phospholipid of HeLa cells enhanced by 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent tumor promoter. Among the flavonoids tested, luteolin was the most effective in inhibiting the action of TPA. Studies on structure-activity relationships demonstrated that more hydroxylated flavones and flavonols had stronger inhibitory effects. Quercetin and luteolin also inhibited enhancement of 32Pi-incorporation into phospholipid by dihydroteleocidin B, another potent tumor promoter. The inhibitory effect of quercetin on the biological action of tumor promoters is interesting in relation to the non-carcinogenicity of this flavonoid in animals, in spite of its mutagenicity.

Drug Interactions↗
PubMed1983

Enhanced incorporation of radioactive inorganic phosphate into phospholipids of HeLa cells by tumor promoters.

Teleocidin, a new tumor promoter, increased incorporation of radioactive inorganic phosphate (32Pi) into phospholipids in HeLa cells. This effect was detected within 1 h on incubation of the cells in medium containing teleocidin. The half-maximum effective dose of teleocidin was approximately 10 ng/ml. The main effect of teleocidin was on the incorporation of 32Pi into the phosphatidylcholine fraction, with a lesser effect on 32Pi incorporation into other phospholipid fractions. Increased incorporation of 32Pi into phospholipids was also observed on incubation of the cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), dihydroteleocidin B, or lyngbyatoxin A, which are all complete tumor promoters, and also with mezerein, which is an incomplete and second stage promoter. On the other hand, at concentrations of up to 1 microgram/ml, 4-O-methyl TPA and Ca2+ ionophore A23187, which are incomplete and first stage promoters, and phorbol, which has no promoting activity in skin carcinogenesis, did not cause any increased incorporation of 32Pi into phospholipid fractions of HeLa cells.

Alkaloids↗